Three issues are raised in this commentary. First, the mapping of semantic information into the different layers could be done in a more realistic way by using the Context layer to represent situational contexts. Second, a way to differentiate category membership information from other property information needs to be considered. Finally, the issue of modal knowledge is raised.

The “unified framework” for addiction proposed by Redish and colleagues is only unified at a reductionist level of analysis, the biological one relating to decision-making. Theories of addiction may be complementary rather than mutually exclusive, suggesting that limitations of individual theories might be unified through the combination of ideas from different biopsychosocial “complex” systems perspectives.

Although Redish et al. have pulled together a large number of approaches to understanding decision-making and common errors in cognition, they have outlined neither the necessary nor the sufficient attributes of addiction. They are correct in claiming that addiction is multifaceted and probably more akin to a syndrome than a genuine disease. But grasping what that multifaceted syndrome is still eludes us.

Neuroconstructivist modeling can be usefully extended with algorithms that build their own topology and recruit existing knowledge, effectively constructing a hierarchy of network modules. Possible benefits include allowing abilities to emerge naturally, in a way that affords objective study, deeper insights, and more rapid progress, and provides more serious consideration of the implications of constructivism.

Rogers & McClelland (R&M) criticize models that rely on structured representations such as categories, taxonomic hierarchies, and schemata, but we suggest that structured models can account for many of the phenomena that they describe. Structured approaches and parallel distributed processing (PDP) approaches operate at different levels of analysis, and may ultimately be compatible, but structured models seem more likely to offer immediate insight into many of the issues that R&M discuss.

Nijhawan redraws our attention to the problem of accurately perceiving an ever-changing visual world via a sensory system that has finite and significant communication times. The quandary is compelling and stark, but the suggestion that the visual system can compensate for these transmission delays by extrapolating the present is not so unequivocal. However, in this current airing of contradictory issues, accounts, and findings, Nijhawan trades spatial extrapolation – a rather specific concept introduced earlier (in Nijhawan 1994) for visual prediction – a far more expansive notion that forces the issue of both the perceived reality and functional significance of compensation.

Contemporary behavioral and brain scientists consider the existence of so-called basic emotions in a similar way to the one described by Erickson for so-called basic tastes. Commenting on this analogy, I argue that similar basic problems are encountered in both perspectives, and I suggest a potential nonbasic solution that is tested in emotion research (i.e., the appraisal model of emotion).

Juslin & Västfjäll (J&V) propose a theoretical framework of how music may evoke an emotional response. This commentary presents results from a pilot study that employed young children as participants, and measured musically induced emotions through facial expressions. Preliminary findings support certain aspects of the proposed theoretical framework. The implications of these findings on future research employing the proposed framework are discussed.

In this response, we consider four main issues arising from the commentaries to the target article. These include further details of the theory of interactive specialization, the relationship between neuroconstructivism and selectionism, the implications of neuroconstructivism for the notion of representation, and the role of genetics in theories of development. We conclude by stressing the importance of multidisciplinary approaches in the future study of cognitive development and by identifying the directions in which neuroconstructivism can expand in the Twenty-first Century.

Neural activity in the middle temporal area (MT) is strongly correlated with motion perception. I analyzed the temporal relationship between the representation of direction in MT and the actual direction of a stimulus that continuously changed direction. The representation in MT lagged the stimulus by 45 msec. Hence, as far as the perception of direction is concerned, the hypothesis of lag compensation can be rejected.

Gustatory studies are predicated on the existence of basic tastes. Erickson questions this assumption and offers contrary evidence. Although Erickson may conflate certain concepts and demand uncommonly stringent requirements for basic tastes, his thoughtful article reminds us that the basic organization of taste is not yet settled.

Key premises of the target article by Juslin & Västfjäll (J&V) are challenged. It is also shown that most of the six “psychological mechanisms” proposed by the authors as underlying the induction of emotion by music involve nonmusical proximal causes. As a replacement for “musical emotions,” the state of being-moved – from the recently developed Aesthetic Trinity Theory – is proposed.

The parallel distributed processing (PDP) perspective brings forward the important point that all semantic phenomena are based on analog underlying mechanisms, involving the weighted summation of multiple inputs by individual neurons. It falls short of indicating, however, how the essentially discrete nature of semantic processing may emerge at the cognitive level. Bridging this gap probably requires attractor networks.

We commend Redish et al. for the progress they have made in bringing a measure of theoretical order to the processes that underlie drug addiction. However, incorporating information about situations in which drug users do not exhibit faulty decision-making into the theory would greatly enhance its generality and practical value. This commentary draws attention to the relevant human substance abuse literature.

Redish et al. view addictions as errors arising from the weak access points of the system of decision-making. They do not analytically distinguish between addictions, on the one hand, and errors highlighted by behavioural decision theory, such as over-confidence, representativeness heuristics, conjunction fallacy, and so on, on the other. Redish et al.'s decision-making framework may not be comprehensive enough to capture addictions.

Erickson's conclusion that if basic tastes are not appropriate at one level, reference to labeled lines is inappropriate at any level, depends on matters of definition and scope. His population model mirrors Young's theory of color perception. However, there is evidence for distinct pathways to the cortex for two cone-opponent and one achromatic channel. Depending on the use made of key terms, sensory systems may display both across-fiber and labeled-line features.

When examining how emotions are evoked through music, the role of musical expectancy is often surprisingly under-credited. This mechanism, however, is most strongly tied to the actual structure of the music, and thus is important when considering how music elicits emotions. We briefly summarize Leonard Meyer's theoretical framework on musical expectancy and emotion and cite relevant research in the area.

This commentary challenges Rogers & McClelland (R&M) to use their model to account for delusional belief formation and maintenance. The gradual development of delusions and the nature of disconnectivity in Capgras delusions are used to illustrate the role of emotional salience in delusions. It is not clear how this kind of emotional saliency can be represented within the current architecture.

The extent to which visual processing can proceed in the visual hierarchy without awareness determines the magnitude of perceptual delay. Increasing data demonstrate that primary visual cortex (V1) is involved in consciousness, constraining the magnitude of visual delay. This makes it possible that visual delay is actually within the optimal lengths to allow sufficient computation; thus it might be unnecessary to compensate for visual delay.

The time delay problem – that perception lives slightly in the past as a result of neural conduction – has recently attracted a considerate amount of attention in the context of the flash-lag effect. The effect refers to a visual illusion wherein a brief flash of light and a continuously moving object that physically align in space and time are perceived to be displaced from one another – the flashed stimulus appears to lag behind the moving object (Krekelberg & Lappe 2001). In the target article, Nijhawan compellingly argues that delay compensation could be undertaken by a predictive process in the feedforward pathways in the vision system. Before jumping into the quest for the mechanism of delay compensation, however, I would like to argue that the magnitude of delay has been overestimated, and that it might even be unnecessary to compensate for such a delay.

Saccades divide visual input into rapid, discontinuous periods of stimulation on the retina. The response of single neurons to such sequential stimuli is neuronal adaptation; a robust first response followed by an interval-dependent diminished second response. Adaptation is pervasive in both early and late stages of visual processing. Given its inherent coding of brief time intervals, neuronal adaptation may play a fundamental role in compensating for visual delays.