Certain recurring themes have emerged from research on intelligent behavior from literatures as diverse as developmental psychology, artificial intelligence, human reasoning and problem solving, and primatology. These themes include the importance of sensitivity to goal structure rather than action sequences in intelligent learning, the capacity to construct and manipulate hierarchically embedded mental representations, and a troubling domain specificity in the manifestation of each.

Seen in its historical context, Mazur & Booth's (M&B's) target article may come to be viewed as a turning point in the study of the biological basis of human behavior in general, and dominance in particular. To facilitate further research, suggestions are offered for making the definition of dominance more precise. From an evolutionary point of view, the testosterone-dominance link may be as important in women as it is in men.

We cannot solve questions about imitative learning without knowing what motivates animals to copy others. Imitative capacities can be expected to be most pronounced in relation to situations and models of great social significance. Experimental research on nonhuman primates has thus far made little effort to present such situations and models.

Our commentary summarises the current understanding of how testosterone can be used as a mechanism to link quality to external traits potentially used in sexual signalling, particularly female choice. Testosterone-dependent traits may reveal male's status to rivals and immunocompetence to females. We highlight some interesting unanswered questions and suggest that cross-disciplinary collaboration would help solve them.

Millikan contrasts her substance-based view of concepts with “descriptionism” according to which description determines what falls under a concept. Focusing on her discussion of the role of language in the acquisition of concepts, I argue that descriptions cannot be separated from perception in the ways Millikan's view requires.

Differences and similarities between modal and amodal completions can only be understood by considering the goals of visual completion: unity, shape, and perceptual quality. Pessoa et al. cannot reject representational accounts of vision because of flaws with isomorphic representations of perceptual quality: representations and processes for perceptual quality (modal completion) and most likely dissociable from those for unity and shape (nonmodal completions).

This commentary advocates an alternative to null-hypothesis testing that was originally represented by Rozeboom over three decades ago yet is not considered by Chow (1996). The central distinguishing feature of this approach is that it allows the scientist to conclude that the data are much better fit by those hypotheses whose values fall inside the interval than by those outside.

Many animals, including dogs, produce vocal signals in which their mouths open and close producing “syllables.” In contrast, the vocal signals of species other than humans are tied to emotional states. The Broca's-Wernicke's area model of the brain bases of language is wrong.

To explore the neural mechanisms engaged by the perception of action with the intent to imitate, positron emission tomographic activation studies were performed in healthy human subjects. We discuss the results in light of the framework proposed by Byrne & Russon, especially the distinction between mechanisms subserving action-level and program-level imitation.

Entertaining diverse assumptions about empirical research, commentators give a wide range of verdicts on the NHSTP defence in Statistical significance. The null-hypothesis significance-test procedure (NHSTP) is defended in a framework in which deductive and inductive rules are deployed in theory corroboration in the spirit of Popper's Conjectures and refutations (1968b). The defensible hypothetico-deductive structure of the framework is used to make explicit the distinctions between (1) substantive and statistical hypotheses, (2) statistical alternative and conceptual alternative hypotheses, and (3) making statistical decisions and drawing theoretical conclusions. These distinctions make it easier to show that (1) H0 can be true, (2) the effect size is irrelevant to theory corroboration, and (3) “strong” hypotheses make no difference to NHSTP. Reservations about statistical power, meta-analysis, and the Bayesian approach are still warranted.

There is substantial evidence that psychological factors influence human testosterone levels, but little support if any for an influence of circulating testosterone on dominance in men. Persistent interest in testosterone as an explanation of behaviors such as dominance and aggression might reflect the influence of cognitive schemas regarding race and sex rather than empirical evidence.

Millikan's account of how we acquire our most basic concepts might be clarified by a better ontological taxonomy, especially one that distinguishes between natural kinds on the one hand and wholes composed of parts on the other. The two have a different causal basis, which is important because once classification goes beyond the stage of naive induction, it becomes fundamentally etiological.

The following points are discussed in response to the commentaries: (1) A taxonomy of perceptual completion phenomena should rely on both phenomenological and mechanistic criteria. (2) Certain forms of perceptual completion are caused by topographically organized neural processes – neural filling-in. (3) The bridge locus, understood as the final site of perceptual experience in the brain, should be replaced by the principle that each token percept has a neural substrate that is nomically sufficient for it, all else being equal. (4) Analytic isomorphism – the view that there must be a pictorial or spatial neural-perceptual isomorphism at the bridge locus – should be rejected. Although more abstract kinds of isomorphism are central to the neural-perceptual mapping, the perceptual cannot be exhaustively explained in terms of the neural, and therefore the explanation of perception cannot be reduced to uncovering neural-perceptual isomorphisms. (5) The task of vision is to guide action in the world, not to construct a detailed world-model in the head. (6) Neural filling-in facilitates the integration of information and thereby helps the animal find out about its environment. (7) Perceptual content needs to be understood at the level of the person or animal interacting in the world.

It is likely that the system controlling speech has evolved from the one that controls feeding. However, the idea that frames and content are programmed independently by two different cortical areas is not plausible. Models of the speech control system must also take into account the need to coordinate the respiratory, laryngeal, and articulatory musculature.

Byrne & Russon argue that the action and program levels of imitation form two discrete categories, with no intermediate steps. A Piagetian view enlarges our understanding of human and ape imitation by showing the developmental paths that imitation takes in the sensory-motor period of intelligence. It is clear from Piaget's (1945/1962) analysis that the action level of imitation is richly varied and that intermediate steps do occur between the action and program levels.

Neuroethological investigations of mammalian and avian auditory systems have documented species-specific specializations for processing complex acoustic signals that could, if viewed in abstract terms, have an intriguing and striking relevance for human speech sound categorization and representation. Each species forms biologically relevant categories based on combinatorial analysis of information-bearing parameters within the complex input signal. This target article uses known neural models from the mustached bat and barn owl to develop, by analogy, a conceptualization of human processing of consonant plus vowel sequences that offers a partial solution to the noninvariance dilemma – the nontransparent relationship between the acoustic waveform and the phonetic segment. Critical input sound parameters used to establish species-specific categories in the mustached bat and barn owl exhibit high correlation and linearity due to physical laws. A cue long known to be relevant to the perception of stop place of articulation is the second formant (F2) transition. This article describes an empirical phenomenon – the locus equations – that describes the relationship between the F2 of a vowel and the F2 measured at the onset of a consonant-vowel (CV) transition. These variables, F2 onset and F2 vowel within a given place category, are consistently and robustly linearly correlated across diverse speakers and languages, and even under perturbation conditions as imposed by bite blocks. A functional role for this category-level extreme correlation and linearity (the “orderly output constraint”) is hypothesized based on the notion of an evolutionarily conserved auditory-processing strategy. High correlation and linearity between critical parameters in the speech signal that help to cue place of articulation categories might have evolved to satisfy a preadaptation by mammalian auditory systems for representing tightly correlated, linearly related components of acoustic signals.

Externalism cannot work as a theory of concepts without explaining how we reidentify substances as being of the same kind. Yet this process implies just the level of descriptive content to which externalism seeks to deny a role in conceptual content.

The frame/content theory justifiably makes tinkering an important explanatory principle. However, tinkering is linked to the accidental and, if completely decoupled from functional constraints, it could potentially play the role of an “idiosyncracy generator,” thus offering a sort of “evolutionary” alibi for the Chomskyan paradigm – the approach to language that MacNeilage most emphatically rejects. To block that line of reasoning, it should be made clear that evolutionary opportunism always operates within the constraints of selection.

(1) Mazur & Booth do not explain precontest rise in testosterone. Anticipatory T rise may result from fantasized dominance scenarios. (2) Mazur & Booth conclude that females do not experience the dominance–T rise effect. The data are insufficient for this judgment. (3) Mazur & Booth misstate my position on T and sexuality. I offer an emendation and correction.

Working memory limits are best defined in terms of the complexity of the relations that can be processed in parallel. Complexity is defined as the number of related dimensions or sources of variation. A unary relation has one argument and one source of variation; its argument can be instantiated in only one way at a time. A binary relation has two arguments, two sources of variation, and two instantiations, and so on. Dimensionality is related to the number of chunks, because both attributes on dimensions and chunks are independent units of information of arbitrary size. Studies of working memory limits suggest that there is a soft limit corresponding to the parallel processing of one quaternary relation. More complex concepts are processed by “segmentation” or “conceptual chunking.” In segmentation, tasks are broken into components that do not exceed processing capacity and can be processed serially. In conceptual chunking, representations are “collapsed” to reduce their dimensionality and hence their processing load, but at the cost of making some relational information inaccessible. Neural net models of relational representations show that relations with more arguments have a higher computational cost that coincides with experimental findings on higher processing loads in humans. Relational complexity is related to processing load in reasoning and sentence comprehension and can distinguish between the capacities of higher species. The complexity of relations processed by children increases with age. Implications for neural net models and theories of cognition and cognitive development are discussed.