Page's proposal to stipulate representations in which individual units correspond to meaningful entities is too unconstrained to support effective theorizing. An approach combining general computational principles with domain-specific assumptions, in which learning is used to discover representations that are effective in solving tasks, provides more insight into why cognitive and neural systems are organized the way they are.

The proposition that feedback is never necessary in speech recognition is examined for utterances consisting of sequences of words. In running speech the features near word boundaries are often modified according to language-dependent rules. Application of these rules during word recognition requires top-down processing. Because isolated words are not usually modified by rules, their recognition could be achieved by bottom-up processing only.

The standard dogmatism ignores the fact that neural coding is extremely flexible, and the degree of “coarseness” versus “locality” of representation in real brains can be different under different task conditions. The real question that should be asked is: What is the operating point of neural coding under natural behavioural conditions? Several sources of evidence suggest that under natural conditions some degree of distribution of coding pervades the nervous system.

Norris et al.'s claim that feedback is unnecessary is compromised by (1) a questionable application of Occam's razor, given strong evidence for feedback in perception; (2) an idealization of the speech recognition problem that simplifies those aspects of the input that create conditions where feedback is useful; (3) Norris et al.'s use of decision nodes that incorporate feedback to model some important empirical results; and (4) problematic linking hypotheses between crucial simulations and behavioral data.

This commentary argues for the inclusion of the neurophysiological arousal concept to help understanding the brain mechanisms of emotions and reward and the cognitive mechanisms involved.

Grodzinsky's general approach to the neuroscience of language is interesting, but the evidence currently available has problems with pragmatic infelicity in experiments involving Japanese scrambling and the interpretation of experimental results on Japanese indirect passives. I will suggest a more direct way of testing the Trace-Deletion Hypothesis (TDH).

Tasks in the adult reasoning literature are designed so that heuristic processing leads one astray and adequate rule-based processing requires explicit knowledge about applicable logical and quasi-logical norms. Other research, however, indicates that appropriate rule-based inferences can be automatic. Individual differences in rationality are largely due to differences in developmental progress toward metacognitive understanding of both heuristic and rule-based inferences.

The evolutionary theory of threat simulation during dreaming indicates that themes appropriate to ancestral survival concerns (threats) should be disproportionately represented in dreams. Our studies of typical dream themes in students and sleep-disordered patients indicate that threatening dreams involving chase and pursuit are indeed among the three most prevalent themes, thus supporting Revonsuo's theory. However, many of the most prevalent themes are of positive, not negative, events (e.g., sex, flying) and of current, not ancestral, threat scenarios (e.g., schoolwork). Moreover, many clearly ancestral themes (e.g., snakes, earthquakes) are not prevalent at all in dreams. Thus, these findings challenge the specificity of the threat simulation theory.

[Revonsuo]

Despite its explanatory value, the “higher order linguistic thought” model comes up short as an account of the felt aspect of motivational states.

Reflective waking mentation is supported by cortical activating and inhibitory processes. The thought-like mental content of slow wave sleep appears with lower levels of both kinds of influence. During REM sleep, the equation: activation + disinhibition + dopamine may explain the often psychotic-like mode of psychological functioning.

[Hobson et al.; Nielsen; Revonsuo; Solms; Vertes & Eastman]

Grodzinsky proposes that agrammatism leads to a “pruning” of the syntactic tree in speech production. For German, this assumption predicts that syntactic processes related to functional projections AgrP and CP should be impaired. An analysis of spontaneous-speech data from four Broca's aphasics with respect to subject-verb agreement and verb placement, however, indicates that phrase-structure representations in agrammatism are intact.

Norris, McQueen & Cutler present a detailed account of the decision stage of the phoneme monitoring task. However, we question whether this contributes to our understanding of the speech recognition process itself, and we fail to see why phonotactic knowledge is playing a role in phoneme recognition.

Stanovich & West's claim that there are two coherent and conceptually distinct types of thinking, System 1 and System 2, is questioned. Some authors equate System 2 with intelligence whereas other do not; and some authors regard the two types of system as distinct while others regard them as lying on a continuum.

Page has performed an important service by dispelling several myths and misconceptions concerning the localist approach. The localist position and computational model presented in the target article, however, are overly restrictive and do not address the representation of complex conceptual items such as events, situations, actions, and plans. Working toward the representation of such items leads to a more sophisticated and articulated view of the localist approach.

Paradoxical individual differences, where a dysfunctional trait correlates positively with some preconceived notion of the normatively correct answer, provide compelling evidence that the wrong norm has been adopted. We have found that logical performance on conditional inference is positively correlated with schizotypy. Following Stanovich & West's reasoning, we conclude that logic is not normative in conditional inference, the prototypically logical task.

Grodzinsky claims that “normal language users demonstrate trace-antecedent relations in real-time tasks.” However, the cited evidence is equally compatible with a traceless account of processing. Moreover, Pickering and Barry (1991) and Traxler and Pickering (1996) have demonstrated that the processor does not wait until the purported trace location before forming the dependency. Grodzinsky's claims about Broca's area should be interpreted in terms of a transformation-free account.

The Page target article is interesting because of apparent coverage of many psychological phenomena with simple, unified neural techniques. However, prototype phenomena cannot be covered because the strongest response would be to the first-learned stimulus in each category rather than to a prototype stimulus or most frequently presented stimuli. Alternative methods using distributed coding can also achieve portability of network knowledge.

Rolls's mechanistic account of emotion can help to bridge a rift within the field of evolutionary psychology. One side of the rift emphasizes the importance of innate psychological mechanisms that evolved to solve specific problems encountered in the ancestral environment. The other side emphasizes learning, development, and culture as open-ended evolutionary processes in their own right. Rolls shows how these two views can be reconciled, allowing a productive middle ground to be explored.

I agree with Norris et al. that feedback to a phonemic level is never necessary, but disagree strongly with their reason why this is true. I believe the available evidence indicates that there is no feedback because there is no phonemic level employed in the perceptual processing of speech.

In this commentary I discuss the importance of considering the isomorphism between the full richness of dreams and the great body of information about REM sleep that is amply documented in the five target articles. With this inclusive mode I point out the importance of looking at REM sleep as involving both pontine and cortical activity in an integrated network. We cannot have a full appreciation of sleep and dreaming (view of the forest) without taking both physiology and mental activity seriously.

[Hobson et al., Nielsen, Revonsuo, Solms, Vertes & Eastman]