Rogers & McClelland (R&M) have provided an impressive outline of the capabilities of a class of multi-layered perceptrons that mimic many aspects of human knowledge acquisition. Despite this success, in the literature several basic issues are raised and concerns are expressed. Indeed, the problems are so acute that a different way of thinking is called for. In this commentary it is suggested that rational models approach provides a promising alternative.

The visual prediction that Nijhawan proposes cannot explain why the flash-lag effect depends on what happens after the flash. Moreover, using a visual prediction based on retinal image motion to compensate for neuronal time delays will seldom be of any use for motor control, because one normally pursues objects with which one intends to interact with ones eyes.

This commentary considers the issues of what should be taken as evidence for semantic categorization in infants and why infants display a surprising asymmetry in the categorization of humans versus nonhuman animals. It is argued that perceptual knowledge should be viewed as a potent source of information for semantic categorization, and that the asymmetrical categorization behavior arises as a consequence of the frequency and similarity structure of experience.

Are the neural systems involved in recognizing affective prosody in language also used for emotion recognition in instrumental music? One way to test this idea is to study musical affect perception in patients with receptive affective aprosodia (RAA). Music perception in RAA is totally unexplored and could provide a powerful way to test the idea that we perceive music as a kind of emotional voice.

Redish et al. trace vulnerabilities in habit and planning systems almost exclusively to pharmacological effects of addictive substances on underlying brain systems. As we discuss, however, these systems also can be disrupted by purely psychological factors inherent in normal decision-making and everyday behavior. A truly unified model must integrate the contribution of both sets of factors in driving addiction.

A central theme of the unified framework for addiction advanced by Redish et al. is that there exists a common value or incentive process controlling Pavlovian and instrumental conditioning. Here we briefly review evidence from a variety of sources demonstrating that these incentive processes are in fact independent. Clearly the influence of Pavlovian predictors and goal values on choice offer distinct potential targets for pathologies of decision-making.

The fundamental assumption of compensation for visual delays states that, since delays are dealt with, there must be compensatory mechanisms. These mechanisms are taken to be internal models. Alternatives for delay compensation exist, suggesting that this assumption may not be fundamental, and nor should the existence of internal models be assumed. Delays may even be employed in their own compensation.

Current research on emotional responses to dissonance has yielded consistent data in both developmental psychology and neuroscience. What seems to be lacking is a definition of what might constitute dissonance in non-musical domains. Thus, contrary to Juslin & Västfjäll's (J&V) proposal for the need to distinguish between six broad mechanisms, I argue that future research should rather focus on perceptual determinants of each basic emotion.

We agree with many theoretical points presented by Rogers & McClelland (R&M), especially the role of domain-general learning of coherent covariation. Nonetheless, we argue that in failing to be informed by key aspects of development, including the role of labels on categorization and the emergence of constraints on learning, their model fails to capture important features of the ontogeny of knowledge.

People become addicted in different ways, and they respond differently to different interventions. There may nevertheless be a core neural pathology responsible for all distinctively addictive suboptimal behavioral habits. In particular, timing models of reward learning suggest a hypothesis according to which all addiction involves neuroadaptation that attenuates serotonergic inhibition of a mesolimbic dopamine system that has learned that cues for consumption of the addictive target are signals of a high-reward-rate environment.

In proposing that their model can operate in the concrete, perceptual world, Rogers & McClelland (R&M) have not done justice to the complexities of the ecological sphere and its invariance laws. The structure of concrete events forces a different framework, both for retrieval of events and concepts defined across events, than that upon which the proposed model, rooted in essence in the verbal learning tradition, implicitly rests.

Nijhawan argues convincingly that predictive mechanisms are pervasive in the central nervous system (CNS). However, scientific understanding of visual prediction requires one to formulate empirically testable neurophysiological models. The author's suggestions in this direction are to be evaluated on the basis of more realistic experimental methodologies and more plausible assumptions on the hierarchical character of the human visual cortex.

The emotional expression of laughter in opera scores and performance was evaluated by converting notation to temporal data and contrasting it with the conversational laughter it emulates. The potency of scored and sung laughter was assayed by its ability to trigger contagion in audiences.

Any theory of semantic cognition is also a theory of concepts. There are two ways to construe the models presented by Rogers & McClelland (R&M) in Semantic Cognition. If we construe the input and output representations as concepts, then the models capture knowledge acquisition within a stable set of concepts. If we construe the hidden-layer representations as concepts, the models provide a simulation of conceptual change.

Juslin & Västfjäll (J&V) think that all emotions aroused by music have the music itself as their “intentional object.” Some of the mechanisms they discuss almost certainly involve both cognitive appraisals and intentional objects. But some of the mechanisms are non-cognitive: they involve neither cognitive appraisals nor intentional objects. Partly for this reason they may produce moods rather than emotions proper.

Is the position of a moving target “predicted”? I argue that we should regard moving targets as the natural (veridical) position references. Motion is probably perceptually absolute, whereas position and time are relative quantities, as in physics. According to this view, processing delays are incorporated in the abstract local signs of motion signals. The flash-lag effect is one case in point.

Redish et al. propose a constellation of vulnerabilities inherent in the brain's decision-making system. They allow over-attention to cues a minor role in drug addiction. We think this is inadequate. Using the established links among drug cues, dopamine, and novelty, we propose a fuller account of this key feature of addiction, which we call the phenomenon of cue fascination.

Logically, weighting is transitive, but similarity is not, so clustering cannot be either. Entailments must help a child to review attribute lists more efficiently. Children's understanding of exceptions to generic claims precedes their ability to articulate explanations. So agency, as enabling constraint, may show coherent covariation with attributes, as mere extensional, observable effect of intensional entailments.

We wonder about tying the universal appeal of music to emotion as defined by psychologists. Music is more generally about feelings, and many of these, such as moods and pleasures, are central to the enjoyment of music and fall outside the domain of emotion. The critical component of musical feelings is affective intensity, resulting from syntactically generated implications and their outcomes.

Neuroscientists and psychologists have proposed a variety of well-supported theories to explain addiction. Many of these theories suggest that addiction results from a single process or dysfunction across all of its forms. The authors of the current review, in contrast, have used a well-defined theoretical account of decision-making to outline the variety of dysfunctions that could account for addictive behavior.