Chow' efforts toward a methodology of theory-corroboration and the plea for significance testing are welcome, but there are many risky claims. A major omission is a discussion of significance testing in the Bayesian framework. We sketch here the Bayesian reinterpretation of the significance level for assessing direction of effects.

Culture and social structure may affect the testosterone–behavior link by shaping the way we construe events; by muting, channelling, or amplifying the drives that testosterone produces; and by affecting the distribution and level of testosterone in various parts of the population. Research on testosterone, culture, and social class has produced suggestive results, opening broad areas for research.

Findings in dynamic unit formation suggest that completion processes reflect the optics of our world. Dynamic unit formation may depend on patterns of motion signals that are consistent with the causes of optical changes. In addition, dynamic completion conforms to a local curvature minimization constraint. Such relational aspects of vision are important to consider in linking perceptual experience and neural activity.

The jaw movements of speech are most probably derived from jaw movements associated with vocalisation. Cyclicity does not argue strongly for derivation from a cyclic pattern, because it arises readily in any system with feedback control. The appearance of regular repetition as a part of ritualisation of a display may have been important.

Mazur & Booth's target article presents strong evidence that social factors influence testosterone; however, the evidence for an effect of testosterone on dominance is considerably weaker. Although social and biological factors may interact, as suggested in the reciprocal model, findings in rhesus monkeys suggest that social factors may predominate. Finally, research is needed to evaluate whether androgens during early life influence later dominance.

In conformity with the dynamical perspective advocated by van Gelder, a more psychological approach can highlight the intrinsic temporality of human cognition, revealing the inadequacies of representationalism as a framework for the modeling of mind.

Does feature evolution stop once we have acquired sufficient features to perform a recognition task? With extended practice, novices may develop a more sophisticated feature space that allows them to perform more accurately or quickly. Our work on perceptual expertise indicates that feature learning and reorganization can continue even after an initial set of features is available to represent a novel class of objects.

Chow's book provides a thorough analysis of the confusing array of issues surrounding conventional tests of statistical significance. This book should be required reading for behavioral and social scientists. Chow concludes that the null-hypothesis significance-testing procedure (NHSTP) plays a limited, but necessary, role in the experimental sciences. Another possibility is that – owing in part to its metaphorical underpinnings and convoluted logic – the NHSTP is declining in importance in those few sciences in which it ever played a role.

The origin of features from nonfeatural information is a problem that should concern all theories of object categorization and recognition, not just the flexible feature approach. In contrast to the idea that new features must originate from combinations of simpler fixed features, we argue that holistic features can be created from a direct imprinting on the visual medium. Furthermore, featural descriptions can emerge from processes that by themselves do not operate on feature detectors. Once acquired, features can be decomposed into component features if required by other categorizations. We therefore argue that it is not necessary to separate holistic and componential approaches to representations, because the latter is a development of the former. The requirements for representational flexibility outstrip the performance of any existing computational models, but specific mechanisms of feature creation are discussed and evaluated. Challenges for feature creation mechanisms are discussed together with the constraints (perceptual, statistical, functional, and task) they will need to satisfy.

Studies of testosterone's effect on dominance are confounded by the effects of dominance experiences on testosterone. Furthermore, antisocial behavior tends to originate prepubertally, when testosterone levels are the same for aggressive males, nonaggressive males, and females. It seems more parsimonious to view variation in testosterone as an effect of dominance-related mood states than to invoke a reciprocal model.

Chow ably defends classical significance testing by relating this method to venerable principles for inductive reasoning. Chow's success does not preclude the use of other approaches to statistical reasoning, which is fortunate not only for Bayesian rivals, but even for some fellow classicists.

Filled-in sensations exhibit a distinctive mélange of causal features, resembling perceptual sensations in some respects and imagery in others. This commentary identifies several of these shared causal features and advances the hypothesis that filled-in sensations may constitute the primordial species of imagery, the evolutionary neurofunctional precursor of paradigmatic forms of imagery.

Van Gelder's clear distinction between the quantitative nature of dynamical systems and the nonquantitative nature of computational processes provides a firm basis for distinguishing between processes that happen in time and processes that happen over time. Symbolic reasoning, the presumed basis of intelligent behavior in robots, happens over time. However, the movements and actions that robots must make to behave intelligently, happen in time. Attempting to connect the two, as classical artificial intelligence and robotics have presumed to be necessary, has produced a tension and an arbitrarily moving interface in the construction of robots. Adopting a robotic version of the dynamical hypothesis offers sound theoretical and scientific justification for those robotics researchers who continue to insist that getting the interaction dynamics of intelligent behavior right is a purely dynamical matter, and never a symbolic computational one.

MacNeilage's target article develops a theory for the evolution of human speech articulation along the lines of “slot- filler” structure. His content/frame schema commits him to the tenets of embodiment, muscle sense, and a memory for speech. My commentary ties these aspects together in their historical and current perspective.

Cognitive agents are dynamical systems but not quantitative dynamical systems. Quantitative systems are forms of analogue computation, which is physically too unreliable as a basis for cognition. Instead, cognitive agents are dynamical systems that implement discrete forms of computation. Only such a synthesis of discrete computation and dynamical systems can provide the mathematical basis for modeling cognitive behavior.

If syllables are the link between nonhuman calls and human speech, as MacNeilage suggests, then that link is actually revealed in the “syllabic” sounds of the 3-month-old infant, well before the reduplicative babbling of the 8-month-old. Anatomical, acoustic, cognitive, and social perceptual evidence supports this earlier landmark.

We argue that Chow's defense of hypothesis-testing procedures attempts to restore an aura of objectivity to the core procedures, allowing these to take on the role of judgment that should be reserved for the researcher. We provide a brief overview of what we call the historical case against hypothesis testing and argue that the latter has led to a constrained and simplified conception of what passes for theory in psychology.

Concepts are highly theoretical entities. One cannot study them empirically without committing oneself to substantial preliminary assumptions. Among the competing theories of concepts and categorization developed by psychologists in the last thirty years, the implicit theoretical assumption that what falls under a concept is determined by description (“descriptionism”) has never been seriously challenged. I present a nondescriptionist theory of our most basic concepts, “substances,” which include (1) stuffs (gold, milk), (2) real kinds (cat, chair), and (3) individuals (Mama, Bill Clinton, the Empire State Building). On the basis of something important that all three have in common, our earliest and most basic concepts of substances are identical in structure. The membership of the category “cat,” like that of “Mama,” is a natural unit in nature, to which the concept “cat” does something like pointing, and continues to point despite large changes in the properties the thinker represents the unit as having. For example, large changes can occur in the way a child identifies cats and the things it is willing to call “cat” without affecting the extension of its word “cat.” The difficulty is to cash in the metaphor of “pointing” in this context. Having substance concepts need not depend on knowing words, but language interacts with substance concepts, completely transforming the conceptual repertoire. I will discuss how public language plays a crucial role in both the acquisition of substance concepts and their completed structure.

It is fruitful to think of the representational and the organism-centered approaches as complementary levels of analysis, rather than mutually exclusive alternatives. Claims to the contrary by proponents of the organism-centered approach face what we call the “basketball problem.”

Prenatal exposure to high levels of testosterone may lead to increased probability of left-handedness. Extrapolating from arguments by Mazur & Booth leads to a prediction of increased incidence of antisocial behavior among left-handers. Six hundred ninety-four males were tested for seven indicators of delinquency in high school. Left-handers were more likely to display such behaviors, providing indirect evidence for the hypothesized behavioral effects of testosterone.