Neural correlates of aesthetic preference - differences between men and women

The abstract from Cela-Condea et al.:

The capacity to appreciate beauty is one of our species' most remarkable traits. Although knowledge about its neural correlates is growing, little is known about any gender-related differences. We have explored possible differences between men and women's neural correlates of aesthetic preference. We have used magnetoencephalography to record the brain activity of 10 male and 10 female participants while they decided whether or not they considered examples of artistic and natural visual stimuli to be beautiful. Our results reveal significantly different activity between the sexes in parietal regions when participants judged the stimuli as beautiful. Activity in this region was bilateral in women, whereas it was lateralized to the right hemisphere in men. It is known that the dorsal visual processing stream, which encompasses the superior parietal areas, has been significantly modified throughout human evolution. We posit that the observed gender-related differences are the result of evolutionary processes that occurred after the splitting of the human and chimpanzee lineages. In view of previous results on gender differences with respect to the neural correlates of coordinate and categorical spatial strategies, we infer that the different strategies used by men and women in assessing aesthetic preference may reflect differences in the strategies associated with the division of labor between our male and female hunter-gatherer hominin ancestors.

They suggest:

...One possible explanation for the greater lateralization in men than in women could be grounded on differences between exploration strategies. Women would carry out an exploration of categorical spatial relations. The processes occurring in the right hemisphere of male participants suggest an exploration strategy based on coordinate spatial relations.
...there are other alternatives to the interpretation based on spatial exploration strategies. It is generally accepted that the right parietal cortex is associated with global visual attention and the left with local attention. Perhaps women make use of both global and local features in making their judgments, whereas men only rely on global features.
...Another hypothesis could link the observations to language. Women obtain higher scores on a diversity of verbal and language tasks. Perhaps women are more likely to associate the images with verbal labels than men, producing the lateralizing differences in neural activity.

They feel that:

...hunter-gatherer hypothesis of gender differences in spatial abilities provides the most convincing scenario. Differences in spatial ability between men and women would be associated with the division of labor between the sexes in hunting and gathering.

A map of knowledge

When we click from one page to another while looking through online scientific journals, we generate a chain of connections between things we think belong together. Now a billion such 'clickstream events' have been analyzed to map these connections on a grand scale. What emerges is a fascinating snapshot of the web of interconnections between disciplines, which some data-mining experts believe reveals the degree to which work that is not often cited — including work in the social sciences and humanities — is widely consulted and can form bridges between scientific disciplines. The authors of the maps argue that web-usage metrics give an alternative and more up-to-date view of science than existing maps and indicators, which are largely based on out-of-date citation data. (Try clicking on the map to enlarge it.)

How to lower your self control.

An interesting piece of work from Ackerman et al. We know that imagining or actively perceiving other people's actions can elicit many of the same neural and embodied responses that would occur if we performed those actions ourselves. This work shows that observing someone exerting self control sufficiently engages our empathetic mirroring of that process that it fatigues our own self control!

Acts of self-control may deplete an individual's self-regulatory resources. But what are the consequences of perceiving other people's use of self-control? Mentally simulating the actions of others has been found to elicit psychological effects consistent with the actual performance of those actions. Here, we consider how simulating versus merely perceiving the use of willpower can affect self-control abilities. In a first study, participants who simulated the perspective of a person exercising self-control exhibited less restraint over spending on consumer products than did other participants. In a second study, participants who took the perspective of a person using self-control exerted less willpower on an unrelated lexical generation task than did participants who took the perspective of a person who did not use self-control. Conversely, participants who merely read about another person's self-control exerted more willpower than did those who read about actions not requiring self-control. These findings suggest that the actions of other people may either deplete or boost one's own self-control, depending on whether one mentally simulates those actions or merely perceives them.

Gay scientists isolate christian gene.

My thanks to Mark Weber for bringing this satire to my attention.

Gesturing enhances learning in children

Goldin-Meadow and collaborators, whose work on the role of gesture in language development I have mentioned previously in two posts, now demonstrate that gesturing helps children learn math:

How does gesturing help children learn? Gesturing might encourage children to extract meaning implicit in their hand movements. If so, children should be sensitive to the particular movements they produce and learn accordingly. Alternatively, all that may matter is that children move their hands. If so, they should learn regardless of which movements they produce. To investigate these alternatives, we manipulated gesturing during a math lesson. We found that children required to produce correct gestures learned more than children required to produce partially correct gestures, who learned more than children required to produce no gestures. This effect was mediated by whether children took information conveyed solely in their gestures and added it to their speech. The findings suggest that body movements are involved not only in processing old ideas, but also in creating new ones. We may be able to lay foundations for new knowledge simply by telling learners how to move their hands.

Rehab, neuroscience, and religion

Jim Schnabel offers a brief essay in NatureNews on neuroscientists who are suggesting that is effectiveness of drug intervention programs is related to their strengthening of executive frontal lobe functions. Here are a few clips:

The modern addiction rehabilitation industry...even today is dominated by Wilson's Alcoholics Anonymous (AA) paradigm and its 'twelve-step' approach to recovery. Perhaps unsurprisingly, given its spiritual origins, this approach has had an uneasy relationship with the evidence-based culture of medical research. Both perceive addiction as a chronic disease; but whereas scientists seek rationally targeted interventions to blunt drug cravings, AA and related programmes tend to feature group therapy, tearful confessions and the call to "surrender to a higher power"...In the past few years, however, these two cultures have been finding common ground. Neuroscientists have begun to recognize that some of the most important brain systems impaired in addiction are those in the prefrontal cortex that regulate social cognition, self-monitoring, moral behaviour and other processes that the AA-type approach seems to target....treatment programmes are targeting these systems without necessarily knowing that they are doing it.

Religion has been shown to have a strong inverse association with drug addiction...Michael McCullough, who studies religion and behaviour at the University of Miami in Florida, suggests that when a person commits to any cultural system that regulates behaviour, the psychological effort to conform strengthens the brain systems that mediate self-monitoring and self-control. "What makes religion unique, I think, is that the code of conduct isn't just laid down by your parents or your friends or your principal at school, but ostensibly by the individual who is superintending the Universe, so it has an extra moral force." Some religious rituals, he says, have been shown to provoke enhanced activity in prefrontal regions (see Azari et al.). "It's as if certain forms of prayer and meditation are pinpointing precisely those [prefrontal] areas of the brain that people rely on to control attention, to control negative emotion and resolve mental conflict."

In pursuing other ways to boost prefrontal systems medicines for ADHD seem an obvious place to start. Attention-enhancing drugs such as methyl-phenidate and atomoxetine boost the activity of key receptor systems in the prefrontal cortex, in particular those for noradrenaline and dopamine. ..The National Institute on Drug Abuse has also been supporting studies of cognitive and behavioural strategies, and Volkow says that she is particularly enthusiastic about an approach that involves "real-time fMRI feedback". Developed by researcher and entrepreneur Christopher deCharms earlier this decade, the technique involves placing drug users in an fMRI machine and showing them a symbolic representation — a flame — of the fMRI-measured brain activity that corresponds to their cravings. The users are then asked to apply their own cognitive exercises, such as imagining their child is with them, to quench their cravings and douse the flame. After half a dozen sessions with this feedback the user will, in principle, develop cognitive circuitry that is more efficient at suppressing craving and that can then be used in ordinary life. A version of the technique, used for pain relief, has already shown some efficacy in a small clinical trial, and deCharms and his Silicon Valley start-up, Omneuron, are currently running a small trial in smokers — with plans for a follow up with some of Childress's cocaine users.

Negative attitude towards aging when young: decrease in later cardiovascular health.

Levy et al. examine a cohort of 440 individuals drawn from the Baltimore Longitudinal Study of Aging whose attitudes on aging was tested starting in 1968 when they were young (18–49 years, mean age = 36.5 years) and then noted cardiovascular events (89 total, including angina attacks, congestive heart failures, myocardial infarctions, strokes, and transient ischemic attacks) until 2007. 30 years after participants had responded to the age stereotype measure 25% of those with negative-age-stereotypes had experienced a cardiovascular event, compared to 13% who had positive-age-stereotypes.


Association between age stereotypes and time until experiencing a first cardiovascular (CV) event. The graph shows the percentage of participants who had not experienced a CV event as a function of time in each age-stereotype group.

Mental fatigue impairs our physical performance.

This study by Marcora et al. compared subjects who first either watched a movie for 90 min., or did computer exercises requiring concentration, memory and reaction speed - following which all exercised on a stationary bicycle until they were exhausted — that is, unable to maintain a cadence of 60 revolutions per minute. There were no significant differences in physiological measures (heart rate, cardiac output and others) under the two conditions, but bicyclers consistently tired about 15 percent more quickly after the mental exercise than after watching the movies. Apparently their poorer exercise results after mental effort were not caused by reduced performance of their bodies, but because mental fatigue limits exercise tolerance through higher perception of effort.

The Ricky Gervais Show on the "I-Illusion"

Thanks to my son Jon for pointing me to this humorous video.

Neural correlates of religious belief - neuroscience and spirituality

I'm realizing that I have a sufficient number of notes from this area in my queue that I'm not going to get to them separately. So, here I pass on first some links to recent publications and then some work on neural correlates of religious belief.

First, three publications:

"How God changes your brain"

"Contemplative Science: Where Buddhism and Neuroscience Converge"

A conference on Neuroscience and spiritual practices

Next,
Kapogiannis and collaborators attempt to model the complexity of religious belief and then provide brain imaging data correlate their categories with well known brain networks:

We propose an integrative cognitive neuroscience framework for understanding the cognitive and neural foundations of religious belief. Our analysis reveals 3 principle psychological dimensions of religious belief (God's perceived level of involvement, God's perceived emotion, and doctrinal/experiential religious knowledge), which functional MRI localizes within networks processing Theory of Mind regarding intent and emotion, abstract semantics, and imagery. Our results are unique in demonstrating that specific components of religious belief are mediated by well-known brain networks, and support contemporary psychological theories that ground religious belief within evolutionary adaptive cognitive functions.

In a less ambitious effort, Inzlicht et al. suggest that religious people are more chilled out when they commit errors, reflected by reduced reactivity of their anterior cingulate cortex:

Many people derive peace of mind and purpose in life from their belief in God. For others, however, religion provides unsatisfying answers. Are there brain differences between believers and nonbelievers? Here we show that religious conviction is marked by reduced reactivity in the anterior cingulate cortex (ACC), a cortical system that is involved in the experience of anxiety and is important for self-regulation. In two studies, we recorded electroencephalographic neural reactivity in the ACC as participants completed a Stroop task. Results showed that stronger religious zeal and greater belief in God were associated with less firing of the ACC in response to error and with commission of fewer errors. These correlations remained strong even after we controlled for personality and cognitive ability. These results suggest that religious conviction provides a framework for understanding and acting within one's environment, thereby acting as a buffer against anxiety and minimizing the experience of error.

To be less helpful to others, watch violent media...

A sobering study from Bushman and Anderson:

Two studies tested the hypothesis that exposure to violent media reduces aid offered to people in pain. In the first study, participants played a violent or nonviolent video game for 20 min. After game play, while completing a lengthy questionnaire, they heard a loud fight, in which one person was injured, outside the lab. Participants who played violent games took longer to help the injured victim, rated the fight as less serious, and were less likely to "hear" the fight in comparison to participants who played nonviolent games. In the second study, violent- and nonviolent-movie attendees witnessed a young woman with an injured ankle struggle to pick up her crutches outside the theater either before or after the movie. Participants who had just watched a violent movie took longer to help than participants in the other three conditions. The findings from both studies suggest that violent media make people numb to the pain and suffering of others.

How to enhance the wisdom of one...

The point of James Surowiecki's engaging book, "The Wisdom of Crowds" is that a marketplace - of ideas, goods, services, whatever - can make astonishingly accurate predictions of election outcomes, Oscar winners, etc. Herzog and Hertwig ask how a single individual might improve a best guess for an outcome and test a Hegelian process they call "dialectical bootstrapping." After making the first estimate, consider the reasons and assumptions underpinning that estimate (and how they might be off target), and then formulate a new, second estimate that harks back to somewhat different knowledge.

They tested the efficacy of this method by asking 101 students at the University of Basel to date a collection of 40 historical events (e.g., the discovery of electricity), 10 each from the 16th, 17th, 18th, and 19th centuries. Each participant was randomly assigned to one of two conditions. In both conditions, participants first generated their estimates without knowing that they would be asked later to generate a second estimate. In the dialectical-bootstrapping condition, participants (n= 50) were then asked to give dialectical estimates (while their first estimates were displayed in front of them) using a technique inspired by the consider-the-opposite strategy: First, assume that your first estimate is off the mark. Second, think about a few reasons why that could be. Which assumptions and considerations could have been wrong? Third, what do these new considerations imply? Was the first estimate rather too high or too low? Fourth, based on this new perspective, make a second, alternative estimate.

They found that the improvement in accuracy (in years) over the first estimate was twice as large for the dialectical average than for the repeat average, although averaging the first estimates from two random individuals worked better still.

Roots of our social glue

Angier does a nice summary of ideas in Hrdy's forthcoming new book “Mothers and Others: The Evolutionary Origins of Mutual Understanding,” (Harvard Univ. Press):

...the extraordinary social skills of an infant are at the heart of what makes us human. Through its ability to solicit and secure the attentive care not just of its mother but of many others in its sensory purview, a baby promotes many of the behaviors and emotions that we prize in ourselves and that often distinguish us from other animals, including a willingness to share, to cooperate with strangers, to relax one’s guard...Our capacity to cooperate in groups, to empathize with others and to wonder what others are thinking and feeling...probably arose in response to the selective pressures of being in a cooperatively breeding social group, and the need to trust and rely on others and be deemed trustworthy and reliable in turn. Babies became adorable and keen to make connections with every passing adult gaze....mother chimpanzees and gorillas jealously hold on to their infants for the first six months or more of life. Other females may express real interest in the newborn, but the mother does not let go: you never know when one of those females will turn infanticidal, or be unwilling or unable to defend the young ape against an infanticidal male.

Dr. Hrdy wrote her book in part to counter what she sees as the reigning dogma among evolutionary scholars that humans evolved their extreme sociality and cooperative behavior to better compete with other humans. “I’m not comfortable accepting this idea that the origins of hypersociality can be found in warfare, or that in-group amity arose in the interest of out-group enmity,” she said in a telephone interview. Sure, humans have been notably violent and militaristic for the last 12,000 or so years, she said, when hunter-gatherers started settling down and defending territories, and populations started getting seriously dense. But before then? There weren’t enough people around to wage wars. By the latest estimates, the average population size during the hundreds of thousands of years of human evolution that preceded the Neolithic Age may have been around 2,000 breeding adults. “What would humans have been fighting over?” Dr. Hrdy said. “They were too busy trying to keep themselves and their children alive.”

Dr. Hrdy also argues that our human ancestors became emotionally modern long before the human brain had reached its current average volume of 1,300 cubic centimeters, which is about three times the size of a chimpanzee brain — in other words, that we became the nicest apes before becoming the smartest. You don’t need a bulging brain to evolve cooperative breeding. Many species of birds breed cooperatively, as do lions, rats, meerkats, wolves and marmosets, among others. But to become a cooperatively breeding ape, and to persuade a bunch of smart, hot-tempered, suspicious, politically cunning primates to start sharing child care and provisionings, now that took a novel evolutionary development, the advent of this thing called trust.

The Myth of Language Universals

To continue the thread from several previous posts, I pass on the abstract of a draft article by Evans and Levinson titled "The Myth of Language Universals: Language diversity and its importance for cognitive science" :

Talk of linguistic universals has given cognitive scientists the impression that languages are all built to a common pattern. In fact, there are vanishingly few universals of language in the direct sense that all languages exhibit them. Instead, diversity can be found at almost every level of linguistic organization. This fundamentally changes the object of enquiry from a cognitive science perspective.

The article summarizes decades of cross-linguistic work by typologists and descriptive linguists, showing just how few and unprofound the universal characteristics of language are, once we honestly confront the diversity offered to us by the world's 6-8000 languages. After surveying the various uses of 'universal', we illustrate the ways languages vary radically in sound, meaning, and syntactic organization, then examine in more detail the core grammatical machinery of recursion, constituency, and grammatical relations. While there are significant recurrent patterns in organization, these are better explained as stable engineering solutions satisfying multiple design constraints,reflecting both cultural-historical factors and the constraints of human cognition.

Linguistic diversity then becomes the crucial datum for cognitive science: we are the only species with a communication system which is fundamentally variable at all levels. Recognising the true extent of structural diversity in human language opens up exciting new research directions for cognitive scientists, offering thousands of different natural experiments given by different languages, with new opportunities for dialogue with biological paradigms concerned with change and diversity, and confronting us with the extraordinary plasticity of the highest human skills.

MindBlog's winter office...

Inspired by 'the view from your window' feature of Andrew Sullivan's Blog, I thought I would post an iPhone photo of where I am sitting (in Fort Lauderdale, Florida) as I bang out MindBlog's posts. I will be heading back to Madison Wisconsin in early April.

How to keep from stumbling on steps...

Elliott et al. make the neat observation that a simple visual illusion can lead to safer stepping behavior. The perceived height of a step is manipulated as shown in this figure:

Subjects perceived the step to be higher in the V (vertical stripes on the height dimension) configuration on the right compared to the H (horizontal stripes) configuration on the left, and correspondingly raised their toes higher to clear the step.

Neuroscience and the soul.

A recent letter from Martha Farah to Science Magazine is worth passing on:

Science and religion have had a long relationship, by turns collegial and adversarial. In the 17th century Galileo ran afoul of the Church's geocentrism, and in the 19th century Darwin challenged the biblical account of creation. The breaches that open at such times often close again, as religions determine that the doctrine in question is not an essential part of faith. This is precisely what happened with geocentrism and, outside of certain American fundamentalist Christian sects, evolution.

A new challenge to the science-religion relationship is currently at hand. We hope that, with careful consideration by scientists and theologians, it will not become the latest front in what some have called the "culture war" between science and religion. The challenge comes from neuroscience and concerns our understanding of human nature.

Most religions endorse the idea of a soul (or spirit) that is distinct from the physical body. Yet as neuroscience advances, it increasingly seems that all aspects of a person can be explained by the functioning of a material system. This first became clear in the realms of motor control and perception. Yet, models of perceptual and motor capacities such as color vision and gait do not directly threaten the idea of the soul. You can still believe in what Gilbert Ryle called "the ghost in the machine" and simply conclude that color vision and gait are features of the machine rather than the ghost.

However, as neuroscience begins to reveal the mechanisms underlying personality, love, morality, and spirituality, the idea of a ghost in the machine becomes strained. Brain imaging indicates that all of these traits have physical correlates in brain function. Furthermore, pharmacologic influences on these traits, as well as the effects of localized stimulation or damage, demonstrate that the brain processes in question are not mere correlates but are the physical bases of these central aspects of our personhood. If these aspects of the person are all features of the machine, why have a ghost at all?

By raising questions like this, it seems likely that neuroscience will pose a far more fundamental challenge than evolutionary biology to many religions. Predictably, then, some theologians and even neuroscientists are resisting the implications of modern cognitive and affective neuroscience. "Nonmaterialist neuroscience" has joined "intelligent design" as an alternative interpretation of scientific data. This work is counterproductive, however, in that it ignores what most scholars of the Hebrew and Christian scriptures now understand about biblical views of human nature. These views were physicalist, and body-soul dualism entered Christian thought around a century after Jesus' day.

To be sure, dualism is intuitively compelling. Yet science often requires us to reject otherwise plausible beliefs in the face of evidence to the contrary. A full understanding of why Earth orbits the Sun (as a consequence of the way the solar system was formed) took another century after Galileo's time to develop. It may take even longer to understand why certain material systems give rise to consciousness. In the meantime, just as Galileo's view of Earth in the heavens did not render our world any less precious or beautiful, neither does the physicalism of neuroscience detract from the value or meaning of human life.

Saving the world...

A University of Vermont course in the spring of 2008 came up with a magnum opus now published in the Proceedings of the National Academy titled "Overcoming systemic roadblocks to sustainability: The evolutionary redesign of worldviews, institutions, and technologies." I totally have a mind-numbing headache from reading this ponderous but worthwhile effort, and give you a few clips from their summary of "an integrated set of worldviews, institutions, and technologies to stimulate and seed evolutionary redesign of the current socio-ecological regime to achieve global sustainability":

Redefine Well-Being Metrics.
In any new context, we first have to remember that the goal of an economy is to sustainably improve human well-being and quality of life. Material consumption and GDP are merely means to that end, not ends in themselves. We have to recognize, as both ancient wisdom and new psychological research tell us, that material consumption beyond real need can actually reduce overall well-being.
Ensure the Well-Being of Populations During the Transition.
We must ensure that reductions in economic output and consumption fall on those with the lowest marginal utility of consumption, the wealthy. Presently, the U.S. tax code taxes the third wealthiest man in the world, Warren Buffett, at 17.7%, while his receptionist is taxed at the average rate of 30%....although qualitative development may continue indefinitely... existing levels of physical economic output and consumption are already unsustainable and should be reduced.
Reduce Complexity and Increase Resilience.
Efforts to create new cultural/institutional variants can benefit from the lessons offered by history, particularly cases of successful adaptation...Although environmental factors contribute to decline, equally important are the decisions made during the crises. A society's responses depend on the ability of its political, economic, and social institutions to respond, as well as on its cultural values.
Expand the “Commons Sector.”
Recognizing that we are in a biophysical crisis because of our over-consumption and lack of protection of ecosystem services, we must invest in institutions and the technologies required to reduce the impact of the market economy and to preserve and protect public goods. It is now time to create another major category of institution, the commons sector, which would be responsible for managing existing common assets and for creating new ones. Some assets should be held in common because it is more just; these include resources created by nature or by society as a whole.
Remove Barriers to Improving Knowledge and Technology.
With the invention of television, political advertisements became a critical outlet for candidates to broadcast their message and to sway voters. However, the decentralized nature of the Internet allows citizens to gain knowledge about what is done in their name, just as politicians can find out more about those they claim to represent. As a means of two-way communication, the Internet provides voters the ability to speak out within their government without leaving their homes. For the Internet to transform the idea of electronic democracy, universal access is critical. Currently technological, financial, and social barriers exist to such universal accessibility. Removal of these barriers thus becomes a major goal for replacement of the current plutocracy with real democracy.

Persistent effect of early abuse or deprivation on immune function in humans.

The wisconsin group that has studied various aspect of early abuse and deprivation in children offers evidence that adult immune function is compromised in these children, even if they were adopted into nuturing families and more benevolent settings.

It is well known that children need solicitous parenting and a nurturing rearing environment to ensure their normal behavioral development. Early adversity often negatively impacts emotional and mental well-being, but it is less clearly established how much the maturation and regulation of physiological systems is also compromised. The following research investigated the effect of 2 different types of adverse childhood experiences, early deprivation through institutionalization and physical abuse, on a previously unexplored outcome: the containment of herpes simplex virus (HSV). The presence of HSV-specific antibody in salivary specimens was determined in 155 adolescents, including 41 postinstitutionalized, 34 physically-abused, and 80 demographically-similar control youth. Across 4 school and home days, HSV antibody was higher in both postinstitutionalized and physically-abused adolescents when compared with control participants. Because the prevalence of HSV infection was similar across the groups, the elevated antibody was likely indicative of viral recrudescence from latency. Total secretory Ig-A secretion was associated with HSV, but did not account for the group differences in HSV-specific antibody. These findings are likely caused by a failure of cellular immune processes to limit viral reactivation, indicating a persistent effect of early rearing on immune functioning. The fact that antibody profiles were still altered years after adoption into a more benevolent setting with supportive families suggests these results were not caused by contemporaneous factors, but rather reflect a lingering influence of earlier life experiences.

From oral to moral

An interesting synthesis from Chapman et al.

In common parlance, moral transgressions "leave a bad taste in the mouth." This metaphor implies a link between moral disgust and more primitive forms of disgust related to toxicity and disease, yet convincing evidence for this relationship is still lacking. We tested directly the primitive oral origins of moral disgust by searching for similarity in the facial motor activity evoked by gustatory distaste (elicited by unpleasant tastes), basic disgust (elicited by photographs of contaminants), and moral disgust (elicited by unfair treatment in an economic game). We found that all three states evoked activation of the levator labii muscle region of the face, characteristic of an oralnasal rejection response. These results suggest that immorality elicits the same disgust as disease vectors and bad tastes.

A summary graphic from the review of this work by Rozin et al. and some of their comments:

Domains of disgust. The schematic represents routes by which eliciting situations may trigger the disgust output program. Those that run through the disgust evaluation system--which includes appraisal of the elicitor, feelings, and contamination ideation--trigger the full disgust emotion. Solid lines represent routes through which an elicitor can activate the disgust evaluation-output program. Dashed lines (green) represent direct elicitation of the disgust output program. The dotted line (brown) represents a metaphoric, indirect route.

According to the principle of preadaptation, a system that evolves for one purpose is later used for another purpose. From this viewpoint, disgust originates in the mammalian bitter taste rejection system, which directly activates a disgust output system. This primal route (e.g., bitter and some other tastes) evokes only the output program, without a disgust evaluation phase. During human evolution, the disgust output system was harnessed to a disgust evaluation system that responded not to simple sensory inputs (such as bitter tastes) but to more cognitively elaborated appraisals (e.g., a cockroach). Initially, the evaluation system was a food rejection system that rejected potential foods on the basis of their nature or perceived origin. This was the first "true disgust," because it engaged this evaluation system. Later, through some combination of biological and cultural evolution, the eliciting category was enlarged to include reminders of our animal nature, as wel as some people or social groups. This process had adaptive value, because by making things or thoughts disgusting a culture could communicate their negativity and cause withdrawal from them.