The hidden structure of over-imitation

Human children, unlike chimpanzees, will copy unnecessary or arbitrary parts of an action sequence they observe in adults, Lyons et al. term this process overimitation and suggest in an open access article with the title of this post that it reveals a hidden structure behind how children learn to attribute causality. Here is their abstract, and a graphic showing one of the three puzzle boxes used in the experiements:

Young children are surprisingly judicious imitators, but there are also times when their reproduction of others' actions appears strikingly illogical. For example, children who observe an adult inefficiently operating a novel object frequently engage in what we term overimitation, persistently reproducing the adult's unnecessary actions. Although children readily overimitate irrelevant actions that even chimpanzees ignore, this curious effect has previously attracted little interest; it has been assumed that children overimitate not for theoretically significant reasons, but rather as a purely social exercise. In this paper, however, we challenge this view, presenting evidence that overimitation reflects a more fundamental cognitive process. We show that children who observe an adult intentionally manipulating a novel object have a strong tendency to encode all of the adult's actions as causally meaningful, implicitly revising their causal understanding of the object accordingly. This automatic causal encoding process allows children to rapidly calibrate their causal beliefs about even the most opaque physical systems, but it also carries a cost. When some of the adult's purposeful actions are unnecessary—even transparently so—children are highly prone to mis-encoding them as causally significant. The resulting distortions in children's causal beliefs are the true cause of overimitation, a fact that makes the effect remarkably resistant to extinction. Despite countervailing task demands, time pressure, and even direct warnings, children are frequently unable to avoid reproducing the adult's irrelevant actions because they have already incorporated them into their representation of the target object's causal structure.

Vegansexuality

Jeff Stryker gives us more from the fringe (Dec. 9 NY Times Magazine):

Forget homo-, bi- or even metro-: the latest prefix in sexuality is vegan-, as in “vegansexual.” In a study released in May, Annie Potts, a researcher at the University of Canterbury and a director of the New Zealand Centre for Human-Animal Studies, surveyed 157 vegans and vegetarians (120 of them women) on the topic of cruelty-free living. The questions ranged from attitudes about eating meat to keeping pets to wearing possum fur to, yes, “cruelty-free sex” — that is, “rejecting meat eaters as intimate partners.”

Some of the survey respondents volunteered their reluctance to kiss meat eaters. “I couldn’t think of kissing lips that allow dead animal pieces to pass between them,” a 49-year-old vegan woman from Auckland said. For some, the resistance is the squeamishness factor. “Nonvegetarian bodies smell different to me,” a 41-year-old Christchurch vegan woman said. “They are, after all, literally sustained through carcasses — the murdered flesh of others.” For some, it is a question of finding a like-minded life partner. An Auckland ovo-vegetarian had tried a relationship with a carnivore, but reported that despite the sexual attraction, the gulf in “shared values and moral codes” was just too wide.

Potts, who coined the term vegansexuality, says the “negative response of omnivores” to her study has surprised her. Even some fellow animal lovers question the wisdom of vegansexuality. A blog for People for the Ethical Treatment of Animals noted that sleeping with only fellow vegans means forgoing the opportunity to turn carnivores into vegans by the most powerful recruiting tool available — sex.

PETA’s founder and president, Ingrid Newkirk, agrees that vegans smell fresher. (“There’s science to prove it,” she says.) But Newkirk is all about the recruiting, even if it means one convert at a time. “When my staff members come to me and say: ‘Guess what? My boyfriend, now he’s a vegan,’ I say, half-jokingly: ‘Well, it is time to ditch him and get another. You’ve done your work; move on.’ ”

Selling brain science... Neurorealism

Matthew Hutson makes some good points in his brief comments on all those pretty brain imaging graphics you see in this MindBlog as well the daily press:

You’ve seen the headlines: This Is Your Brain on Politics. Or God. Or Super Bowl Ads. And they’re always accompanied by pictures of brains dotted with seemingly significant splotches of color. Now some scientists have seen enough. We’re like moths, they say, lured by the flickering lights of neuroimaging — and uncritically accepting of conclusions drawn from it.

A paper published online in September by the journal Cognition shows that assertions about psychology — even implausible ones like “watching television improved math skills” — seem much more believable to laypeople when accompanied by images from brain scans. And a paper accepted for publication by The Journal of Cognitive Neuroscience demonstrates that adding even an extraneous reference to the brain to a bad explanation of human behavior makes the explanation seem much more satisfying to nonexperts.

Eric Racine, a bioethicist at the Montreal Clinical Research Institute, coined the word neurorealism to describe this form of credulousness. In an article called “fMRI in the Public Eye,” he and two colleagues cited a Boston Globe article about how high-fat foods activate reward centers in the brain. The Globe headline: “Fat Really Does Bring Pleasure.” Couldn’t we have proved that with a slice of pie and a piece of paper with a check box on it?

The way conclusions from cognitive neuroscience studies are reported in the popular press, “they don’t necessarily tell us anything we couldn’t have found out without using a brain scanner,” says Deena Weisberg, an author of the Journal of Cognitive Neuroscience paper. “It just looks more believable now that we have the pretty pictures.”

Racine says he is particularly troubled by the thought of crude or unscrupulous applications of this young science to the diagnosis of psychiatric conditions, the evaluation of educational programs and the assessment of defendants in criminal trials. Drawing inferences from the data requires several degrees of analysis and interpretation, he says, and treating neuroimaging as a mind-reading technique “would be adding extra scientific credibility that is not necessarily warranted.”

Race and IQ - a few crisp facts

The debate over race and IQ seems endless and mind-numbing, usually generating more heat than light. A recent Op-Ed piece by Richard Nisbett, brief and to the point, collects several facts:

About 25 percent of the genes in the American black population are European, meaning that the genes of any individual can range from 100 percent African to mostly European. If European intelligence genes are superior, then blacks who have relatively more European genes ought to have higher I.Q.’s than those who have more African genes. But it turns out that skin color and “negroidness” of features — both measures of the degree of a black person’s European ancestry — are only weakly associated with I.Q. (even though we might well expect a moderately high association due to the social advantages of such features).

During World War II, both black and white American soldiers fathered children with German women. Thus some of these children had 100 percent European heritage and some had substantial African heritage. Tested in later childhood, the German children of the white fathers were found to have an average I.Q. of 97, and those of the black fathers had an average of 96.5, a trivial difference.

If European genes conferred an advantage, we would expect that the smartest blacks would have substantial European heritage. But when a group of investigators sought out the very brightest black children in the Chicago school system and asked them about the race of their parents and grandparents, these children were found to have no greater degree of European ancestry than blacks in the population at large.

.. a superior adoption study...looked at black and mixed-race children adopted by middle-class families, either black or white, and found no difference in I.Q. between the black and mixed-race children....children adopted by white families had I.Q.’s 13 points higher than those of children adopted by black families. The environments that even middle-class black children grow up in are not as favorable for the development of I.Q. as those of middle-class whites.

James Flynn, a philosopher and I.Q. researcher in New Zealand, has established that in the Western world as a whole, I.Q. increased markedly from 1947 to 2002. In the United States alone, it went up by 18 points. Our genes could not have changed enough over such a brief period to account for the shift; it must have been the result of powerful social factors. And if such factors could produce changes over time for the population as a whole, they could also produce big differences between subpopulations at any given time.

...interventions at every age from infancy to college can reduce racial gaps in both I.Q. and academic achievement, sometimes by substantial amounts in surprisingly little time. This mutability is further evidence that the I.Q. difference has environmental, not genetic, causes.

Video of independent leg movement controllers

Here, as a companion to my Sept. 20 post "Walking the walk" is a video illustrating the independent controllers of our right and left legs during walking.

The God Effect

Here I pass on another bit, by Marina Krakovsky, in the NY Times Magazine's Dec. 9 "Ideas" issue. She summarizes work by Canadian psychologists Shariff and Norenzayan published in Psychological Science:

Some anthropologists argue that the idea of God first arose in larger societies, for the purpose of curbing selfishness and promoting cooperation. Outside a tightly knit group, the reasoning goes, nobody can keep an eye on everyone’s behavior, so these cultures invented a supernatural agent who could. But does thinking of an omniscient God actually promote altruism? The University of British Columbia psychologist Ara Norenzayan wanted to find out.

In a pair of studies published in Psychological Science, Norenzayan and his student Azim F. Shariff had participants play the so-called “dictator game,” a common way of measuring generosity toward strangers. The game is simple: you’re offered 10 $1 coins and told to take as many as you want and leave the rest for the player in the other room (who is, unbeknown to you, a research confederate). The fair split, of course, is 50-50, but most anonymous “dictators” play selfishly, leaving little or nothing for the other player.

In the control group of Norenzayan’s study, the vast majority of participants kept everything or nearly everything — whether or not they said they were religious. “Religious leaders always complain that people don’t internalize religion, and they’re right,” Norenzayan observes.

But is there a way to induce generosity? In the experimental condition, the researchers prompted thoughts of God using a well-established “priming” technique: participants, who again included both theists and atheists, first had to unscramble sentences containing words such as God, divine and sacred. That way, going into the dictator game, players had God on their minds without being consciously aware of it. Sure enough, the “God prime” worked like a charm, leading to fairer splits. Without the God prime, only 12 percent of the participants split the money evenly, but when primed with the religious words, 52 percent did.

When news of these findings made headlines, some atheists were appalled by the implication that altruism depends heavily on religion. Apparently, they hadn’t heard the whole story. In a second study, the researchers had participants unscramble sentences containing words like civic, contract and police — meant to evoke secular moral institutions. This prime also increased generosity. And unlike the religious prime, it did so consistently for both believers and nonbelievers. Until he conducts further research, Norenzayan can only speculate about the significance: “We need that common denominator that works for everyone.

A Mea Culpa - Pinker and his critics

I think in general that Steven Pinker goes way overboard on the nativist angle, and so recently approvingly passed on this Churchland review in the Nov. 1 issue of Nature critical of Pinker's new book, "The Language of Thought." - I hadn't actually read the book. These retorts by Marc Hauser and Pinker himself in the Dec. 6 issue make me realize that I should have. I have zapped my original post, and I'm now going to read the book......(one thing about doing a blog is that you read fewer good long books). I admit to a residual grumpyness about Pinker (a brilliant man) from his visit to Wisconsin a number of years ago as a featured speaker. He was dragged through the usual torture of serial 30 minute interviews with local "prominent persons" (I was the Zoology Chair at that time), and during our conversation I found him to be quite remote. At his talk he read from a typescript - word for word - a lecture that I had already heard twice before.

Seasonal Affective Disorder - an evolutionary relic?

Friedman offers a succinct summary of information of seasonal affective disorder (SAD), with some interesting facts.

Epidemiological studies estimate that its prevalence in the adult population ranges from 1.4 percent (Florida) to 9.7 percent (New Hampshire).

In one study, patients with SAD

...had a longer duration of nocturnal melatonin secretion in the winter than in the summer, just as with other mammals with seasonal behavior.Why did the normal patients show no seasonal change in melatonin secretion? One possibility is exposure to industrial light, which can suppress melatonin.
...The effects of light therapy are fast, usually four to seven days, compared with antidepressants, which can take four to six weeks to work.
...People are most responsive to light therapy early in the morning, just when melatonin secretion begins to wane, about eight to nine hours after the nighttime surge begins...How can the average person figure that out without a blood test? By a simple questionnaire that assesses “morningness” or “eveningness” and that strongly correlates with plasma melatonin levels. The nonprofit Center for Environmental Therapeutics has a questionnaire on its Web site (www.cet.org).

"Mental reserves" as antidote to Alzheimer's disease

A fascinating aspect of various kinds of debilitation (back pain, heart attacks, dementia) is that degenerative changes in anatomy commonly associated with them (disk and vertebral degeneration, cardiac vessel blockage, brain lesion and beta-amyloid plaques-shown in figure) are often observed on autopsy in physically and mental robust people, who have shown no symptoms of debilitation. What is different about them? Apparently their bodies were able to do a more effective 'work around' or compensation for the damage. A relevant article by Jane Brody in the December 11 New York Times deals with evidence that cognitive reserves, the brain’s ability to develop and maintain extra neurons and connections between them may later in life help compensate for the rise in dementia-related brain pathology that accompanies normal aging. Some edited clips:

Cognitive reserve is greater in people who complete higher levels of education. The more intellectual challenges to the brain early in life, the more neurons and connections the brain is likely to develop and perhaps maintain into later years... brain stimulation does not have to stop with the diploma. Better-educated people may go on to choose more intellectually demanding occupations and pursue brain-stimulating hobbies, resulting in a form of lifelong learning...novelty is crucial to providing stimulation for the aging brain...as with muscles, it’s “use it or lose it.” The brain requires continued stresses to maintain or enhance its strength...In 2001, ... a long-term study of cognitively healthy elderly New Yorkers....found, on average, those who pursued the most leisure activities of an intellectual or social nature had a 38 percent lower risk of developing dementia. The more activities, the lower the risk...the most direct route to a fit mind is through a fit body...physical exercise “improves what scientists call ‘executive function,’ the set of abilities that allows you to select behavior that’s appropriate to the situation, inhibit inappropriate behavior and focus on the job at hand in spite of distractions. Executive function includes basic functions like processing speed, response speed and working memory.

This point about exercise and executive function was the subject of my Nov. 15 post.

Ambiguity Promotes Liking

For the seventh consecutive December, the New York Times magazine (Dec. 9 issue) has looked back on the passing year through the special lens of 'ideas'. Here is one of their brief essays, and I will pass on a few more in subsequent posts:

Ambiguity Promotes Liking

By MARINA KRAKOVSKY

Is it true that familiarity breeds contempt? A psychology study published this year concludes that the answer is yes. It seems we are inclined to interpret ambiguous information about someone optimistically, assuming we will get along. We are usually let down, however, when we learn more.

A team of researchers, led by Michael I. Norton of Harvard Business School, looked at online daters’ opinions of people they were about to meet for the first time and compared those ratings with another group’s post-date impressions. Before the date, based on what little information the daters saw online, most participants rated their prospective dates between a 6 and a 10 on a 10-point scale, with nobody giving a score below a 3. But post-date scores were lower, on average, and lots of people deemed their date a total dud.

Why? For starters, initial information is open to interpretation. “And people are so motivated to find somebody they like that they read things into the profiles,” Norton says. If a man writes that he likes the outdoors, his would-be mate imagines her perfect skiing companion, but when she learns more, she discovers “the outdoors” refers to nude beaches. And “once you see one dissimilarity, everything you learn afterward gets colored by that,” Norton says.

The letdown from getting more information isn’t true just for romance. In one experiment, the researchers showed college students different numbers of randomly selected traits and asked them to rate how much they’d like the person described. For the most part, the more traits participants saw, the less they said they would like the other person. But another group of students had overwhelmingly said they would like people more after learning more about them.

We make this mistake, the researchers say, largely because we can all recall cases of more knowledge leading to more liking. “You forget the people in your third-grade class you didn’t like; you remember the people you’re still friends with,” Norton explains.

Most popular consciousness articles for November

From the monthly report of downloads from the eprint archives of the Assoc. for the Study of Consciousness:

1. Sagiv, Noam and Ward, Jamie (2006) Crossmodal interactions: lessons from
synesthesia. In: Visual Perception, Part 2. Progress in Brain Research,
Volume 155. 1404 downloads from 17 countries.
http://eprints.assc.caltech.edu/224/
2. David, Elodie and Laloyaux, Cédric and Devue, Christel and Cleeremans,
Axel (2007) Change blindness to gradual changes in facial expressions.
Psychologica Belgica, in press. 1299 downloads from 12 countries.
http://eprints.assc.caltech.edu/256/
3. Koriat, A. (2006) Metacognition and Consciousness. In: Cambridge handbook
of consciousness. Cambridge University Press, New York, USA. 1088 downloads
from 21 countries. http://eprints.assc.caltech.edu/175/
4. Mashour, George A. (2007) Inverse Zombies, Anesthesia Awareness, and the
Hard Problem of Unconsciousness. In: 11th Annual Meeting of the ASSC, Las
Vegas. 976 downloads from 18 countries. http://eprints.assc.caltech.edu/294/
5. Rosenthal, David (2007) Consciousness and its function. In: 11th annual
meeting of the Association for the Scientific Study of Consciousness, 22-25
June 2007, Las Vegas, USA. 971 downloads from 19 countries.
http://eprints.assc.caltech.edu/293/

Delayed maturation of the cortex in children with ADHD

From Shaw et al., a very straightforward study showing that normal thickness of the cerebral cortex develops more slowly in children with attention deficit hyperactivity disorder. This kind of finding makes it even more disturbing that ADHD continues to be pervasively over-diagnosed in children, who are then drugged with Ritalin when they should just be left alone to let things straighten out in their own good time.

There is controversy over the nature of the disturbance in brain development that underpins attention-deficit/hyperactivity disorder (ADHD). In particular, it is unclear whether the disorder results from a delay in brain maturation or whether it represents a complete deviation from the template of typical development. Using computational neuroanatomic techniques, we estimated cortical thickness at >40,000 cerebral points from 824 magnetic resonance scans acquired prospectively on 223 children with ADHD and 223 typically developing controls. With this sample size, we could define the growth trajectory of each cortical point, delineating a phase of childhood increase followed by adolescent decrease in cortical thickness (a quadratic growth model). From these trajectories, the age of attaining peak cortical thickness was derived and used as an index of cortical maturation. We found maturation to progress in a similar manner regionally in both children with and without ADHD, with primary sensory areas attaining peak cortical thickness before polymodal, high-order association areas. However, there was a marked delay in ADHD in attaining peak thickness throughout most of the cerebrum: the median age by which 50% of the cortical points attained peak thickness for this group was 10.5 years (SE 0.01), which was significantly later than the median age of 7.5 years (SE 0.02) for typically developing controls. The delay was most prominent in prefrontal regions important for control of cognitive processes including attention and motor planning. Neuroanatomic documentation of a delay in regional cortical maturation in ADHD has not been previously reported.

Figure - The age of attaining peak cortical thickness in children with ADHD compared with typically developing children. (A) dorsal view of the cortical regions where peak thickness was attained at each age (shown, ages 7–12) in ADHD (Upper) and typically developing controls (Lower). The darker colors indicate regions where a quadratic model was not appropriate (and thus a peak age could not be calculated), or the peak age was estimated to lie outside the age range covered. Both groups showed a similar sequence of the regions that attained peak thickness, but the ADHD group showed considerable delay in reaching this developmental marker. (B) Right lateral view of the cortical regions where peak thickness was attained at each age (shown, ages 7–13) in ADHD (Upper) and typically developing controls (Lower). Again, the delay in ADHD group in attaining peak cortical thickness is apparent.

A happy ending.....

Here is a feel-good story to start the week...

Good feelings.....

A bit off the track for this blog, but it is the season for good feelings, so I pass on this alternative video for the new new Erasure single "I Could Fall In Love With You" (which I saw during happy hour yesterday at a video bar, and then found on YouTube).

Brief exposure to media violence alters cortical networks regulating reactive aggression.

This article from Kelly et al. in PLoS One biology is worth a look...here are some clips:

Media depictions of violence, although often claimed to induce viewer aggression, have not been shown to affect the cortical networks that regulate behavior...Using functional magnetic resonance imaging (fMRI), we found that repeated exposure to violent media, but not to other equally arousing media, led to both diminished response in right lateral orbitofrontal cortex (right ltOFC) and a decrease in right ltOFC-amygdala interaction. Reduced function in this network has been previously associated with decreased control over a variety of behaviors, including reactive aggression. Indeed, we found reduced right ltOFC responses to be characteristic of those subjects that reported greater tendencies toward reactive aggression. Furthermore, the violence-induced reduction in right ltOFC response coincided with increased throughput to behavior planning regions...These novel findings establish that even short-term exposure to violent media can result in diminished responsiveness of a network associated with behaviors such as reactive aggression.

The spotlight of our attention blinks ~ 7 times per second

This work argues that when we try to attend to multiple relevant targets we do so sequentially rather regarding them in parallel, at a rate of about 7 items per second. I was unable to download the supplement describing the mathematical details of the psychometric modeling they used to distinguish sequential from parallel. Here is the abstract from the article by VanRullen et al.:

Increasing evidence suggests that attention can concurrently select multiple locations; yet it is not clear whether this ability relies on continuous allocation of attention to the different targets (a "parallel" strategy) or whether attention switches rapidly between the targets (a periodic "sampling" strategy). Here, we propose a method to distinguish between these two alternatives. The human psychometric function for detection of a single target as a function of its duration can be used to predict the corresponding function for two or more attended targets. Importantly, the predicted curves differ, depending on whether a parallel or sampling strategy is assumed. For a challenging detection task, we found that human performance was best reflected by a sampling model, indicating that multiple items of interest were processed in series at a rate of approximately seven items per second. Surprisingly, the data suggested that attention operated in this periodic regime, even when it was focused on a single target. That is, attention might rely on an intrinsically periodic process.

Voluntary movements influence what we see

If our left and right eyes are shown different figures, a competition ensues during which we alternatively perceive one or the other of the figures. Maruya et al. do experiments showing that physical body movements that correlate with one of the figures can enhance the duration of the intervals during which that figure is being seen. This is a nice example of the influence of action on perception. Here is their abstract, a figure, and a clip of their discussion:

Converging lines of evidence point to a strong link between action and perception. In this study, we show that this linkage plays a role in controlling the dynamics of binocular rivalry, in which two stimuli compete for perceptual awareness. Observers dichoptically viewed two dynamic rival stimuli while moving a computer mouse with one hand. When the motion of one rival stimulus was consistent with observers' own hand movements, dominance durations of that stimulus were extended and, remarkably, suppression durations of that stimulus were abbreviated. Additional measurements revealed that this change in rivalry dynamics was not attributable to observers' knowledge about the condition under test. Thus, self-generated actions can influence the resolution of perceptual conflict, even when the object being controlled falls outside of visual awareness.

Figure - Schematic depiction of the rivalry stimuli (a) and diagrams illustrating the four kinds of trials (b). In the experiment, the reversed configuration of the stimuli, with the sphere exposed to the left eye and the grating exposed to the right eye, was also used. In (b), each diagram shows the dots' movement, the observer's hand movement, and the observer's perception of the stimuli, as a function of time. The diagrams in the upper row illustrate the sphere-dominant condition, and the diagrams in the lower row illustrate the sphere-suppressed condition; manual (MAN) trials are shown on the left, and the corresponding automatic trials are shown on the right. The dashed orange outlines indicate the period during which sphere rotation followed the rotation in the training phase, and the green arrows show the correspondence between the sphere-rotation profiles in manual and automatic trials (see the text).

It is well established that the dynamics of binocular rivalry are governed by a host of stimulus variables—including contrast, motion, and figural complexity—that, together, fall within a category defined as "stimulus strength." In our study, motor control behaved as if it, too, belonged in this category. But by what means could motor control affect the stimulus strength of a rival target? One reasonable hypothesis can be derived from the widely held view that visually guided actions are mediated by neural events in brain areas forming the so-called dorsal-stream pathway (Goodale & Milner, 1992). Among other things, this pathway is specialized for visuo-motor transformations underlying motor planning of intentional actions (Andersen & Buneo, 2002). It is also known (Fang & He, 2005) that neural activity within this pathway remains strong during both dominance and suppression phases of binocular rivalry, unlike activity in the ventral-stream pathway, where activity fluctuates during rivalry. Thus, it is conceivable that during both dominance and suppression phases, actions and their visual consequences are registered within dorsal-stream structures involved in the control of visually guided actions. Through feedback, lateral interconnections, or both, this dorsal-stream activity, in turn, could modulate neural events in brain areas where rivalry does transpire.

Scientific Imagery

During 1959-62 I did research on the blood oxygen transport protein Hemoglobin, and I remember how excited I was by the Harvard lectures at which Perutz and Kendrew presented the first three dimensional protein structures determined by X-ray diffraction. The figure at left showing the structure of the muscle oxygen storage protein myoglobin is from a 1962 Scientific American article by Kendrew.

Goodsell and Johnson, in an article in PLoS Biology, describe several of the challenges facing artists who try to represent complex biological structures, who must selectively disclose, distort, and fill in gaps. The article contains several elegant graphics.

Subliminal Smells Can Guide Social Preferences

Here is the abstract of an interesting article by Li et al. in Psychological Science, followed by a figure showing the experimental paradigm:

It is widely accepted that unconscious processes can modulate judgments and behavior, but do such influences affect one's daily interactions with other people? Given that olfactory information has relatively direct access to cortical and subcortical emotional circuits, we tested whether the affective content of subliminal odors alters social preferences. Participants rated the likeability of neutral faces after smelling pleasant, neutral, or unpleasant odors delivered below detection thresholds. Odor affect significantly shifted likeability ratings only for those participants lacking conscious awareness of the smells, as verified by chance-level trial-by-trial performance on an odor-detection task. Across participants, the magnitude of this priming effect decreased as sensitivity for odor detection increased. In contrast, heart rate responses tracked odor valence independently of odor awareness. These results indicate that social preferences are subject to influences from odors that escape awareness, whereas the availability of conscious odor information may disrupt such effects.

Figure - The experimental paradigm. First, participant specific odor detection thresholds were determined using an ascending-staircase procedure. Then, participants completed an odor-detection and likeability judgment task. In this example, the detection threshold was at dilution 20, so dilution 22 was used in the main task. In that task, participants sniffed a bottle, indicated whether or not it contained an odor, viewed a face stimulus, and finally rated the likeability of the face. For a subset of the participants, heart rate was recorded.

Using Neuroimaging to Resolve the Psi Debate

Moulton and Kosslyn offer a study in J. Cog. Neurosci attempting to find evidence for the psi effect in brain imaging experiments. Here is their abstract, followed by some edited clips and a figure from the paper:

Parapsychology is the scientific investigation of apparently paranormal mental phenomena (such as telepathy, i.e., "mind reading"), also known as psi. Despite widespread public belief in such phenomena and over 75 years of experimentation, there is no compelling evidence that psi exists. In the present study, functional magnetic resonance imaging (fMRI) was used in an effort to document the existence of psi. If psi exists, it occurs in the brain, and hence, assessing the brain directly should be more sensitive than using indirect behavioral methods (as have been used previously). To increase sensitivity, this experiment was designed to produce positive results if telepathy, clairvoyance (i.e., direct sensing of remote events), or precognition (i.e., knowing future events) exist. Moreover, the study included biologically or emotionally related participants (e.g., twins) and emotional stimuli in an effort to maximize experimental conditions that are purportedly conducive to psi. In spite of these characteristics of the study, psi stimuli and non-psi stimuli evoked indistinguishable neuronal responses—although differences in stimulus arousal values of the same stimuli had the expected effects on patterns of brain activation. These findings are the strongest evidence yet obtained against the existence of paranormal mental phenomena.

In our experiment, participants played one of two roles: "sender" and "receiver." On each trial, sender participants viewed a randomly selected target stimulus from outside the scanner (see Figure), and tried to send this information to the receiver participant by mental means alone. While the senders were doing this, receiver participants completed a simple binary guessing task, and functional magnetic resonance imaging (fMRI) was used to monitor their brain activity. On each trial of the guessing task, the receivers sequentially viewed two stimuli, guessed which one was the stimulus being "sent" (i.e., the psi stimulus), and then saw the psi stimulus a second time. This paradigm allowed us simultaneously to test all three hypothesized mechanisms of psi: telepathy (i.e., "mind reading"), clairvoyance (i.e., direct sensing of remote events), and precognition (i.e., knowing future events). The sender served as the potential telepathic source, the sender's computer monitor served as the potential clairvoyance source, and the second presentation of the psi stimulus served as the potential precognition source.

Figure 1 A schematic of one trial. In this trial for the receiver, the non-psi stimulus appears first and the psi stimulus second. The third stimulus presentation (feedback) in each trial is always the same as the psi stimulus. The sender sees only the psi stimulus for each trial.

The results support the null hypothesis that psi does not exist. The brains of our participants—as a group and individually—reacted to psi and non-psi stimuli in a statistically indistinguishable manner. Given the relatively large number of participants, the use of fixed-effects statistics, the extensive activation elicited separately by both types of stimuli, the subtle psychological effects revealed in the much smaller data set from a single participant, and the non-psi effects we documented on a group level using identical statistical criteria, a lack of statistical power does not reasonably explain our results. Even if the psi effect were very transient, as are many mental events, it should have left a footprint that could be detected by fMRI—as did the other subtle effects we detected. In particular, the large and massively significant activation revealed by our arousal contrast shows that that the psi effect, if it exists, must be substantially smaller than the effect of arousal on brain activity.

But what of the truism that one cannot affirm the null hypothesis? We note that some null results should be taken more seriously than others. ....Consider the possibility of water on Mars. If a set of close-up images of its surface failed to capture frozen lakes, few would accept the nonexistence of Martian water. Yet if a planetwide analysis of its subsurface soil content failed to show telltale signs of water, most would accept the null hypothesis of a Martian desert. Past null results from parapsychology are comparable to scattered snapshots of the surface in that they measure a small sample of outwardly observable variables. The current neuroimaging approach, however, seeks anomalous knowledge at its source, inside the brain, using methods validated by cognitive neuroscience. It is also exhaustive...the study incorporated methodological variables (e.g., biological and emotional relatedness of participants, evocative stimuli) widely considered to facilitate psi by parapsychologists. As such, the current null results do not simply fail to support the psi hypothesis: They offer strong evidence against it. If these results are replicated over a range of participants and situational contexts, the case will become increasingly strong, with as much certainty as is allowed in science, that psi does not exist.