Remembering small pattern differences.

Bannerman and Sprengel discuss (PDF here) and offer perspective on work of McHugh et al. from Tonegawa's laboratory showing synaptic details of how the mouse hippocampus carries out pattern separation. The findings explain how we detect small changes in our environment, perhaps allowing us to update and guide our choices. They offer a nice graphic of the hippocampus, which is central in this processes.

Knowing what, when, and where. In the mouse brain, the dentate gyrus region of the hippocampus can detect small changes in the animal's spatial environment and differentiate between recent experiences that occur in the same place. The white arrows trace a path of signaling between different regions of the hippocampus. Sensory information can enter the hippocampus from the entorhinal cortex and is sent back to the entorhinal cortex after processing.

Can Systems Biology integrate Chinese and Western Meidicine?

Here is the PDF of an interesting article by Jane Qui that I pass on in part because I have been struck by the number of emails I have received from readers of this blog asking questions about alternative medicine and cures (a subject on which I an NOT an expert). The article addresses the question of whether a formidable gap can be addressed:

Modern Western medicine generally prescribes treatments for specific diseases, often on the basis of their physiological cause. Traditional Chinese medicine, however, focuses on symptoms, and uses plant and animal products, minerals, acupuncture and moxibustion — the burning of the mugwort herb (Artemisia vulgaris) on or near the skin. But whether these methods are effective and, if they are, how they work remain a source of some derision. The greatest divide is in the testing. In the West, researchers test a drug's safety and efficacy in randomized, controlled trials. Traditional Chinese treatments are mixtures of ingredients, concocted on the spot on the basis of a patient's symptoms and characteristics and using theories passed down through generations.

The article discusses how researchers in China and elsewhere, meanwhile, are advocating systems biology — the study of the interactions between proteins, genes, metabolites and components of cells or organisms — as a way to assess the usefulness of traditional medicines.

Attentional expertise in long-term meditators: neural correlates

More from Richie Davidson's laboratory here at Wisconsin. The article is open-access, you can go there for the graphics:

Meditation refers to a family of mental training practices that are designed to familiarize the practitioner with specific types of mental processes. One of the most basic forms of meditation is concentration meditation, in which sustained attention is focused on an object such as a small visual stimulus or the breath. In age-matched participants, using functional MRI, we found that activation in a network of brain regions typically involved in sustained attention showed an inverted u-shaped curve in which expert meditators (EMs) with an average of 19,000 h of practice had more activation than novices, but EMs with an average of 44,000 h had less activation. In response to distracter sounds used to probe the meditation, EMs vs. novices had less brain activation in regions related to discursive thoughts and emotions and more activation in regions related to response inhibition and attention. Correlation with hours of practice suggests possible plasticity in these mechanisms.

Internet connectivity model

Don't ask me what k-shell decomposition is, but Carmi et al. (PDF here) perform an analysis of the internet using it to yield an interesting model of internet connectivity and a summary graphic. Analysis of this sort is also applied to brain networks. Their abstract, followed by the graphic:

We study a map of the Internet (at the autonomous systems level), by introducing and using the method of k-shell decomposition and the methods of percolation theory and fractal geometry, to find a model for the structure of the Internet. In particular, our analysis uses information on the connectivity of the network shells to separate, in a unique (no parameters) way, the Internet into three subcomponents: (i) a nucleus that is a small ({approx}100 nodes), very well connected globally distributed subgraph; (ii) a fractal subcomponent that is able to connect the bulk of the Internet without congesting the nucleus, with self-similar properties and critical exponents predicted from percolation theory; and (iii) dendrite-like structures, usually isolated nodes that are connected to the rest of the network through the nucleus only. We show that our method of decomposition is robust and provides insight into the underlying structure of the Internet and its functional consequences. Our approach of decomposing the network is general and also useful when studying other complex networks.

Visualization of our data of the Internet at the AS level. (Upper) A plot of all nodes, ordered by their k-shell indices, using the program of ref. 13. The legend to the left denotes degree, and the legend to the right denotes k-shell index. (Lower) A schematic plot of the suggested Medusa model decomposition of the AS level Internet into three components.

Thoughts on, reservations about, science blogging...

I've just had a brief exchange with David Dobbs, who wrote the piece on Williams Syndrome mentioned a few posts back. He has decided to cut back on blogging, and I found his comments on this, and a reaction to comments by Andrew Sullivan, worth passing on. The mindsets of blogging and book writing are very different. (And...the reason I haven't gone beyond very preliminary efforts to do a second version of my "Biology of Mind" book.)

Whole brain structural networks - some neat movies

Hagmann et al propose that diffusion MRI provides an efficient methodology to generate large, comprehensive and individual white matter connectional datasets of the living or dead, human or animal brain. This non-invasive tool enables study of the basic and potentially complex network properties of the entire brain. For two human subjects they find that their individual brain networks have an exponential node degree distribution and that their global organization is in the form of a small world. The link to their article takes you to three fascinating movies: one showing whole brain tractography, a second showing partition of the white-gray matter interface into approximately 1000 regions of interest, and the third, included here via YouTube so you don't have to download the quicktime movie, showing connections between different visual areas.

A musical interlude...

I put my playing of a Debussy Reverie on YouTube about 10 months ago, and am completely amazed that it has by now had ~18,000 viewings, and over 50 largely constructive comments, many of which suggested to "slow down." So, I did a second version and posted it two months ago, which I pass on here. Response has been more favorable.

Genetics and tonal languages

It is likely that there are heritable differences of brain structure and function that affect language acquisition and usage...cognitive biases in a population of acquirers could influence the direction of language change across generations. These biasing effects could result in linguistic differences between populations, producing nonspurious (causal) correlations between genetic and linguistic diversities. Dediu and Ladd:

... propose that the linguistic typology of tone is affected by such a bias. Human languages differ typologically in the way they use voice fundamental frequency (pitch). All languages use consonants and vowels to distinguish one word or grammatical category from another, but, in addition, so-called "tone languages" (e.g., Chinese) use pitch for this purpose as well, whereas "non-tone languages" (e.g., English) use pitch only at sentence level (to convey emphasis, emotion, etc.). In tone languages, that is, pitch is organized into tone phonemes that are functionally comparable with consonant and vowel phonemes. Tone languages are the norm in sub-Saharan Africa and are very common in continental and insular southeast Asia. They are rare in the rest of Eurasia, North Africa, and Australia. They are relatively common in Central America, the Caribbean, and the Amazon basin, and occur sporadically elsewhere among the aboriginal languages of the Americas..

Here is their Abstract:

The correlations between interpopulation genetic and linguistic diversities are mostly noncausal (spurious), being due to historical processes and geographical factors that shape them in similar ways. Studies of such correlations usually consider allele frequencies and linguistic groupings (dialects, languages, linguistic families or phyla), sometimes controlling for geographic, topographic, or ecological factors. Here, we consider the relation between allele frequencies and linguistic typological features. Specifically, we focus on the derived haplogroups (note: these are sets of nucleotide polymorphisms) of the brain growth and development-related genes ASPM and Microcephalin, which show signs of natural selection and a marked geographic structure, and on linguistic tone, the use of voice pitch to convey lexical or grammatical distinctions. We hypothesize that there is a relationship between the population frequency of these two alleles and the presence of linguistic tone and test this hypothesis relative to a large database (983 alleles and 26 linguistic features in 49 populations), showing that it is not due to the usual explanatory factors represented by geography and history. The relationship between genetic and linguistic diversity in this case may be causal: certain alleles can bias language acquisition or processing and thereby influence the trajectory of language change through iterated cultural transmission.

Most popular consciousness papers for June 2007

That is, the five most downloaded from the eprint archive maintained by the Association for the Scientific Study of Consciousness.

1. Rosen, Alan and Rosen, David B. (2006) The Design of a
Sensation-generating Mechanism in the Brain: A first step towards a
quantitative definition of consciousness. In: Consciousness and
Cognition (1223 downloads from 9 countries).
http://eprints.assc.caltech.edu/195/

2. Sagiv, Noam and Ward, Jamie (2006) Crossmodal interactions: lessons
from synesthesia. In: Visual Perception, Part 2 (1171 downloads from
20 countries). http://eprints.assc.caltech.edu/224/

3. Ruby, Perrine and Legrand, Dorothée (2007) Neuroimaging the self?
In: Sensorimotor foundations of higher cognition. OUP (882 downloads
from 14 countries). http://eprints.assc.caltech.edu/275/

4. Koriat, A. (2006) Metacognition and Consciousness. In: Cambridge
handbook of consciousness. CUP (804 downloads from 15 countries).
http://eprints.assc.caltech.edu/175/

5. Windt, Jennifer Michelle and Metzinger, Thomas (2006) The
philosophy of dreaming and self-consciousness: What happens to the
experiential subject during the dream state? In: The new science of
dreaming (780 downloads from 22 countries).
http://eprints.assc.caltech.edu/200/

Modulating emotional appraisal by false physiological feedback.

Grey et al. examine how emotional appraisal is influenced by physiological feedback. Their observations make me wonder whether trying the opposite trick, giving false feedback that suggests less autonomic arousal, could chill out reactions to an emotional stimulus... Their main points:

James and Lange proposed that emotions are the perception of physiological reactions. Two-level theories of emotion extend this model to suggest that cognitive interpretations of physiological changes shape self-reported emotions. Correspondingly false physiological feedback of evoked or tonic bodily responses can alter emotional attributions. Moreover, anxiety states are proposed to arise from detection of mismatch between actual and anticipated states of physiological arousal. However, the neural underpinnings of these phenomena previously have not been examined.

We undertook a functional brain imaging (fMRI) experiment to investigate how both primary and second-order levels of physiological (viscerosensory) representation impact on the processing of external emotional cues. Twelve participants were scanned while judging face stimuli during both exercise and non-exercise conditions in the context of true and false auditory feedback of tonic heart rate. We observed that the perceived emotional intensity/salience of neutral faces was enhanced by false feedback of increased heart rate. Regional changes in neural activity corresponding to this behavioural interaction were observed within included right anterior insula, bilateral mid insula, and amygdala. In addition, right anterior insula activity was enhanced during by asynchronous relative to synchronous cardiac feedback even with no change in perceived or actual heart rate suggesting this region serves as a comparator to detect physiological mismatches. Finally, BOLD activity within right anterior insula and amygdala predicted the corresponding changes in perceived intensity ratings at both a group and an individual level.

Our findings identify the neural substrates supporting behavioural effects of false physiological feedback, and highlight mechanisms that underlie subjective anxiety states, including the importance of the right anterior insula in guiding second-order “cognitive” representations of bodily arousal state.

Williams Syndrome - evidence for a discrete social brain

David Dobbs offers a very well written essay (PDF here) on Williams Syndrome in the Sunday New York Times Magazine (7/8/07). The syndrome is caused by a well-defined deletion in chromosome 7 that occasionally occurs during the synthesis of egg or sperm cells. Patients have a low IQ (~60) and compromised spatial skill and analytical thought, but are hyper-sociable and friendly, very talkative. An pathway from the orbitofrontal (OFC) cortex to the amygdala that usually signals dangerous or angry faces is inactive; but curiously the OFC-amygdala connection still works normally for nonsocial threats such as pictures of snakes, sharks or car crashes. The existence of this syndrome provides perhaps the strongest evidence for genetically and developmentally distinct class of 'social brain' mechanisms distinct from other higher sensory, motor, and analytical skills.

A Sunday Walk....

Around my house on Twin Valley Road in Town of Middleton, Wisconsin. (It is a stone schoolhouse built in 1860, converted to a residence).

How pain preempts cognition - and about itching

I found these two articles on pain and itching interesting, particularly since I've been going through an orgy of both after exposing myself to poison oak or ivy while working in the yard. Bingel et al. show some brain correlates of why I found it difficult to focus on normal cognitive activities during this period:

It is well known that pain attracts attention and interferes with cognition. Given that the mechanisms behind this phenomenon are largely unknown, we used functional magnetic resonance imaging and presented visual objects with or without concomitant pain stimuli. To test for the specificity of pain, we compared this modulatory effect with a previously established modulatory effect of working memory on visual object processing. Our data showed a comparable behavioral effect of both types of modulation and identified the lateral occipital complex (LOC) as the site of modulation in the ventral visual stream, for both pain and working memory. However, the sources of these modulatory effects differed for the two processes. Whereas the source of modulation for working memory could be attributed to the parietal cortex, the modulatory effect of pain was observed in the rostral anterior cingulate cortex (rACC), an area ideally suited to link pain perception and attentional control.
A) fMRI effects of the interaction of background visibility with working memory load were observed in bilateral LOC, reflecting a phasic modulation of LOC activity.
(B) Corresponding activation and parameter estimates related to the interaction of Pain × Visibility.

Now, on to itching (also central to my poison oak story, still going on....). Johanek et al. note a curious distinction between histamine induced itching and itching caused by cutaneous application of spicules from the cowhage plant. They show a different class of afferent C-fiber afferents signaling non-histamine induced itching:

The neuronal pathways for itch have been characterized mainly based on responses to histamine. Intracutaneous application of histamine produces intense itch and a large area of axon-reflexive vasodilation ("flare") around the application site. Both phenomena are thought to be mediated through neuronal activity in itch-specific, mechanoinsensitive C-fiber afferents (CMi). However, mechanical and electrical stimuli that do not activate CMi fibers can cause the sensation of itch, and itch may occur without flare, suggesting that other neuronal itch pathways exist. Because cutaneous application of spicules from the plant Mucuna pruriens (cowhage) has been anecdotally reported to produce itch without flare, we performed psychophysical experiments to investigate whether the mechanisms underlying cowhage- and histamine-induced itch differ. Although histamine and cowhage produced itch of similar magnitude, the itch to cowhage was not correlated with the itch to histamine; some subjects had intense itch to cowhage and little itch to histamine and visa versa. Laser Doppler measurements of blood flow revealed that histamine led to a large area of vasodilation, whereas cowhage produced vasodilation restricted to the application site. Pretreatment of the skin with an antihistamine blocked the itch produced by histamine but did not prevent cowhage-induced itch. Desensitization of the skin with topical capsaicin abolished cowhage-induced itch but did not significantly alter histamine-induced itch. These findings indicate that cowhage itch is signaled through a population of capsaicin-sensitive afferent nerve fibers that is distinct from CMi fibers mediating histamine-induced itch. Cowhage may be useful to investigate the neural pathway mediating nonhistaminergic itch.

Negative suggestions enhancing pain -an antidote?

Benedetti et al. provide an interesting review of the nocebo effect (the anticipation of pain enhancing its magnitude). This is the opposite of the placebo effect, where a more positive expectation can lower perceived pain. Their article (PDF here) provides some interesting graphics of brain imagining showing this effect, and discusses relevant brain receptors.
Recent experimental evidence indicates that negative verbal suggestions induce anticipatory anxiety about the impending pain increase, and this verbally-induced anxiety triggers the activation of cholecystokinin (CCK) which, in turn, facilitates pain transmission. CCK-antagonists have been found to block this anxiety-induced hyperalgesia, thus opening up the possibility of new therapeutic strategies whenever pain has an important anxiety component.

Rodent Altruism - Lending an Anonymous Paw

Krista Zala writes a nice summary of work by Rutte and Taborsky. Some clips:

Rats given a helping paw are more prone to helping others--even complete strangers. This suggests that the animals' social life may be richer than we thought...Many animals, including rats, demonstrate direct reciprocity--described as "I'll help you if you help me." But generalized reciprocity, in which individuals remember how they were treated in the recent past and apply it to others, including strangers, has been thought to be a uniquely human trait...However, previous studies haven't specifically looked for generalized reciprocity in other animals.



To find out if rats have this capacity, Rutte and Michael Taborsky of the University of Bern in Switzerland trained rats to pull a lever that would deliver an oat flake reward to another rat on the other side of a wire mesh wall in a shared cage. Some of these rats were then put on the receiving side, paired for several days with either other rats trained to be helpful—-three different ones over the span--or with untrained rats that didn't pull the lever and provide food. After several days of living with such generous or not-so-generous neighbors, these test rats were then switched back to the lever side of the cage, paired with a new neighbor rat, and watched to see if they would provide food for it. Rats who had been paired with food-providing neighbors helped their new partner more often than those who had had unhelpful neighbors. Rutte's team also found that when a test rat was paired with one of the rats that had earlier provided it with oak flakes, it pulled the food lever even more--showing direct reciprocity. When the cage was empty of any neighbor rat, it barely pulled the food lever at all.

In a pack of 200 rats, where it's hard to remember who's been helpful and who hasn't, a general willingness to help others makes sense as a strategy...It may be a mechanism for how cooperation can evolve when you cannot recognize your partner...rats are notoriously bad at remembering other individuals.

Looking into the prevalence of generalized reciprocity among social and nonsocial animals may help our understanding of the evolution of cooperation.

The New York Times Science section has now also done a popular summary of this work (PDF here), and the graphic above is from that review.

Altruistic Chimps and Children

As a companion to the blog posting on helping rodents, this work from Tomasello's laboratory. The article has some nice videos. Here is the author's summary:

Debates about altruism are often based on the assumption that it is either unique to humans or else the human version differs from that of other animals in important ways. Thus, only humans are supposed to act on behalf of others, even toward genetically unrelated individuals, without personal gain, at a cost to themselves. Studies investigating such behaviors in nonhuman primates, especially our close relative the chimpanzee, form an important contribution to this debate. Here we present experimental evidence that chimpanzees act altruistically toward genetically unrelated conspecifics. In addition, in two comparative experiments, we found that both chimpanzees and human infants helped altruistically, regardless of any expectation of reward, even when some effort was required, and even when the recipient was an unfamiliar individual—all features previously thought to be unique to humans. The evolutionary roots of human altruism may thus go deeper than previously thought, reaching as far back as the last common ancestor of humans and chimpanzees.

Neuroimaging of emotions driving political strategy...

My October 23 post mentioned the work of Westen, who has used functional neuroimaging to show how emotions prevail over reason when people rationalize their political choices. This material - up to date neuroscience of decision making - has been taken up and absorbed as a guide to campaign strategy in an amazingly short time, with democratic party strategists particularly engaged by Westen's recent book, “The Political Brain: The Role of Emotion in Deciding the Fate of the Nation” (Public Affairs).

Westen takes the unlikely position that the Democratic Party should, for the most part, forget about issues, policies, even facts, and instead focus on feelings. His book takes a very different tack than, say, “What’s the Matter With Kansas?” by Thomas Frank or Al Gore’s “Assault on Reason,” which try to explain voter behavior in terms of self-interest and factual analysis.

The recent review of Westen's book by Patricia Cohen in the New York Times, notes that Westen has by now given numerous talks to political groups and set up a political consulting company. She notes Bill Clinton's positive reaction to the book, as he "particularly liked the discussion of how one could evoke emotion without being intellectually dishonest.” Cohen's review is worth reading (PDF here).

In this vein, it is interesting that Louis Menand in a recent New Yorker review titled "The Fractured Franchise" has an elegant discussion of evidence that most voters are massively ignorant and misinformed about political reality (PDF here). Thus, even when 'democracy works' the results can be a disaster. (So we should prefer rule by economists?) He reviews the recent book by Bryan Caplan, “The Myth of the Rational Voter: Why Democracies Choose Bad Politics” (Princeton; $29.95). (By the way, see also Menand's earlier article "The Unpolitical Animal." He is a brilliant guy. )

Hi-Tech fMRI lie detection - another scam?

Margaret Talbot writes an interesting article in The New Yorker (PDF here) about the current hype over lie detection using brain scanning techniques, and the sprouting of numerous companies wanting to sell their services to private investigators, police departments, U.S. and foreign government agencies, etc. The article is a broad discussion of lie detection also by other physiological indicators such as skin conductance and blood pressure. Most interesting to me were the critical points raised. Here are a few clips from the article:

Paul Bloom, a cognitive psychologist at Yale, believes that brain imaging has a beguiling appeal beyond its actual power to explain mental and emotional states. "Psychologists can be heard grousing that the only way to publish in Science or Nature is with pretty color pictures of the brain," he wrote in an essay for the magazine Seed. "Critical funding decisions, precious column inches, tenure posts, science credibility, and the popular imagination have all been influenced by fMRI's seductive but deceptive grasp on our attentions." Indeed, in the past decade, Nature alone has published nearly a hundred articles involving fMRI scans. The technology is a remarkable tool for exploring the brain, and may one day help scientists understand much more about cognition and emotion. But enthusiasm for brain scans leads people to overestimate the accuracy with which they can pinpoint the sources of complex things like love or altruism, let alone explain them.

Brain scans enthrall us, in part, because they seem more like "real" science than those elaborate deductive experiments that so many psychologists perform. In the same way that an X-ray confirms a bone fissure, a brain scan seems to offer an objective measure of mental activity. And, as Bloom writes, fMRI research "has all the trappings of work with great lab-cred: big, expensive, and potentially dangerous machines, hospitals and medical centers, and a lot of people in white coats."

Deena Skolnick Weisberg, a graduate student at Yale, has conducted a clever study, to be published in the Journal of Cognitive Neuroscience, which points to the outsized glamour of brain-scan research. She and her colleagues provided three groups--neuroscientists, neuroscience students, and ordinary adults--with explanations for common psychological phenomena (such as the tendency to assume that other people know the same things we do). Some of these explanations were crafted to be bad. Weisberg found that all three groups were adept at identifying the bad explanations, except when she inserted the words "Brain scans indicate." Then the students and the regular adults became notably less discerning. Weisberg and her colleagues conclude, "People seem all too ready to accept explanations that allude to neuroscience."

Nancy Kanwisher, a cognitive scientist at M.I.T., relies a great deal on MRI technology. In 1997, she identified an area near the bottom of the brain that is specifically involved in perceiving faces. She has become a pointed critic of the rush to commercialize brain imaging for lie detection, and believes that it's an exaggeration even to say that research into the subject is "preliminary." The tests that have been done, she argues, don't really look at lying. "Making a false response when instructed to do so is not a lie," she says. The ninety-per-cent "accuracy" ascribed to fMRI lie detection refers to a scenario so artificial that it is nearly meaningless. To know whether the technology works, she believes, "you'd have to test it on people whose guilt or innocence hasn't yet been determined, who believe the scan will reveal their guilt or innocence, and whose guilt or innocence can be established by other means afterward." In other words, you'd have to run a legal version of a clinical trial, using real suspects instead of volunteers.

She points out that the various brain regions that appear to be significantly active during lying are "famous for being activated in a wide range of different conditions--for almost any cognitive task that is more difficult than an easier task." She therefore believes that fMRI lie detection would be vulnerable to countermeasures--performing arithmetic in your head, reciting poetry--that involve concerted cognitive effort. Moreover, the regions that allegedly make up the brain's "lying module" aren't that small...Saying 'You have activation in the anterior cingulate' is like saying 'You have activation in Massachusetts.' "

Kanwisher's complaint suggests that fMRI technology, when used cavalierly, harks back to two pseudosciences of the eighteenth and nineteenth centuries: physiognomy and phrenology. Physiognomy held that a person's character was manifest in his facial features; phrenology held that truth lay in the bumps on one's skull. In 1807, Hegel published a critique of physiognomy and phrenology in "The Phenomenology of Spirit." In that work, as the philosopher Alasdair MacIntyre writes, Hegel observes that "the rules that we use in everyday life in interpreting facial expression are highly fallible." (A friend who frowns throughout your piano recital might explain that he was actually fuming over an argument with his wife.) Much of what Hegel had to say about physiognomy applies to modern attempts at mind reading.

Elizabeth Phelps, a prominent cognitive neuroscientist at N.Y.U., who studies emotion and the brain, questions another basic assumption behind all lie-detection schemes--that telling a falsehood creates conflict within the liar. With the polygraph, the assumption is that the conflict is emotional: the liar feels guilty or anxious, and these feelings produce a measurable physiological response. With brain imaging, the assumption is that the conflict is cognitive:the liar has to work a little harder to make up a story, or even to stop himself from telling the truth. Neither is necessarily right. "Sociopaths don't feel the same conflict when they lie," Phelps says. "The regions of the brain that might be involved if you have to inhibit a response may not be the same when you're a sociopath, or autistic, or maybe just strange. Whether it's an emotional or a cognitive conflict you're supposed to be exhibiting, there's no reason to assume that your response wouldn't vary depending on what your personal tendencies are--on who you are."

When watching a tactile stroke is the same as receiving one.

An interesting report from Banissy and Ward (PDF here)... People who have 'mirror-touch' synesthesia, when watching another person being touched, have the same experience as being touched themselves...an extreme form of empathy! They developed a protocol to provide evidence for the authenticity of this form of synesthesia, in which participants have difficulty in discriminating between actual and synesthetic touch. Their abstract:

Watching another person being touched activates a similar neural circuit to actual touch and, for some people with 'mirror-touch' synesthesia, can produce a felt tactile sensation on their own body. In this study, we provide evidence for the existence of this type of synesthesia and show that it correlates with heightened empathic ability. This is consistent with the notion that we empathize with others through a process of simulation.

Making up our Minds...

Rebecca Saxe's review of "Making Up the Mind" by Chris Frith (Blackwell, 2007, 232 pp, paperback, $24.99) is a very nice summary of why we need an empirical science of the mind that does not rely on introspection, noting that experiences of how minds work, both our own and other people's, are just fantasies whose predictions often coincide with reality. Frith's book argues that there is no qualitative difference between perceiving the outside world and our own actions in it, compared with trying to infer the thoughts, feelings and goals inside other people's heads. Here is Saxe's review:

Perceiving the outside world and one's own actions in it might seem easy, at least when compared with trying to infer the thoughts, feelings and goals inside other people's heads. These intuitions are wrong, however, and debunking them is the main task of Chris Frith's new book, Making Up the Mind. The apparently effortless perceptions of the world and the self mask sophisticated computation and 'unconscious inferences'. On the other hand, he claims, these same kinds of inferences support access to other people's feelings and intentions. There is no qualitative difference between perceiving minds and perceiving anything else.

If perceiving the world is a hard problem, studying these perceptions is possibly a harder one. By their nature, 'unconscious inferences' are not accessible to introspection. Indeed, the major trick of the scientific psychologist's trade is to devise alternative nonintrospective methods for studying the mind. The need for such methods arises not just because conscious experiences are 'soft', imprecise or hard to verify, the reasons that Frith entertains in his prologue. More importantly, as he shows in the rest of the book, the contents of introspection are simply unreliable as guides to the real structure of the mind.

Frith is especially enthusiastic about one such method: studying the brain. Brain function provides a window onto the intermediate stages of mental computations, between the inputs at the senses and the outputs in behavior and conscious experience. These days, this approach is called 'cognitive neuroscience' and its popularity is booming with the increasing availability of noninvasive brain scanners.

Making Up the Mind is an accessible and enthusiastic introduction to the field, and a great way to whet the appetites of smart beginners. Particularly nice is Frith's clear affection for doing science. During one experiment, he remembers, "we all had a very exciting Saturday in the imaging laboratory, which is not reflected at all in the paper we wrote about it afterwards." At another point, he expands on a reference to "my lab" with this footnote, "In the 1960s, this was a small bathroom that had been converted into a 'laboratory' by putting a sheet of hardboard over the bathtub."

Part 1 of the book covers the most charismatic discoveries of cognitive and neuropsychology, the gaps between the real world and the world constructed by the mind: phantom limbs, blindsight, anosognosia, change blindness, color constancy (including a fantastic demo in the color plates), priming, motor adaptation, illusions of causal control, synesthesia, implicit memory, dreams and hallucinations. (Surprisingly, he doesn't mention confabulation or false memories, two other famous illustrations of his thesis that our brains 'make up' our world.) The message is that nothing that appears simple or direct in our perceptions of the world, and of ourselves, can be taken for granted.

So how does the brain construct the consciously experienced world? No one knows. Instead of giving an answer, Part 2 introduces some basic concepts: neurons and synapses, associative and operant conditioning, Bayesian inference, and forward and inverse models. The result is a useful informal survey of the foundations of current research.

Finally, in Part 3, Frith turns back to problems of perception, now focusing on the question of social perception: how we can ever 'know' about someone else's thoughts, feelings or goals? The situation, Frith claims, is not as bad as it looks. Other people's actions are represented in the same way we represent our own actions, using a forward model to predict their causal effects. Frith illustrates this idea with an illusion. When a sound acts as a signal to start an action, the cause (the sound) and the effect (the hand motion) are perceived to be closer together in time than they really are, both for one's own and other people's actions, but not for an externally caused event. Another great example that Frith does not mention, which was reported by Sebanz and colleagues, is that the (task-irrelevant) direction that an arrow is pointing interferes with participants' ability to respond on the basis of color, if and only if the arrow points to another possible action, either for the participant or for another person. That is, a representation of another person's possible (but unseen) actions can compete with the participant's own action plans.

In all, Making Up the Mind is an accessible, fun and up-to-date introduction to the hot ideas and phenomena in and around cognitive neuroscience. Only the conclusion feels out of place. In it, Frith writes that we all do successfully 'read minds', achieving direct access to other people's thoughts and goals. How we take this conclusion depends on what Frith means by success. It is true that inferences about other minds are not qualitatively harder than other inferences, but neither are they (as Frith sometimes implies) any easier or more accurate. Inferences about other minds have the same structure as self-perception, going beyond the data given using a sophisticated combination of prior knowledge and current data, and then masked by an illusion of effortlessness. As a result, inferences about others are just as prone to leaps, gaps and confabulations. The conclusion ought to leave us where the book began in the prologue. Psychologists who want to study the mind scientifically do not rely on social perceptions of the participants any more than they rely on introspection, precisely because social mind-reading fails. Our experiences of how minds work, both our own and other people's, are just fantasies whose predictions often coincide with reality. That is why we still do need an empirical science of the mind.