Intelligence enhancing software - continued...

I wanted to bring into this separate post a comment from blog reader Erik, made below. You don't have to own an iPhone and pay six bucks to do the dual-n-back tests. Erik's comment:

Hey. I'd just add that there are some accurate dual-n-back implementations on the web. Ours is open source, and it's here: dual n back implementation . It follows the protocol very closely, and it even got a thumbs up from the researchers.

.

Do our noses sniff danger in the air?

The Grueneberg ganglion is a recently discovered ball of olfactory nerve cells found at the tip of the noses of mammals, including us. It turns out that, in mice, it is responsible for detecting alarm pheromones of the sort that are secreted by both plants and animals to warn conspecifics of a threatening situation. (There is speculation about human pheromones as an factor in emotional state before death). Chang points to some definitive work in mice from Brechbühl et al. Here is their abstract:

Alarm pheromones (APs) are widely used throughout the plant and animal kingdoms. Species such as fish, insects, and mammals signal danger to conspecifics by releasing volatile alarm molecules. Thus far, neither the chemicals, their bodily source, nor the sensory system involved in their detection have been isolated or identified in mammals. We found that APs are recognized by the Grueneberg ganglion (GG), a recently discovered olfactory subsystem. We showed with electron microscopy that GG neurons bear primary cilia, with cell bodies ensheathed by glial cells. APs evoked calcium responses in GG neurons in vitro and induced freezing behavior in vivo, which completely disappeared when the GG degenerated after axotomy. We conclude that mice detect APs through the activation of olfactory GG neurons.

The discovery of structural form

Charles Kemp and Tenenbaum present a computational model that learns structures of many different forms and that discovers which form is best for a given dataset. Their article in PNAS is open access, so you can follow this link to the detailed discussion and figures.

Algorithms for finding structure in data have become increasingly important both as tools for scientific data analysis and as models of human learning, yet they suffer from a critical limitation. Scientists discover qualitatively new forms of structure in observed data: For instance, Linnaeus recognized the hierarchical organization of biological species, and Mendeleev recognized the periodic structure of the chemical elements. Analogous insights play a pivotal role in cognitive development: Children discover that object category labels can be organized into hierarchies, friendship networks are organized into cliques, and comparative relations (e.g., “bigger than” or “better than”) respect a transitive order. Standard algorithms, however, can only learn structures of a single form that must be specified in advance: For instance, algorithms for hierarchical clustering create tree structures, whereas algorithms for dimensionality-reduction create low-dimensional spaces. Here, we present a computational model that learns structures of many different forms and that discovers which form is best for a given dataset. The model makes probabilistic inferences over a space of graph grammars representing trees, linear orders, multidimensional spaces, rings, dominance hierarchies, cliques, and other forms and successfully discovers the underlying structure of a variety of physical, biological, and social domains. Our approach brings structure learning methods closer to human abilities and may lead to a deeper computational understanding of cognitive development.

New software for your iPhone to make you smart

In a previous post I have mentioned the work of Jaeggi et al. who have shown that fluid intelligence, the ability to reason and to solve new problems independently of previously acquired knowledge, can be improved by training of working memory. Now their basic experimental paradigm is available as an iPhone app costing six bucks. I'm playing with it, and it has hooked me, unlike the web based stuff I have described previously. Here is a more thorough presentation of the paradigm of Jaeggi et al. than I gave in the original post:

In this task, participants see two series of stimuli that are synchronously presented at the rate of 3 s per stimulus. One string of stimuli consists of single letters whereas the other consists of individual spatial locations marked on a screen. The task is to decide for each string whether the current stimulus matched the one that was presented n items back in the series. The value of n varies from one block of trials to another, with adjustments made continuously for each participant based on performance. As performance improves, n increments by one item; as it worsens, n decrements by one item. Thus, the task changes adaptively so that it always remained demanding, and this demand is tailored to individual participants. This form of training engages processes required for the management of two simultaneous tasks; it engaged executive processes required for each task; and it discouraged the development of task-specific strategies and the engagement of automatic processes because of the variation in n and because of the inclusion of two different classes of stimuli.


The n-back task that is used as the training task, illustrated for a 2-back condition. The letters are presented auditorily at the same rate as the spatial material is presented visually.

Evolution "for the Good of the Group"

David S. Wilson and Edwin O. Wilson write a very clear summary in American Scientist, with title of this post, of the main features of group selection theory - which describes how natural selection takes place at multiple levels: genes, individuals, group of individuals. Below is an excerpt, and here is the PDF.

To think clearly about group selection, it is important to compare the survival and reproduction of individuals in the right way. The problem with "for the good of the group" behaviors is that they are locally disadvantageous. A prudent member of the herd might gain from conserving resources, but cheaters within the same group gain even more. Natural selection is based on relative fitness. If solid citizens are less fit than cheaters within their own group, then something more is required to explain how they can evolve in the total population. That something is a positive fitness difference at a larger scale. Groups of solid citizens are more fit than groups of cheaters.

Figure - Multilevel selection theory describes a hierarchy of evolutionary processes organized like nested Russian dolls. At the innermost level, within a single organism, genes contend with each other for a place in the next generation; within a group of organisms, selection acts on the relative fitness of individuals; groups within a population also differ in their collective survival and reproduction. Adaptation at any given level tends to be undermined by selection at lower levels. At even higher levels (not shown), populations, multispecies communities and whole ecosystems can be subject to selection.

These interacting layers of competition and evolution are like Russian matryoshka dolls nested one within another. At each level in the hierarchy natural selection favors a different set of adaptations. Selection between individuals within groups favors cheating behaviors, even at the expense of the group as a whole. Selection between groups within the total population favors behaviors that increase the relative fitness of the whole group—although these behaviors, too, can have negative effects at a still-larger scale. We can extend the hierarchy downward to study selection between genes within a single organism, or upward to study selection between even higher-level entities. The general rule is: Adaptation at level X requires a corresponding process of selection at level X and tends to be undermined by selection at lower levels.

This way of thinking about evolution is called multilevel selection (MLS) theory. Although the term "multilevel selection" is newer than the term "group selection," the Russian-doll logic has been present from the beginning, going back to the works of Darwin.

Darwin would not have been motivated to think about group selection were it not for the existence of traits that are selectively disadvantageous within groups. In a famous passage from Descent of Man, he notes that morally upright people do not have an obvious advantage over less-upright people within their own "tribe," but that tribes of morally upright people would robustly outcompete other tribes. He concluded by saying "... and this would be natural selection." Darwin was clearly employing the Russian-doll logic of MLS theory in this passage. He did not comment on the irony that morality expressed within groups can become morally problematic in between-group interactions, but his hypothetical example perfectly illustrates the general rule stated above, which makes adaptations at one level part of the problem at higher levels.

Brain Candy

Daniel Levitin writes a review of "Human - What Makes Us Unique" by Michael S. Gazzaniga which is worth a look. Also, Levitin has new book out which I have just ordered: "The World in Six Songs: How the Musical Brain Created Human Nature." From the Publisher's weekly review:

Charles Darwin meets the Beatles in this attempt to blend neuroscience and evolutionary biology to explain why music is such a powerful force. In this rewarding though often repetitious study by bestselling author Levitin (This Is Your Brain on Music), a rock musician turned neuroscientist, argues that music is a core element of human identity, paving the way for language, cooperative work projects and the recording of our lives and history. Through his studies, Levitin has identified six kinds of songs that help us achieve these goals: songs of friendship, joy, comfort, knowledge, religion and love. He cites lyrics ranging from the songs of Johnny Cash to work songs, which, he says, promote feelings of togetherness. According to Levitin, evolution may have selected individuals who were able to use nonviolent means like dance and music to settle disputes. Songs also serve as memory-aids, as records of our lives and legends. Some may find Levitin's evolutionary explanations reductionist, but he lightens the science with personal anecdotes and chats with Sting and others, offering an intriguing explanation for the power of music in our lives as individuals and as a society.

Note added 8/28... A very negative critical review of this Levitin book, by John Carmody, has just appeared in Nature. Now I'm thinking maybe I shouldn't have ordered it.

Phantom Penises In Transsexuals

In an article in the Journal of Consciousness Studies, Ramachandran and McGeoch offer evidence of an innate gender-specific body image in the brain:

How the brain constructs one’s inner sense of gender identity is poorly understood. On the other hand, the phenomenon of phantom sensations — the feeling of still having a body-part after amputation — has been much studied. Around 60% of men experience a phantom penis post-penectomy. As transsexuals report a mismatch between their inner gender identity and that of their body, we wondered what could be learned from this regarding innate gender-specific body image. We surveyed male-to-female transsexuals regarding the incidence of phantoms post-gender reassignment surgery. Additionally, we asked female-to-male transsexuals if they had ever had the sensation of having a penis when there was not one physically there. In post-operative male-to-female transsexuals the incidence of phantom penises was significantly reduced at 30%. Remarkably, over 60% of female-to-male transsexuals also reported phantom penises. We explain the absence/presence of phantoms here by postulating a mismatch between the brain’s hardwired gender-specific body image and the external somatic gender. Further studies along these lines may provide penetrating insights into the question of how nature and nurture interact to produce our brain-based body image.

Simon LeVay, an expert on human sexuality, does make the point that Ramachandran is comparing those who are extremely pleased with getting rid of their penis to others who are distressed and think about their penis all the time. It would appear that Ramachandran has largely left out emotions, and also the question of wishful thinking.

MindBlog's editorial assistant

It is very difficult to putter with this blog while lounging on my couch - one of my new Abyssianian kittens always helps out or wishes I would play with him instead.

A simple metric to infer personality from facial expression

Oosterhof and Todorov have devised a simple model that uses facial cues that have evolutionary significance to predict important social judgments as a function of two orthogonal dimensions of valence and dominance. Here is a graphic illustrating the essential facial features, followed by their abstract.

People automatically evaluate faces on multiple trait dimensions, and these evaluations predict important social outcomes, ranging from electoral success to sentencing decisions. Based on behavioral studies and computer modeling, we develop a 2D model of face evaluation. First, using a principal components analysis of trait judgments of emotionally neutral faces, we identify two orthogonal dimensions, valence and dominance, that are sufficient to describe face evaluation and show that these dimensions can be approximated by judgments of trustworthiness and dominance. Second, using a data-driven statistical model for face representation, we build and validate models for representing face trustworthiness and face dominance. Third, using these models, we show that, whereas valence evaluation is more sensitive to features resembling expressions signaling whether the person should be avoided or approached, dominance evaluation is more sensitive to features signaling physical strength/weakness. Fourth, we show that important social judgments, such as threat, can be reproduced as a function of the two orthogonal dimensions of valence and dominance. The findings suggest that face evaluation involves an overgeneralization of adaptive mechanisms for inferring harmful intentions and the ability to cause harm and can account for rapid, yet not necessarily accurate, judgments from faces.

Weekly musical offering - Stars & Stripes FOREVER!

Brain changes that correlate with successful dyslexia therapy

Meyler et al. have published an interesting study in Neuropsychologia showing brain plasticity during the remedial instruction of poor readers:

This study used fMRI to longitudinally assess the impact of intensive remedial instruction on cortical activation among 5th grade poor readers during a sentence comprehension task. The children were tested at three time points: prior to remediation, after 100 h of intensive instruction, and 1 year after the instruction had ended. Changes in brain activation were also measured among 5th grade good readers at the same time points for comparison. The central finding was that prior to instruction, the poor readers had significantly less activation than good readers bilaterally in the parietal cortex. Immediately after instruction, poor readers made substantial gains in reading ability, and demonstrated significantly increased activation in the left angular gyrus and the left superior parietal lobule. Activation in these regions continued to increase among poor readers 1 year post-remediation, resulting in a normalization of the activation. These results are interpreted as reflecting changes in the processes involved in word-level and sentence-level assembly. Areas of overactivation were also found among poor readers in the medial frontal cortex, possibly indicating a more effortful and attentionally guided reading strategy.


Brain areas showing greater activation among good readers vs. poor readers at each phase of the study. The same data are presented overlaid on a surface rendering (right column) and overlaid on individual coronal slices (left column) of the normalized Montreal Neurological Institute canonical brain. Yellow ovals encircle parietal activation.

Cat Pols

My apologies, I can't help myself. Another cat video.. click on this link, not the picture below.

Oxytocin attenuates aversive reactions

Here is an interesting report from Dolan's laboratory, showing that oxytocin attenuates our emotional response and amygdala reactivity to faces that we have learned to dislike (enter oxytocin in the 'search MindBlog' box in the left column to note previous postings on oxytocin).

Social relations between humans critically depend on our affective experiences of others. Oxytocin enhances prosocial behavior, but its effect on humans' affective experience of others is not known. We tested whether oxytocin influences affective ratings, and underlying brain activity, of faces that have been aversively conditioned. Using a standard conditioning procedure, we induced differential negative affective ratings in faces exposed to an aversive conditioning compared with nonconditioning manipulation. This differential negative evaluative effect was abolished by treatment with oxytocin, an effect associated with an attenuation of activity in anterior medial temporal and anterior cingulate cortices. In amygdala and fusiform gyrus, this modulation was stronger for faces with direct gaze, relative to averted gaze, consistent with a relative specificity for socially relevant cues. The data suggest that oxytocin modulates the expression of evaluative conditioning for socially relevant faces via influences on amygdala and fusiform gyrus, an effect that may explain its prosocial effects.

Self interest versus the common good in economic policy design.

An essay by Bowles in Science points to a shortcoming in the conventional economic approach to policy design: It overlooks the possibility that economic incentives (i.e. those appealing to self-regarding preferences) may diminish ethical or other reasons for complying with social norms and contributing to the common good. Where this is the case, the kinds of incentives stressed by economists may have counterproductive effects.

Diego Rivera's mural of factory workers at Ford's River Rouge assembly plant (detail). Modern economies require cooperation toward common ends among countless individuals, often occurring as the result of both self-interested and ethical motives. Recent behavioral experiments show that organizational strategies may backfire if they rely solely on explicit economic incentives and seek to limit the options of group members.

One interesting real-life experiment:

In Haifa, at six day care centers, a fine was imposed on parents who were late picking up their children at the end of the day. Parents responded to the fine by doubling the fraction of time they arrived late. When after 12 weeks the fine was revoked, their enhanced tardiness persisted unabated. While other interpretations are possible, the counterproductive imposition of the fines illustrate a kind of negative synergy between economic incentives and moral behavior. The fine seems to have undermined the parents' sense of ethical obligation to avoid inconveniencing the teachers and led them to think of lateness as just another commodity they could purchase.

Here is the abstract of the article:

High-performance organizations and economies work on the basis not only of material interests but also of Adam Smith's "moral sentiments." Well-designed laws and public policies can harness self-interest for the common good. However, incentives that appeal to self-interest may fail when they undermine the moral values that lead people to act altruistically or in other public-spirited ways. Behavioral experiments reviewed here suggest that economic incentives may be counterproductive when they signal that selfishness is an appropriate response; constitute a learning environment through which over time people come to adopt more self-interested motivations; compromise the individual's sense of self-determination and thereby degrade intrinsic motivations; or convey a message of distrust, disrespect, and unfair intent. Many of these unintended effects of incentives occur because people act not only to acquire economic goods and services but also to constitute themselves as dignified, autonomous, and moral individuals. Good organizational and institutional design can channel the material interests for the achievement of social goals while also enhancing the contribution of the moral sentiments to the same ends.

And here is the PDF.

Cute Cat Overload on the Web

Several days ago my daughter sent me this link to a site of humorous cat pictures such as the following.













Now in today's New York Times I see an article by Dan Mitchell on other warm, cuddly, and fuzzy sites. An excerpt:

Meg Frost, a 36-year-old design manager at Apple, started cuteoverload.com three years ago to test Web software. Within months, it became an online institution, drawing about 88,000 unique visitors a day...viewing the site “is like taking a happy pill.”

And in that warm feeling lies the reason for its popularity. Given all the nastiness on the Internet — blog trolls, flame wars, vicious gossip, pornography, snark and spam — what better antidote is there than looking at pictures of tiny ducklings waddling in a line or kittens splayed on their backs, paw pads in the air?

The most famous cute-animal Web sites are presented with a touch of self-mockery. The site I Can Has Cheezburger? (icanhascheezburger.com) features cat pictures with ungrammatical captions, Stuff on My Cat (stuffonmycat.com) displays photos of objects stacked on sleeping cats, and Kittenwars.com pits pairs of cat photos in a cuteness showdown.

Brain Correlates of Borderline Personality Disorder

King-Casas et al. carry out interesting experiments in which they recruited 55 individuals afflicted with borderline personality disorder (BPD) to play a multiround economic exchange game with healthy partners. Imaging experiments were also performed that revealed different patterns of insula activation in BPD subjects. Here is the abstract, followed by a figure from an accompanying review by Meyer-Lindenberg.

To sustain or repair cooperation during a social exchange, adaptive creatures must understand social gestures and the consequences when shared expectations about fair exchange are violated by accident or intent. We recruited 55 individuals afflicted with borderline personality disorder (BPD) to play a multiround economic exchange game with healthy partners. Behaviorally, individuals with BPD showed a profound incapacity to maintain cooperation, and were impaired in their ability to repair broken cooperation on the basis of a quantitative measure of coaxing. Neurally, activity in the anterior insula, a region known to respond to norm violations across affective, interoceptive, economic, and social dimensions, strongly differentiated healthy participants from individuals with BPD. Healthy subjects showed a strong linear relation between anterior insula response and both magnitude of monetary offer received from their partner (input) and the amount of money repaid to their partner (output). In stark contrast, activity in the anterior insula of BPD participants was related only to the magnitude of repayment sent back to their partner (output), not to the magnitude of offers received (input). These neural and behavioral data suggest that norms used in perception of social gestures are pathologically perturbed or missing altogether among individuals with BPD. This game-theoretic approach to psychopathology may open doors to new ways of characterizing and studying a range of mental illnesses.


(Click to enlarge). Activation of the anterior insula is observed during an economic trust game in individuals with borderline personality disorder and healthy controls. Both groups show higher activation in response to stingy repayments they are about to make. However, only players with the disorder have no differential response to low offers from an investor (upper left graph), indicating that they lack the "gut feeling" that the relationship (cooperation) is in jeopardy.

Our expressions of fear and disgust serve specific adaptive purposes

Susskind et al. make some interesting observations that suggest that our facial expressions of fear or disgust are not set by arbitrary social conventions but rather have an evolved Darwinian basis. From Whalen and Kleck's review of this work of this work in the same issue of Nature Neuroscience:

...when subjects posed fearful faces, they were able to detect more flashes of light in the upper extent of their peripheral visual field, they were faster to move their eyes to targets in their visual field and they took in more air through the nose. In contrast, when they posed disgusted expressions, they detected fewer flashes of light in the upper extent of their visual field, they were slower to move their eyes to visual targets and they took in less air through the nose. Thus, the converse movements of the brows, eyelids and nose enacted in the formation of these expressions had opposite effects on sensory intake (see figure). This makes sense when one considers the situations where these expressions are encountered. Fearful expressions are observed at times when you would do well to learn more about your surroundings and disgusted expressions are observed at times when you feel you have learned quite enough.


Note how the various parts of the face move in opposite directions in the two expressions, and therefore have opposite effects on sensory intake.

That eye widening should facilitate environmental monitoring is consistent with other data showing that the amygdala has a unique relationship with fearful facial expressions. Indeed, the amygdala uses the widened eyes in fearful expressions as a proxy for the presence of fearful faces, and lesions of the human amygdala result in an inability to properly scan the eye whites in fearful faces. Further, electrical stimulation of the human amygdala results in eye widening and heightened visual scanning of the environment and produces nonspecific arousal responses such as pupil dilation. Neuroimaging studies have shown that the amygdala is sensitive to the pupil size of others. Taken together, these findings support the hypothesized role of the amygdala in potentiating sensory information processing to facilitate learning about the predi. More generally, these results suggest that your amygdala is sensitive to the very facial responses in others that it controls in you.

If the amygdala has shown an affinity for the facial expression of fear, then the analogous brain region for disgusted expressions would be the insular cortex. Neuroimaging, as well as depth electrode recording studies, show that human insular cortex responds to disgusted faces, and damage to the insula produces deficits in the recognition of disgusted faces11. Furthermore, insular pathology in Huntington's disorder is associated with a decreased disgust response and a similar recognition deficit of disgust. Although it is tempting to divide duties for the amygdala and insular cortex between fear and disgust and to suggest that they represent unique neural substrates for their processing, other work suggests that these reciprocally connected regions will interact along dimensions such as arousal, valence and/or attention, dimensions that cross the stark boundary between these two expression categories.

Mindblog does an experiment with resveratrol, the anti-aging compound.

I have done a number of posts on resveratrol (to have a look at them, enter 'resveratrol' in the search box in the left column). This compound appears to mimic the effects of caloric restriction in some animals, and in some cases extends lifespans. It has effects on enzyme profiles that resemble those caused by exercise. With some hesitation, I decided to do a self-experiment, taking the compound for several weeks to see if I noted any steady state changes in physiology, energy, temperament, etc. and then stopping the supplement to observe whether any changes I noted went away. (Goggling away on the web, you find a large number of sites, having almost the aura of cults, claiming wondrous properties of this new magic molecule.)

If you don't feel like reading through the whole account below, the bottom line is that after noting some positive, but transient, positive changes in energy and temperament, the appearance of arthritic symptoms led me to terminate the self-experiment. The arthritic symptoms then disappeared. (Added note, in response to immediate input from a reader of this post: Resveratrol is an anti-TNF (tumor necrosis factor) agent and in some instances this may trigger autoimmune symptoms.)

The hesitation to start this experiment derived from my experience when I tried this in 2004. Then, as now, I used resveratrol obtained from Now Foods, pills containing 400 mg of a root extract that claims to contain 200 mg resveratrol. After a few weeks I noted that my hands were becoming stiff, finger joints were starting to 'click' , i.e. arthritic symptoms. I freaked out, stopped the resveratrol, and started taking glucose amine, chondroitin sulfate, MSM, Calcium, Magnesium. The arthritis went away over the next week or two, but of course I didn't know whether to attribute that to stopping the resveratrol, starting the latter supplements, or placebo effect.

So, this time I started 200 mg with breakfast, tried to stay very flat and objective in my observations, especially attentive to any negative effects. (I tried in vain to find in the literature, on the web, any reported negative side effects reported by people taking resveratrol.) On day 11, I started another 200 mg with dinner.

On day 13, I decided to write down a number of effects, fairly subtle, but quite clear. (I had been looking mainly for negative symptoms, and so required the following observations to be clear and sustained, noticed as facts, not goals, with changes clearly different from the previous period in a sustained way. My food intake and level of formal exercise (gym) activity had not changed significantly.)

-more constant energy in just moving through a day, from one activity to another… (While running at gym, I didn't begin to slow down after the first mile).
-an absence of mildly negative, curmudgeonly, temperament, the temperament being now more flat to positive.
-more sexual energy (I check the web: resveratrol inhibitis the esterase that breaks down testosterone)
-a bit more spontaneous emotional reactivity, to memories, things in the environment,
-the daily weight range (lowest on waking in the a.m. then plus a few pounds by gym weighing) may have shifted down 1-2 pounds

By day 15 I'm deciding I don’t think the weight range has changed significantly. Further, over a period of just a few days, everything seems to return to where it was, as if physiological and temperamental homeostatic mechanisms had noted a 'perturbation' and so were returning the body to its normal set-points. On day 16 I sign off on thinking that the positive effects reported above are long term. I also realize that hand stiffness has been increasing over the past few days, finger joints have started clicking. (These observations seem to be contrary to several reports that resveratrol inhibits enzymes (COX-1 and COX-2) involved in inflammatory arthritic responses.)

I continue to take the 400 mg of daily resveratrol for two more days, note increasing arthritic symptoms, and discontinue on day. 19. Over the next week, the stiffness and clicking joints disappear, and hand movements become supple again.

So, that is it. Deric's experiment was finished. Don't think I'm going to go there again.

The Mind Does the Tricks for a Magician

Benedict Carey does a fascinating article on how short cuts that our brains make to assemble our perceptions are exploited by magicians. He describes collaboration between magicians and neuroscientists which have generated a paper in Nature Review Neuroscience. One example:

The visual cortex is attentive to sudden changes in the environment, both when something new appears and when something disappears...A sudden disappearance causes an after-discharge: a ghostly image of the object lingers for a moment...This illusion is behind a spectacular trick by the Great Tomsoni. The magician has an assistant appear on stage in a white dress and tells the audience he will magically change the color of her dress to red. He first does this by shining a red light on her, an obvious ploy that he turns into a joke. Then the red light flicks off, the house lights go on and the now the woman is unmistakably dressed in red. The secret: In the split-second after the red light goes off, the red image lingers in the audience’s brains for about 100 milliseconds, covering the image of the woman. It’s just enough time for the woman’s white dress to be stripped away, revealing a red one underneath.

Anticipation of movement suppresses sensory awareness.

Here is an interesting tidbit...Voss et al. show that the mere expectation of moving a part of our body suppresses that body part's openness to sensory input. Here is the abstract:

When a part of the body moves, the sensation evoked by a probe stimulus to that body part is attenuated. Two mechanisms have been proposed to explain this robust and general effect. First, feedforward motor signals may modulate activity evoked by incoming sensory signals. Second, reafferent sensation from body movements may mask the stimulus. Here we delivered probe stimuli to the right index finger just before a cue which instructed subjects to make left or right index finger movements. When left and right cues were equiprobable, we found attenuation for stimuli to the right index finger just before this finger was cued (and subsequently moved). However, there was no attenuation in the right finger just before the left finger was cued. This result suggests that the movement made in response to the cue caused ‘postdictive’ attenuation of a sensation occurring prior to the cue. In a second experiment, the right cue was more frequent than the left. We now found attenuation in the right index finger even when the left finger was cued and moved. This attenuation linked to a movement that was likely but did not in fact occur, suggests a new expectation-based mechanism, distinct from both feedforward motor signals and postdiction. Our results suggest a new mechanism in motor-sensory interactions in which the motor system tunes the sensory inputs based on expectations about future possible actions that may not, in fact, be implemented.

Brooks on status rules and collectivism

Two recent Op-Ed columns by David Brooks are worth a glance. In the first he argues (one has to admit in a rather superficial and facile manner) that the advent of the iPhone signaled the start of a new era in which the means of transmission has replaced the content of culture as the center of historical excitement and as the marker of social status. He cites this as the third of three epochs of intellectual affectation.

The first, lasting from approximately 1400 to 1965, was the great age of snobbery. Cultural artifacts existed in a hierarchy, with opera and fine art at the top, and stripping at the bottom... This code died sometime in the late 1960s and was replaced by the code of the Higher Eclectica. The old hierarchy of the arts was dismissed as hopelessly reactionary...During this period, status rewards went to the ostentatious cultural omnivores — those who could publicly savor an infinite range of historically hegemonized cultural products.

In his third iPhone era:

...prestige has shifted from the producer of art to the aggregator and the appraiser. Inventors, artists and writers come and go, but buzz is forever. Maximum status goes to the Gladwellian heroes who occupy the convergence points of the Internet infosystem — Web sites like Pitchfork for music, Gizmodo for gadgets, Bookforum for ideas, etc.

The second Brooks essay, which probes the different cognitive styles of Eastern and Western socities, is inspired by the opening ceremony of the Beijing Olympics:

The ceremony drew from China’s long history, but surely the most striking features were the images of thousands of Chinese moving as one — drumming as one, dancing as one, sprinting on precise formations without ever stumbling or colliding. We’ve seen displays of mass conformity before, but this was collectivism of the present — a high-tech vision of the harmonious society performed in the context of China’s miraculous growth...If Asia’s success reopens the debate between individualism and collectivism (which seemed closed after the cold war), then it’s unlikely that the forces of individualism will sweep the field or even gain an edge...For one thing, there are relatively few individualistic societies on earth. For another, the essence of a lot of the latest scientific research is that the Western idea of individual choice is an illusion and the Chinese are right to put first emphasis on social contexts.

Different social attachment styles - different brain structures.

Here is an interesting article arguing that three classic prototypes of attachment style (secure, avoidant, anxious) appear to be regulated by two separate affective dimensions centered on ventral striatum and amygdala circuits, respectively. Here is the abstract, to see the fMRI data showing the relevant structures, follow the link to the article.

Adult attachment style refers to individual personality traits that strongly influence emotional bonds and reactions to social partners. Behavioral research has shown that adult attachment style reflects profound differences in sensitivity to social signals of support or conflict, but the neural substrates underlying such differences remain unsettled. Using functional magnetic resonance imaging (fMRI), we examined how the three classic prototypes of attachment style (secure, avoidant, anxious) modulate brain responses to facial expressions conveying either positive or negative feedback about task performance (either supportive or hostile) in a social game context. Activation of striatum and ventral tegmental area was enhanced to positive feedback signaled by a smiling face, but this was reduced in participants with avoidant attachment, indicating relative impassiveness to social reward. Conversely, a left amygdala response was evoked by angry faces associated with negative feedback, and correlated positively with anxious attachment, suggesting an increased sensitivity to social punishment. Secure attachment showed mirror effects in striatum and amygdala, but no other specific correlate. These results reveal a critical role for brain systems implicated in reward and threat processing in the biological underpinnings of adult attachment style, and provide new support to psychological models that have postulated two separate affective dimensions to explain these individual differences, centered on the ventral striatum and amygdala circuits, respectively. These findings also demonstrate that brain responses to face expressions are not driven by facial features alone but determined by the personal significance of expressions in current social context. By linking fundamental psychosocial dimensions of adult attachment with brain function, our results do not only corroborate their biological bases but also help understand their impact on behavior.

The emerging web Leviathan - paranoia over search and content

I thought I would pass on this interesting piece in the New York Times business section on yet more controversy surrounding Google, this time over its emergence as a company that provides not only search results but also original content. I use its two main content subsidiaries: Blogger (to host this blog) and YouTube (the top video site). Now Knol comes along,a potential competitor with Wikipedia, a place where experts can share their knowledge on a variety of topics. The article points out: "Google’s growing reach into the content business could create conflicts similar to those faced by Microsoft in its dual role as a provider of an operating system that others run their software applications on and a maker of applications."

Right hemisphere more involved in self recognition of body parts.

Hemispheric asymmetries in self and other body parts recognition is examined by Frassinetti et al., by comparing how healthy patients, and patients with left and right hemisphere brain damage perform in visual matching experiments involving body parts. Their abstract:

The aim of this study was to investigate whether the recognition of "self body parts" is independent from the recognition of other people's body parts. If this is the case, the ability to recognize "self body parts" should be selectively impaired after lesion involving specific brain areas. To verify this hypothesis, patients with lesion of the right (right brain-damaged [RBD]) or left (left brain-damaged [LBD]) hemisphere and healthy subjects were submitted to a visual matching-to-sample task in two experiments. In the first experiment, stimuli depicted their own body parts or other people's body parts. In the second experiment, stimuli depicted parts of three categories: objects, bodies, and faces. In both experiments, participants were required to decide which of two vertically aligned images (the upper or the lower one) matched the central target stimulus. The results showed that the task indirectly tapped into bodily self-processing mechanisms, in that both LBD patients and normal subjects performed the task better when they visually matched their own, as compared to others', body parts. In contrast, RBD patients did not show such an advantage for self body parts. Moreover, they were more impaired than LBD patients and normal subjects when visually matching their own body parts, whereas this difference was not evident in performing the task with other people's body parts. RBD patients' performance for the other stimulus categories (face, body, object), although worse than LBD patients' and normal subjects' performance, was comparable across categories. These findings suggest that the right hemisphere may be involved in the recognition of self body parts, through a fronto-parietal network.

Circuits that switch fear ON and OFF

Sah and Westbrook write a brief review of work by Herry et al. and Likhtik et al. Here are some mixed and edited clips:

The work pinpoints the neural circuits that mediate the bidirectional transition between a defensive behaviour — fear — and the default exploratory behaviour. These functions are evolutionarily old, and their dysfunction is thought to underlie a host of anxiety disorders in humans, including post-traumatic stress and panic disorder

To study the neural mechanisms that mediate fear responses, fear conditioning is widely used. In a typical procedure, animals are exposed to a normally harmless stimulus (such as a sound or light) before a brief exposure to an aversive stimulus — typically a foot shock. A few such rounds of pairing the harmless (conditioned) stimulus with the aversive (unconditioned) stimulus create an association between them in the animals' minds...It is important to study how fear is first learned. However, the pertinent question for clinicians is how fear can be eliminated or reduced. Extinction of fear occurs when the association between the conditioned and the unconditioned stimuli is broken by repeated presentations of the conditioned stimulus only. But does the association get completely erased from the memory? The answer is no. Although the conditioned stimulus eventually fails to elicit fear responses, much, if not all, of the original learned fear survives extinction. So when the extinguished conditioned stimulus is tested either during, or shortly after, exposure to a dangerous context again, the conditioned fear is renewed spontaneously. Extinction therefore involves new learning, and its activation by situational cues inhibits the expression of fear responses to the conditioned stimulus.

During fear conditioning, convergence of inputs from the conditioned stimulus (CS) and unconditioned stimulus (US) to fear neurons in the basolateral amygdala (BLA) leads to potentiation of the conditioned input and activation by the CS of neurons in the central nucleus (CEA) that initiates physiological and behavioural responses characteristic of fear. b, During extinction, inputs from the medial prefrontal cortex (PFC) activate neurons in the intercalated cell masses (ICMs) — either directly or through activation of extinction neurons in the basolateral amygdala — which then inhibit the activity of fear output neurons in the CEA. c, During fear renewal, inputs from the hippocampus, which evaluates the current context, activate inhibitory interneurons in the basolateral amygdala that silence extinction neurons, thus restoring fear responses.

Noninvasive Brain Stimulation Improves Language Learning

Here are some interesting results from Flöel et al. :

Anodal transcranial direct current stimulation (tDCS) is a reliable technique to improve motor learning. We here wanted to test its potential to enhance associative verbal learning, a skill crucial for both acquiring new languages in healthy individuals and for language reacquisition after stroke-induced aphasia. We applied tDCS (20 min, 1 mA) over the posterior part of the left peri-sylvian area of 19 young right-handed individuals while subjects acquired a miniature lexicon of 30 novel object names. Every subject participated in one session of anodal tDCS, one session of cathodal tDCS, and one sham session in a randomized and double-blinded design with three parallel versions of the miniature lexicon. Outcome measures were learning speed and learning success at the end of each session, and the transfer to the subjects' native language after the respective stimulation. With anodal stimulation, subjects showed faster and better associative learning as compared to sham stimulation. Mood ratings, reaction times, and response styles were comparable between stimulation conditions. Our results demonstrate that anodal tDCS is a promising technique to enhance language learning in healthy adults and may also have the potential to improve language reacquisition after stroke.

Frontal Cortex: unconscious inhibitory control

An interesting study from van Gaal et al. I give the abstract, followed by a figure describing the experimental procedure:

To further our understanding of the function of conscious experience we need to know which cognitive processes require awareness and which do not. Here, we show that an unconscious stimulus can trigger inhibitory control processes, commonly ascribed to conscious control mechanisms. We combined the metacontrast masking paradigm and the Go/No-Go paradigm to study whether unconscious No-Go signals can actively trigger high-level inhibitory control processes, strongly associated with the prefrontal cortex (PFC). Behaviorally, unconscious No-Go signals sometimes triggered response inhibition to the level of complete response termination and yielded a slow down in the speed of responses that were not inhibited. Electroencephalographic recordings showed that unconscious No-Go signals elicit two neural events: (1) an early occipital event and (2) a frontocentral event somewhat later in time. The first neural event represents the visual encoding of the unconscious No-Go stimulus, and is also present in a control experiment where the masked stimulus has no behavioral relevance. The second event is unique to the Go/No-Go experiment, and shows the subsequent implementation of inhibitory control in the PFC. The size of the frontal activity pattern correlated highly with the impact of unconscious No-Go signals on subsequent behavior. We conclude that unconscious stimuli can influence whether a task will be performed or interrupted, and thus exert a form of cognitive control. These findings challenge traditional views concerning the proposed relationship between awareness and cognitive control and stretch the alleged limits and depth of unconscious information processing.

Here is the procedure. SOA is the stimulus-onset asynchrony, the interval between the onsets of the two stimuli. (I wish these people would remind us what these jargon abbreviations mean, so I don't have go look them up to remind myself. )

Stimuli and trial timing of the masked Go/No-Go task and the control experiment. The gray circle and black cross duration was 16.7 ms. Go signal duration was 100 ms. In conscious No-Go trials, the SOA between the No-Go signal and the Go signal was 83 ms. Participants had to respond to the Go signal (black metacontrast mask) but were instructed to withhold their response when a No-Go signal preceded the Go signal. In the masked Go/No-Go task, a gray circle served as a No-Go signal, whereas in the control experiment, the No-Go signal was a black cross. Therefore, the masked gray circle was associated with inhibition in the masked Go/No-Go task and thus served as an unconscious No-Go signal. In the control experiment, the unconscious gray circle was not associated with inhibition (and was task irrelevant) because participants were instructed to inhibit their responses on a black cross. Comparing processing of unconscious gray circles between both experiments enabled us to test whether (1) high-level inhibitory control processes can be triggered unconsciously, (2) unconscious No-Go signals reach prefrontal areas, and (3) task relevance influences the depth of processing of unconscious stimuli.

Music for the week... Ode to Joy

My daughter sent me this gem...

MindBlog at the Chicago Art Institue

Lunch today in the Garden Restaurant at the Art Institute of Chicago, part of my annual summer ritual, which also includes the Halstead Street Days street fair in Boystown. (Click to enlarge picture).

Culture-sensitive neural substrates of human cognition.

Han and Northoff write a perspective piece in which they aim to show how the relatively novel approach of transcultural neuroimaging can bridge the gap between neuroscientific investigations of supposedly culture-invariant neural mechanisms and psychological evidence of culture-sensitive cognition. They collect and summarize a variety of neuroimaging data in summary figures. Below is the abstract, and PDF is here.

Our brains and minds are shaped by our experiences, which mainly occur in the context of the culture in which we develop and live. Although psychologists have provided abundant evidence for diversity of human cognition and behaviour across cultures, the question of whether the neural correlates of human cognition are also culture-dependent is often not considered by neuroscientists. However, recent transcultural neuroimaging studies have demonstrated that one's cultural background can influence the neural activity that underlies both high- and low-level cognitive functions. The findings provide a novel approach by which to distinguish culture-sensitive from culture-invariant neural mechanisms of human cognition.

Behavioral therapy can reverse chronic fatigue syndrome and increase prefrontal volume

Another example of a therapy that induces brain plasticity, this work from de Lange et al. , carried out with women, since chronic fatigue syndrome predominantly affects women. Here is a clip describing the therapy, followed by the abstract of the paper.

During cognitive behavioral therapy (CBT), fatigue-related cognitions were challenged to diminish somatic attributions, to improve sense of control over symptoms and to facilitate behavioral changes. In parallel, a structured physical activity program was implemented. Furthermore, a work rehabilitation schedule was drawn up in order to realize a gradual work reentry. Final sessions of CBT dealt with relapse prevention and further improvement of self-control.

Chronic fatigue syndrome (CFS) is a disabling disorder, characterized by persistent or relapsing fatigue. Recent studies have detected a decrease in cortical grey matter volume in patients with CFS, but it is unclear whether this cerebral atrophy constitutes a cause or a consequence of the disease. Cognitive behavioural therapy (CBT) is an effective behavioural intervention for CFS, which combines a rehabilitative approach of a graded increase in physical activity with a psychological approach that addresses thoughts and beliefs about CFS which may impair recovery. Here, we test the hypothesis that cerebral atrophy may be a reversible state that can ameliorate with successful CBT. We have quantified cerebral structural changes in 22 CFS patients that underwent CBT and 22 healthy control participants. At baseline, CFS patients had significantly lower grey matter volume than healthy control participants. CBT intervention led to a significant improvement in health status, physical activity and cognitive performance. Crucially, CFS patients showed a significant increase in grey matter volume, localized in the lateral prefrontal cortex. This change in cerebral volume was related to improvements in cognitive speed in the CFS patients. Our findings indicate that the cerebral atrophy associated with CFS is partially reversed after effective CBT. This result provides an example of macroscopic cortical plasticity in the adult human brain, demonstrating a surprisingly dynamic relation between behavioural state and cerebral anatomy. Furthermore, our results reveal a possible neurobiological substrate of psychotherapeutic treatment.

Mental imagergy induces cortical reorganization that reduces phantom limb pain

The journal Brain offers an interesting open access article by MacIver et al. on the use of mental imagery to reduce phantom limb pain. They used a mindfulness-based ‘body-scan’ meditation technique as a means of achieving a relaxed state, based on a pain management technique developed by Kabat-Zinn et al. This remarkably simple technique of imagining movement and sensation in the missing limb resulted in significant pain relief. All subjects found learning the body scan useful as a means of relaxation, regardless of whether their pain lessened, and they all felt that the body scan was a useful facilitator to imagining the return of the phantom limb. I give the abstract here, with apologies for not taking the time to translate it into more friendly prose.

Using functional MRI (fMRI) we investigated 13 upper limb amputees with phantom limb pain (PLP) during hand and lip movement, before and after intensive 6-week training in mental imagery. Prior to training, activation elicited during lip purse showed evidence of cortical reorganization of motor (M1) and somatosensory (S1) cortices, expanding from lip area to hand area, which correlated with pain scores. In addition, during imagined movement of the phantom hand, and executed movement of the intact hand, group maps demonstrated activation not only in bilateral M1 and S1 hand area, but also lip area, showing a two-way process of reorganization. In healthy participants, activation during lip purse and imagined and executed movement of the non-dominant hand was confined to the respective cortical representation areas only. Following training, patients reported a significant reduction in intensity and unpleasantness of constant pain and exacerbations, with a corresponding elimination of cortical reorganization. Post hoc analyses showed that intensity of constant pain, but not exacerbations, correlated with reduction in cortical reorganization. The results of this study add to our current understanding of the pathophysiology of PLP, underlining the reversibility of neuroplastic changes in this patient population while offering a novel, simple method of pain relief.

Sexual orientation - basis in brain structure and function

Swaab offers a useful brief review of this topic (PDF here) with a complete list of references.

Genetics of political behaviors - molecular level

I wanted to bring into a separate post the comment by James Fowler on the post below mentioning his work. "We do have some papers that go to the molecular level, associating drd2, drd4, maoa, and 5htt with various political behaviors. One of these papers has just been published in Journal of Politics, and all of these papers are all available at my website
http://jhfowler.ucsd.edu."

Your nose, and your bored brain...

From today's Science NYTimes: An article by Natalie Angier on the emotional clout of smells and the curious fact that smell cues most frequently evoke thoughts of early childhood, under the age of 10 (this certainly has been my experience.) Also, an article by Benedict Carey on the creative aspects of boredome.

A new perspective on the genetic basis of brain diseases

An article by Nicholas Wade notes the emergence of a new view on the genetic basis of brain diseases like schizophrenia (see also article by Sands in Nature). There has been a presumption that we looked hard enough, we would find an ensemble of genes whose mutations typically correlated with a disease. The search for common variants in schizophrenia has largely drawn a blank, suggesting that natural selection has done its job in keeping them at bay (after all, reproductive success is compromised in schizophrenics). A view is emerging that the genetic component of the disease may be due to a large number of variants, each of which is very rare (mainly deletions of DNA segments), rather than to a handful of common variants. According to this new idea, schizophrenia continues to appear because it is driven by a spate of new mutations that occur all the time in the population. The new landscape might complicate development of genetic diagnostics for schizophrenia, but not necessarily of therapies based on understanding the underlying mechanisms of the disease.

Gender differences in math performance...

... don't exist for children in grades 2 to 11, according according to a massive statistical analysis carried out by Hyde et al. on data provided through school reporting on the No Child Left Behind federal program (PDF here) - although there is slightly more male variability in scores.

The theologians, the neurologists, and God

Here is the PDF of a review by Alasdair Coles in a recent issue of Brain of a series of recent books that evaluate contributions of neurobiology to the understanding of the relationships between brain, psyche and God. He reviews the history of such efforts starting with Pascal, William James, and others.

Mendelssohn, conclusion

Here is the posting of the final piece done at the house concert at Twin Valley on 6/29/08 the final movement, allegro appasionata, of Mendelssohn's 2nd piano trio. A notable feature of this finale is its inclusion of the melody of a chorale taken from the sixteenth-century Genevan psalter ''Vor deinen Thron tret ich hiermit.'

Lifespan Mental Activity Predicts Diminished Rate of Hippocampal Atrophy

Valenzuela et al. offer further confirmation of the 'use it or lose it' perspective by showing that lifetime mental activity correlates with a diminished rate of hippocampal atrophy with aging. They suggest that neuroprotection in medial temporal lobe may be one mechanism underlying the link between mental activity and lower rates of dementia observed in population-based studies.

We learn abstract categories unconsciously.

Brady and Oliva report interesting experiments in Psychological Science. Below I pass on their abstract, and also their presentation of the first experiment mentioned:

Recent work has shown that observers can parse streams of syllables, tones, or visual shapes and learn statistical regularities in them without conscious intent (e.g., learn that A is always followed by B). Here, we demonstrate that these statistical-learning mechanisms can operate at an abstract, conceptual level. In Experiments 1 and 2, observers incidentally learned which semantic categories of natural scenes covaried (e.g., kitchen scenes were always followed by forest scenes). Stimuli: In Experiments 3 and 4, category learning with images of scenes transferred to words that represented the categories. In each experiment, the category of the scenes was irrelevant to the task. Together, these results suggest that statistical-learning mechanisms can operate at a categorical level, enabling generalization of learned regularities using existing conceptual knowledge. Such mechanisms may guide learning in domains as disparate as the acquisition of causal knowledge and the development of cognitive maps from environmental exploration.

From their description of the first experiment:

Stimuli: Twelve scene categories were used (see figure): bathroom, bedroom, bridge, building, coast, field, forest, kitchen, living room, mountain, street, and waterfall.


Each category contained 120 different full-color images. For each observer, 1 picture was drawn from each of the 12 categories at random, resulting in a set of 12 different images...Each of the 12 selected images was randomly assigned a position in one of four triplets (e.g., ABC)—sequences of three images that always appeared in the same order. Then a sequence of images was generated by randomly interleaving 75 repetitions of each triplet, with the constraints that the same triplet could never appear twice in a row and the same set of two triplets could never appear twice in a row (e.g., ABCGHIABCGHI was disallowed). In addition, 100 repeat images were inserted into the stream such that sometimes either the first or third image in a triplet repeated immediately (e.g., ABCCGHI or ABCGGHI). Allowing only the first or third image in a triplet to repeat served to keep the triplet structure intact, yet prevented the repeat images from being informative for delineating triplets from one another.

Procedure: Observers watched a 20-min sequence of 1,000 images, presented one at a time for 300 ms each with a 700-ms interstimulus interval (ISI). During this sequence, the task was to detect back-to-back repeats of the same image and to indicate repeats as quickly as possible by hitting the space bar. This cover task was intended to help prevent observers from becoming explicitly aware of the structure in the stream (Turk-Browne et al., 2005), and also avoided having observers simply view the stream passively (which would make it unclear what they were processing). Note that they were never informed that there was any structure in the stream of images...Following this study period, observers were asked if they had recognized any structure in the stream and then were given a surprise forced-choice familiarity test. On each test trial, observers viewed two 3-image test sequences, presented sequentially at the center of the screen with the same ISI as during the study phase and segmented from each other by an additional 1,000-ms pause. One of these test sequences was always a triplet of images that had been seen in the stream (e.g., ABC), and another was a foil constructed from images from three different triplets (e.g., AEI). After the presentation of the two test sequences, observers were told to press either the "1" or the "2" key to indicate whether the first or second test sequence seemed more familiar from the initial study period. Each of the four triplets was tested eight times, paired twice with each of four different foil sequences (AEI, DHL, GKC, JBF), for a total of 32 test trials. Observers' ability to discriminate triplet sequences from foil sequences was used as a measure of statistical learning.

Results and Discussion: All 10 of the observers completed the repeat-detection task during the study period with few errors, detecting an average of 91% of the repetitions (SD= 5%) and committing between one and five false alarms. These results demonstrate that observers were attending to the sequence of images. However, when asked, no observers reported explicitly noticing that the study stream had any structure.1 Nonetheless, performance on the familiarity test indicated very robust statistical learning, with triplets being successfully discriminated from foils (86.6% of the test sequences chosen were triplets, and 13.4% were foils), t(9) = 8.72, p= .00001.

These results extend previous demonstrations of visual statistical learning in two ways. First, they demonstrate visual statistical learning for scene stimuli, which are more complicated and information rich than the stimuli for which statistical learning has been demonstrated previously. Second, choosing the correct triplets at test in this experiment required not just forming episodic associations between the correct pictures, but also overcoming prior knowledge about how the scenes represented are associated in the world (e.g., bridges are rarely associated with living rooms).

In this experiment, learning likely occurred at the image level, because identical stimuli were repeated throughout the learning and test phases (and statistical learning has been previously demonstrated for shape and color.

To examine the role of category-level semantics in statistical learning, the authors then moved on to experiments in which the same string of images was never presented twice, but a pattern occurred at the categorical level.

Would I pull that switch?

I recommend this NYTimes piece by Benedict Carey on recent experiments that give more nuance to the classic Stanley Milgram obedience studies of the early 1960s,

...that together form one of the darkest mirrors the field has held up to the human face. In a series of about 20 experiments, hundreds of decent, well-intentioned people agreed to deliver what appeared to be increasingly painful electric shocks to another person, as part of what they thought was a learning experiment. The “learner” was in fact an actor, usually seated out of sight in an adjacent room, pretending to be zapped.

The more recent work looks at conditions under which which participants were most likely to disobey the experimenter and quit delivering shocks. The participants' perception of the human rights of the learner as well as whether they felt themselves or the experiments actually responsible for delivering the shocks influenced the threshold beyond which they would no longer obey the experimenter.