On becoming cultural - models for evolution of human behavior

Ruth Mace describes articles by Bowles and by Powell et al. on the origins of altruism toward one's own social group and the emergence of cultural complexity. They invoke evolution and selection of behavioral traits at the level of groups, a topic I've mentioned in numerous previous posts (enter 'group selection' in the search box at left to review them). Clips from Mace's review:

...Genetic and cultural traits are both heritable and subject to evolutionary processes, but cultural traits are not transmitted in a Mendelian way; they can be inherited from almost anyone, including people who may not share your genetic interests...Perhaps the central difference between genetic and cultural transmission is that we can change our cultural phenotype during our lives—for example, to conform to group norms. Cultural differences between groups might be easier to maintain than are genetic ones, due to processes such as conformist social learning and punishment; several models show that if these processes occur, cultural group selection could explain the evolution of prosocial or altruistic behavior.

In what is essentially an extension of the Baldwin Hypothesis (again, check the blog's search box) Bowles makes the claim that:

...the demographic structure of hunter-gatherer populations allowed group-selected genetic traits to evolve in humans. He argues that lethal warfare was endemic and that altruistic, group-beneficial behaviors that hurt the survival chances of individuals but improved the likelihood for groups to win conflicts could emerge by group selection. This argument was originally espoused by Darwin, but few formal tests of it have been done.

In his model, Bowles identifies two key determinants of whether group selection can favor altruistic behavior: the individual and group costs and benefits of altruism in warfare, and the extent of genetic differentiation among groups. An array of ethnographic and archaeological evidence shows that hunter-gatherers certainly did kill each other. How much of this killing was within or between groups is tricky to ascertain (especially from archaeological data) and varies among sites, but on average, 14% of adult deaths appear to have been due to warfare...based on genetic studies of extant hunter-gatherers, the model shows that a realistic level of inbreeding within groups allows group benefits to offset fitness costs of roughly 3% associated with being an "altruistic warrior" relative to nonaltruists. Ironically, lethal hostility toward other groups could thus underpin cooperation and support within human communities.

Powell et al. argue:

...that changes in population size and structure can explain the patterns of acquisition (and loss) of culturally inherited skills (like the ~10,000-40,000 year old harpoon shown) ...[Their model]..examines a structured population, in which individuals live in groups (subpopulations) and inherit (learn) skills from others in the group or by contact due to migration between groups. The results show that the time since first occupation of a region is a far less reliable predictor of the accumulation of cultural skills than is the density of subpopulations and the degree of migration between them.

The two models paint rather different pictures of Pleistocene life. Were early modern humans in frequent contact with neighboring groups to exchange cultural innovations, or were they inward looking, unwilling to travel, and constantly engaging their neighbors in lethal conflict? Probably both, at different times and in different places (although it may be possible to steal someone's cultural innovations and kill them too).

Nonverbal Status Cues Alter Perceived Size

Marsh et al. show that nonverbal cues associated with social dominance also affect the perceived size of the displayer.

Regret in animals

In That Tucked Tail, Real Pangs of Regret?

No evidence for mirror neurons in humans?!

Given all the hype over the mirror neuron system in humans (basis for constructing social cognition, empathy, mind reading, and the development of language, etc. - this blog has mostly joined the chorus) , this recent work by Lingnau would seem to be quite a bombshell. Their introduction explains the logic, context and basic results:

There are 2 conditions that must be fulfilled by any study that aims to address the existence of mirror neurons in humans. First, it must be demonstrated that execution and recognition of a specific motor act activate a common set of neurons in so-called mirror neuron areas (condition I). Importantly, this overlap must be act specific. Second, it must be demonstrated that activation of neurons within potential mirror neuron areas results from direct activation and not from a prior nonmotor categorization on the basis of inferences about potential motor acts from minimal visual cues, e.g., seeing a hand move toward a familiar graspable object, inviting the inference that the actor's intention may be to grasp the object (condition II).

Their study meets these conditions:

We studied within- and cross-modal adaptation for simple intransitive motor acts that are not associated with a particular meaning, such that any observed adaptation effect could not be attributed to adaptation of the same semantic representation or the same object. Furthermore, to ensure that participants would not be able to guess the target motor act from initial features of a movement, we used 8 different unpredictable movements that could be distinguished from each other only at a relatively late phase of the movement.

We found adaptation for executed motor acts, when these were preceded by execution or observation of the same motor act, as would be expected if a previously executed or observed motor act were to prime the subsequent execution of that act. Importantly, we found no sign of adaptation when motor acts were first executed and then observed. ...our data do not support the direct matching account, according to which neurons exist that selectively respond to actions irrespective of whether these are observed or executed. Our data are compatible with the assumption that responses in mirror neuron areas reflect the facilitation of the motor system because of learned associations between semantic representation of actions and their generating motor programs.

Positive and negative emotions bias the earliest stages of our visual processing.

Opposing Influences of Affective State Valence on Visual Cortical Encoding

Hardwired human nature?

David Brooks repeats some of the arguments needed as an antidote to the evolutionary psychology craze that is reinforced by books such as Geoffrey Miller's "The Mating Mind" and more recently, "Spent."

The Stonewall Riots

The Stonewall riots that started on June 27, 1969, have achieved iconic status as the start of my tribe's 'liberation.' Here is an interesting recollection by an observer.

Risky behaviors: genetic predisposition countered by behavioral intervention

Work by Brody et al. is summarized by Jasny in the Editor's Choice section of the June 5 issue of Science:

There have been many discussions of how genes and environment might interact in the context of human behavior. Brody et al. have studied the effects of a randomized behavioral intervention on adolescents who have a genetic polymorphism associated with the initiation of risky behavior. Roughly 600 11-year-olds were randomly assigned to the Strong African American Families (SAAF) program or to a control group. The SAAF group (and their caregivers, usually mothers) participated in separate and joint training sessions on parenting practices, stress management, dealing with racism, setting goals, and norms for the use of alcohol and other substances. Sessions occurred over the course of 1 year, and the initiation of risky behaviors was assessed at the beginning of the program and for the next 2.5 years. Two years later, saliva samples were collected to look for a polymorphism in the promoter region of the serotonin transporter. Possession of a short form of the allele has been associated previously with impulsivity, substance abuse, and early sexual activity. In the control group, adolescents with the short allele were twice as likely to have engaged in risky behaviors as those assigned to the SAAF group or those with the long allele in either group. Only one genetic polymorphism was examined, and the results need to be confirmed in a variety of populations; however, this provides further evidence of the value of this intervention and the mutability of the effects of genetic predisposition.

Pretty Please....

Why are we more friendly towards the pleading behavior of very young humans or animals? The Nature "Research Highlights" section notes a study on the pleading behavior of young meerkats by Madden et al.:

Many young animals beg for food from their elders. But, eventually, the pleading stops or the charity dries up. Joah Madden, at the University of Cambridge, UK, and his team looked to find the biological triggers that put an end to begging behaviour by studying free-ranging meerkats (Suricata suricatta) of the Kalahari Desert in South Africa over an 18-month period.

The group analysed the begging calls of meerkat pups aged between 40 and 60 days — the peak of their begging behaviour — and compared them with the calls of the same individuals aged 100–120 days. Experimental playback to adults revealed that lower-pitched juvenile calls reaped fewer rewards than the pleading of pups.

An evolutionary rationale for blushing.

An article from Benedict Carey covers work suggesting the blushing evolved to to strengthen social bonds.

Gender, culture, and mathematics performance

Janet Hyde at Wisconsin continues her crusade against the proposition that there are gender differences in mathematical performance and talent. (Unfortunate comments on this issue got Larry Summers fired - or more accurately, he 'resigned under pressure' - as Harvard President.)

Unconscious motor control that conflicts with conscious awareness.

During my recent Europe vacation, on stepping onto an escalator in the Munich metro that I knew was stopped, I noticed that odd sensation accompanied by clumsy movements that is probably also familiar to you, as if my motor behavior and sensations were being guided by a “phantom” of a moving escalator. Fukui et al. show that this is the consequence of an unconscious automatic habitual motor program cued by the escalator itself. Their results suggest a dissociation between conscious awareness and subconscious motor control: the former makes us perfectly aware of the current environmental situation, but the latter automatically emerges as a result of highly habituated visual input no matter how unsuitable the motor control is.

Boosting your serotonin reduces responsiveness to aggression

From Berman et al.:

We tested the theory that central serotonin (5-hydroxytryptamine, or 5-HT) activity regulates aggression by modulating response to provocation. Eighty men and women (40 with and 40 without a history of aggression) were randomly assigned to receive either 40 mg of paroxetine (to acutely augment serotonergic activity) or a placebo, administered using double-blind procedures. Aggression was assessed during a competitive reaction time game with a fictitious opponent. Shocks were selected by the participant and opponent before each trial, with the loser on each trial receiving the shock set by the other player. Provocation was manipulated by having the opponent select increasingly intense shocks for the participant and eventually an ostensibly severe shock toward the end of the trials. Aggression was measured by the number of severe shocks set by the participant for the opponent. As predicted, aggressive responding after provocation was attenuated by augmentation of serotonin in individuals with a pronounced history of aggression.

Questioning the link between brain size and sociality

Almost any lecture on brain evolution includes the assertion that larger brains evolved to serve communication demands of larger social groups. Finarelli and Flynn question this for the carnivores (cats, dogs, bears, weasels, and their relatives).

Anticipating monetary and social reward - differing brain activations in men and women.

Spreckelmeyer et al. show a wider network of brain regions is activated by the prospect of monetary reward in men than in women.

Lost in the sauce - alcohol and mind wandering

Great.... all I need is another reason to question the daily happy hour that I use to take the edge off the TV evening news. From Sayette et al:

Alcohol consumption alters consciousness in ways that make drinking both alluring and hazardous. Recent advances in the study of consciousness using a mind-wandering paradigm permit a rigorous examination of the effects of alcohol on experiential consciousness and metaconsciousness. Fifty-four male social drinkers consumed alcohol (0.82 g/kg) or a placebo beverage and then performed a mind-wandering reading task. This task indexed both self-caught and probe-caught zone-outs to distinguish between mind wandering inside and outside of awareness. Compared with participants who drank the placebo, those who drank alcohol were significantly more likely to report that they were zoning out when probed. After this increase in mind wandering was accounted for, alcohol also lowered the probability of catching oneself zoning out. The results suggest that alcohol increases mind wandering while simultaneously reducing the likelihood of noticing one's mind wandering.

Mathematical and linguistic syntax: different brain areas

Contra the suggestion of Hauser, Chomsky, and Fitch that the hierarchical processing required for syntactical operations requires Broca's area, central to language, Friedrich and Friederici find MRI evidence that syntactic processing of abstract mathematical formulae involves mainly intraparietal and prefrontal regions:

Theory predicts a close structural relation of formal languages with natural languages. Both share the aspect of an underlying grammar which either generates (hierarchically) structured expressions or allows us to decide whether a sentence is syntactically correct or not. The advantage of rule-based communication is commonly believed to be its efficiency and effectiveness. A particularly important class of formal languages are those underlying the mathematical syntax. Here we provide brain-imaging evidence that the syntactic processing of abstract mathematical formulae, written in a first order language, is, indeed efficient and effective as a rule-based generation and decision process. However, it is remarkable, that the neural network involved, consisting of intraparietal and prefrontal regions, only involves Broca's area in a surprisingly selective way. This seems to imply that despite structural analogies of common and current formal languages, at the neural level, mathematics and natural language are processed differently, in principal.

Money, social distress, and physical pain

The Symbolic Power of Money: Reminders of Money Alter Social Distress and Physical Pain

Aging, isolation, and internet social networks

An article by Stephanie Clifford on isolated older adults finding social sustenance through internet social sites.

Why we pig out.

Parker-Pope describes how the food industry combines and creates foods in a way that taps into our brain circuitry to stimulate our desire for more.