the target article proposes that behavioral asymmetries evolved in response to social pressures, accounting for the unequal distribution of handedness across the population. in contrast, we provide evidence that human handedness reflects individual adaptations that enhance movement skill, and that the distribution across the population is best explained by a genetic polymorphism, either balanced or tending toward fixation for right-handedness.

Ainslie's insightful treatment of dynamically inconsistent choice stands in contrast to traditional views in psychology, economics, and philosophy. We comment on the form of the discounting function and on new findings regarding choice between delayed rewards. Finally, we argue that the positive correlation between temporal and probability discounting is inconsistent with the view that impulsivity represents a unitary trait.

Dichotomizing perceptions, by those that have an objective reality and those that do not, is rejected. Perceptions are suggested to fall along a multidimensional continuum in which neither end is totally “pure.” At the extreme ends, perceptions neither have an objective reality without some subjectivity, nor, at the other end, even as hallucinations, are they totally dissociated from reality.

Sign languages exhibit all the complexities and evolutionary advantages of spoken languages. Consequently, sign languages are problematic for a theory of language evolution that assumes a gestural origin. There are no compelling arguments why the expanding spiral between protosign and protospeech proposed by Arbib would not have resulted in the evolutionary dominance of sign over speech.

Depue & Morrone-Strupinsky’s (D&M-S’s) language suggests that, unlike Kent Berridge, they may allow that the activity of a largely subcortical system, which is presumably often introspectively and cognitively inaccessible, constitutes affectively felt experience even when so. Such experience would then be phenomenally conscious without being reflexively conscious or cognitively access-conscious, to use distinctions formulated by the philosopher Ned Block.

notwithstanding the many strengths of the dynamic developmental theory, there remain challenges to be overcome before it can be incorporated into a true causal model of attention-deficit/hyperactivity disorder (adhd). these include the development of reliable measures of reinforcement delay gradients, the validation of shortened reinforcement delay as an endophenotype, and the integration of this pathway with other potential pathways.

Arbib offers a comprehensive, elegant formulation of brain/language evolution; with significant implications for social as well as biological sciences. Important psychological antecedents and later correlates are presupposed; their conceptual enrichment through protosign and protospeech is abbreviated in favor of practical communication. What culture “is” and whether protosign and protospeech involve a protoculture are not considered. Arbib also avoids dealing with the question of evolution of mind, consciousness, and self.

When viewed from a distance, visual hallucinations fall into one of two symptom patterns, a dichotomy which poses a problem for theoretical models treating them as a single entity. Such models should be broadened to allow for two distinct but overlapping syndromes – one likely to relate to visual de-afferentation, the other to Perception and Attention Deficit (PAD) cholinergic pathology.

The idea of “bundling” lesser later rewards so they outweigh smaller sooner rewards is compelling, but the sophisticated cognitive activity involved in this bundling is not yet modeled; in particular the role of language is hard to assess.

despite general agreement that altered reward sensitivity is involved in attention-deficit/hyperactivity disorder (adhd), a wide range of different alterations has been proposed. we cite work showing abnormal sensitivity to delay of reward, together with abnormal sensitivity to individual instances of reward. we argue that at the cellular level these behavioural characteristics might indicate that dopamine timing is off in children with adhd.

In general, we agree with Pothos's claim that similarity and rule knowledge are best viewed as situated on the extreme points of a single representational continuum. However, we contend that a distinction can be made between “rule-like” and “rule-based” knowledge: Rule-based, symbolic knowledge is necessarily conscious when it is applied. Awareness thus provides a useful criterion for distinguishing between sensitivity to functional similarity and knowledge of symbolic rules.

Evidence from aphasia is considered that leads to a distinction between abstract and concrete thought processes and hence for a distinction between rules and similarity. It is argued that perceptual classification is inherently a rule-following procedure and these rules are unable to be followed when a patient has difficulty with name comprehension and retrieval.

This commentary takes a closer look at how “constructive models of subjective perception,” referred to by Collerton et al. (sect. 2), might contribute to the Perception and Attention Deficit (PAD) model. It focuses on the neuronal mechanisms that could mediate hallucinations, or false inference – in particular, the role of cholinergic systems in encoding uncertainty in the context of hierarchical Bayesian models of perceptual inference (Friston 2002b; Yu & Dayan 2002).

Miller and Rodgers (2001) proposed a central nervous system based Ontogenetic Bonding System that operates across the life course to promote succorant, affiliative, sexual, and nurturant bonds. I discuss features of this theoretical framework that can inform Depue & Morrone- Strupinsky’s (D&M-S’s) model. Most important, I suggest that the affiliative reward processes D&M-S describe are better conceptualized as subserving the affect/motivation of affection.

commentary on our target article centers around six main topics: (1) strategies in modeling the neurobehavioral foundation of human behavioral traits; (2) clarification of the construct of affiliation; (3) developmental aspects of affiliative bonding; (4) modeling disorders of affiliative reward; (5) serotonin and affiliative behavior; and (6) neural considerations. after an initial important research update in section r1, our response is organized around these topics in the following six sections, r2 to r7.

Explaining the transition from a signed to a spoken protolanguage is a major problem for all gestural theories. I suggest that Arbib's improved “beyond the mirror” hypothesis still leaves this core problem unsolved, and that Darwin's model of musical protolanguage provides a more compelling solution. Second, although I support Arbib's analytic theory of language origin, his claim that this transition is purely cultural seems unlikely, given its early, robust development in children.

We question the behavioral premise underlying Ainslie's claims about hyperbolic discounting theory. The alleged evidence for humans can be easily explained as an artefact of experimental procedures that do not control for the credibility of payment over different time horizons. In appropriately controlled and financially motivated settings, human behavior is consistent with conventional exponential preferences.

In offering a detailed view of putative steps towards the emergence of language from a cognitive standpoint, Michael Arbib is also introducing an evolutionary framework that can be used as a useful tool to confront other viewpoints on language evolution, including hypotheses that emphasize possible alternatives to suggestions that language could not have emerged from an earlier primate vocal communication system.

There are strong resemblances between the neurobiological characteristics of hallucinations occurring in the particular case of schizophrenia and the hallucinatory activity observed during the rapid-eye-movement (dreaming) sleep stage: the same prefrontal dorsolateral deactivation; forebrain disconnectivity and disinhibition; sensory deprivation; and acetylcholine, monoamine, and glutamate modifications.

A qualitative difference between Rules and Similarity in categorization can be described in terms of “commitment”: Rules entail it, Similarity does not. Commitment derives from people's knowledge of a domain, and it is what justifies people's inferences, selective attention, and dismissal of irrelevant information. Studies show that when children have knowledge, they manifest these aspects of commitment, thus overcoming Similarity.