Predictability determines whether our attention fades away.

A universal feature of our sensory systems (vision, audition, touch, etc.) is that they adapt, or habituate, to a repeated stimulus - their reporting grows weaker. The common view is that this decrement in response is due largely to automatic processes in sensory neurons. Doing fMRI measurements of cortical responses to photographs of sequentially displayed faces, Summerfield et al. find evidence of a further 'top-down' mechanism for repetition suppression:

By manipulating the likelihood of stimulus repetition, we found that repetition suppression in the human brain was reduced when stimulus repetitions were improbable (and thus, unexpected). Our data suggest that repetition suppression reflects a relative reduction in top-down perceptual 'prediction error' when processing an expected, compared with an unexpected, stimulus.

Vasopressin receptor genes of philandering men

Wow, this little item went from online publications by Proc. Nat. Acad. Sci. yesterday straight to the NBC evening news I watched last night. We were bound eventually to find out that what's true for randy male prairie voles is also true for human males. Walum et al:

Pair-bonding has been suggested to be a critical factor in the evolutionary development of the social brain. The brain neuropeptide arginine vasopressin (AVP) exerts an important influence on pair-bonding behavior in voles. There is a strong association between a polymorphic repeat sequence in the 5′ flanking region of the gene (avpr1a) encoding one of the AVP receptor subtypes (V1aR), and proneness for monogamous behavior in males of this species. It is not yet known whether similar mechanisms are important also for human pair-bonding. Here, we report an association between one of the human AVPR1A repeat polymorphisms (RS3) and traits reflecting pair-bonding behavior in men, including partner bonding, perceived marital problems, and marital status, and show that the RS3 genotype of the males also affects marital quality as perceived by their spouses. These results suggest an association between a single gene and pair-bonding behavior in humans, and indicate that the well characterized influence of AVP on pair-bonding in voles may be of relevance also for humans.

We can use our visual cortex for touch

Merabet et al. perform the fascinating experiment of simply blindfolding normal subject for five days, during which intensive tactile training is carried out that improves the subjects' ability to read Braille characters. fMRI measurements reveal an increase in visual cortex responses to tactile stimulation during this period, suggesting that a non-visual input to the visual cortex is being unmasked.

...This increase in signal was no longer present 24 hours after blindfold removal. Finally, reversible disruption of occipital cortex function on the fifth day (by repetitive transcranial magnetic stimulation; rTMS) impaired Braille character recognition ability in the blindfold group but not in non-blindfolded controls. This disruptive effect was no longer evident once the blindfold had been removed for 24 hours.

Overall, our findings suggest that sudden and complete visual deprivation in normally sighted individuals can lead to profound, but rapidly reversible, neuroplastic changes by which the occipital cortex becomes engaged in processing of non-visual information. The speed and dynamic nature of the observed changes suggests that normally inhibited or masked functions in the sighted are revealed by visual loss. The unmasking of pre-existing connections and shifts in connectivity represent rapid, early plastic changes, which presumably can lead, if sustained and reinforced, to slower developing, but more permanent structural changes, such as the establishment of new neural connections in the blind.

Updating our memory requires its original context.

Here is some fascinating work by Hupbach et. al. A clip from a Science Magazine summary:

Recent research has shown that reactivating apparently stable memories can render them fragile and open to modification and to another round of stabilization in a process called reconsolidation. Hupbach et al. explored the conditions leading to the updating of episodic memory. They found that memory plasticity at reactivation provides a mechanism for updating memories, and that the latter are determined by the spatial context; that is, the "where" of episodic memory. Only when the memory was reactivated in the same context as when it was learned could new learning be incorporated into the existing store of knowledge; if reactivated in a new context, no updating occurred.

The abstract of the work:

Understanding the dynamics of memory change is one of the current challenges facing cognitive neuroscience. Recent animal work on memory reconsolidation shows that memories can be altered long after acquisition. When reactivated, memories can be modified and require a restabilization (reconsolidation) process. We recently extended this finding to human episodic memory by showing that memory reactivation mediates the incorporation of new information into existing memory. Here we show that the spatial context plays a unique role for this type of memory updating: Being in the same spatial context during original and new learning is both necessary and sufficient for the incorporation of new information into existing episodic memories. Memories are automatically reactivated when subjects return to an original learning context, where updating by incorporating new contents can occur. However, when in a novel context, updating of existing memories does not occur, and a new episodic memory is created instead.

The neural correlates of desire...

Kawabata and Zeki show that categorizing any stimulus according to its desirability activates three different brain areas: the superior orbito-frontal, the mid-cingulate, and the anterior cingulate cortices. The article has the usual pretty fMRI pictures. (Now - if we could just get a fix on the areas active in desire's satiation and avoid all the fuss of real life by just stimulating them directly!)

Predicting the choices of undecided voters - the unseen mind

Not to much of a surprise, but voters who declare themselves to be undecided may be fooling themselves, and are actually unconsciously biased towards one of the choices presented. As Wilson and Bar-Anan point out in their review of the work of Galdi et al.

Social psychologists have discovered an adaptive unconscious that allows people to size up the world extremely quickly, make decisions, and set goals--all while their conscious minds are otherwise occupied. The human mind operates largely out of view of its owners, possibly because that's the way it evolved to work initially, and because that's the way it works best, under many circumstances. Without such an efficient, powerful, and fast means of understanding and acting on the world, it would be difficult to survive. We would be stuck pondering every little decision, such as whether to put our left or right foot forward first, as the world sped by (2-7). But as a result, we are often strangers to ourselves, unable to observe directly the workings of our own minds.

Confabulation. As in this drawing by Saul Steinberg, people construct images of themselves. In real life, people do not realize that their self-knowledge is a construction, and fail to recognize that they possess a vast adaptive unconscious that operates out of their conscious awareness.

Here is the abstract of Galdi et al. that supports this picture using computer-based measures that assess implicit attitudes and traits:

Common wisdom holds that choice decisions are based on conscious deliberations of the available information about choice options. On the basis of recent insights about unconscious influences on information processing, we tested whether automatic mental associations of undecided individuals bias future choices in a manner such that these choices reflect the evaluations implied by earlier automatic associations. With the use of a computer-based, speeded categorization task to assess automatic mental associations (i.e., associations that are activated unintentionally, difficult to control, and not necessarily endorsed at a conscious level) and self-report measures to assess consciously endorsed beliefs and choice preferences, automatic associations of undecided participants predicted changes in consciously reported beliefs and future choices over a period of 1 week. Conversely, for decided participants, consciously reported beliefs predicted changes in automatic associations and future choices over the same period. These results indicate that decision-makers sometimes have already made up their mind at an unconscious level, even when they consciously indicate that they are still undecided.

A 'training of the conscious by the unconscious' is suggested by the observation that the conscious beliefs of the decided voters, which, at the first question period, showed no correlation with their automatic or implicit preferences, did, in fact, predict their implicit preferences during the second session. This suggests that the interaction between unconscious and conscious cognition is a two-way street.

Update on my "Biology of Mind" book - an ebook version

I had an email exchange yesterday with Michiel, in the Netherlands, who has now formatted the web version of my Biology of Mind book as a Sony-formatted file and also as raw HTML for conversion to whatever format you prefer. These are now posted at the mobileread site. (Here is the HTML version which you can simply download, un-zip, and drag into your web browser's window.) In the process, Michiel cleaned up some background noise in the illustrations, and I have placed his improved figures in my website's version of the book. I am most grateful to him for what was a rather major effort.

Ability to use symbols appeared 35 million years ago?

Humans are sometimes said to be distinguished as "The Symbolic Species." A Research Highlights note in Nature point to the work of Addessi et al., who show that capuchin monkeys, who diverged from the human lineage ~35 million years ago, can be trained to use and assign value to tokens (symbols) for different items of food.

...Elsa Addessi of the CNR, Italy's national research council, and her colleagues trained five monkeys to associate a particular token — such as a green chip, black plastic tube or a brass hook — with one of three specific types of food. They then gave the monkeys a series of choices, each time between different amounts of two food items or between two types of token...The value the monkeys assigned to a token was very similar to the value they gave to the food it represented, which suggests that the animals weighed up both real and symbolic options in an equivalent manner.

Cultural evolution in the laboratory

Kirby et al. offer experimental validation for the idea that cultural transmission can lead to the appearance of design without a designer. The abstract is below, and the experimental design best appreciated by examining the paper here:

We introduce an experimental paradigm for studying the cumulative cultural evolution of language. In doing so we provide the first experimental validation for the idea that cultural transmission can lead to the appearance of design without a designer. Our experiments involve the iterated learning of artificial languages by human participants. We show that languages transmitted culturally evolve in such a way as to maximize their own transmissibility: over time, the languages in our experiments become easier to learn and increasingly structured. Furthermore, this structure emerges purely as a consequence of the transmission of language over generations, without any intentional design on the part of individual language learners. Previous computational and mathematical models suggest that iterated learning provides an explanation for the structure of human language and link particular aspects of linguistic structure with particular constraints acting on language during its transmission. The experimental work presented here shows that the predictions of these models, and models of cultural evolution more generally, can be tested in the laboratory.

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.

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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.