The advent of functional imaging has reinforced the attempts to define dreaming as a sleep state-dependent phenomenon. PET scans revealed major differences between nonREM sleep and REM sleep. However, because dreaming occurs throughout sleep, the common features of the two sleep states, rather than the differences, could help define the prerequisite for the occurrence of dreams.

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

The target article's finding of stable and general individual differences in solving of problems in heuristics-and-biases experiments is fundamentally subversive to the Meliorist research program's attention-getting claim that human thought is “systematically irrational.” Since some people get these problems right, studies of heuristics and biases may reduce to repeated demonstrations that difficult questions are hard to solve.

Grodzinsky's characterization of the syntactic function of Broca's area is convincing, but his argument that this transformation processing capability is specific to language is less so. Based on predictions from simulation studies of sequence learning, we report a correlation between agrammatic patients' impairments in (a) syntactic comprehension, and (b) nonlinguistic sequence transformation processing, indicating the existence of a nonlinguistic correlate of agrammatic aphasia.

Two categorization arguments pose particular problems for localist connectionist models. The internal representations of localist networks do not reflect the variability within categories in the environment, whereas networks with distributed internal representations do reflect this essential feature of categories. We provide a real biological example of perceptual categorization in the monkey that seems to require population coding (i.e., distributed internal representations).

Norris, McQueen & Cutler demonstrated that feedback is never necessary during lexical access and proposed a new autonomous model, that is, the Merge model, taking into account the known behavioral data on word recognition. For sentence processing, recent event-related brain potentials (ERPs) data suggest that interactions can occur but only after an initial autonomous stage of processing. Thus at this level too, there is no evidence in favor of feedback.

Rolls emphasizes the role of emotion in behavior. My commentary provides some balance to that position by arguing that stored social knowledge dominates our behavior and controls emotional states, thereby reducing emotions to a subservient role in behavior.

Recent investigations indicate that, around 7-months-of-age, infants begin to show some ability to recognize words in fluent speech. In segmenting and recognizing words, infants rely on information available in the speech signal. We consider what implications these findings have for adult word recognition models in general, and for Merge, in particular.

We focus on two components of Page's argument in favour of localist representations in connectionist networks: First, we take issue with the claim that localist representations can give rise to generalisation and show that whenever generalisation occurs, distributed representations are involved. Second, we counter the alleged shortcomings of distributed representations and show that their properties are preferable to those of localist approaches.

There are obvious flaws in REM sleep suppression paradigms that do not allow any conclusion to be drawn either pro or contra the REM sleep-memory hypothesis. However, less intrusive investigations of REM sleep suggest that this sleep stage or its adjunct neuroendocrine characteristics exert a facilitating influence on certain aspects of ongoing memory formation during sleep.

[Nielsen; Vertes & Eastman]

Many authors assume that Broca's area subserves the functions that are lost in patients with Broca's aphasia. This commentary attempts to clarify the relationship between Broca's area and Broca's aphasia and suggests that statements about the neurology of patients' specific language functions might be better supported by their individual structural neuroimaging data.

Rolls discusses various adaptive explanations of physiological processes and the emotions. We give a critical analysis of some of these from the perspective of behavioural ecology. While agreeing with the approach adopted by Rolls, we identify topics that could have been better presented by making use of the existing literature.

I discuss an aspect of individual differences which has not been considered adequately in the target article, despite its potential role in the rationality debate. Besides having different intellectual abilities, different individuals may produce different erroneous responses to the same problem. In deductive reasoning, different response patterns contradict deterministic views of deductive inferences. In decision-making, variations in nonoptimal choice may explain successful collective actions.

Stanovich & West continue a history of norm-setting that began with deference to reasonable people's opinions, followed by adherence to probability theorems. They return to deference to reasonable people, with aptitude test performance substituting for reasonableness. This allows them to select independently among competing theories, but defines reasoning circularly in terms of aptitude, while aptitude is measured using reasoning.

Rolls presents a good integrative summary of the neural bases of emotions, adds new findings and insights, and takes a stance on controversial issues such as separate or distinct brain systems for processing emotion information and for planning and action. This commentary raises questions about his explanations of emotion activation, response to novelty, the evolution of emotions, and the phenomenal experience of emotions in human consciousness.

The massive acoustic redundancy of minimally contrasting speech sounds, coupled with the auditory integration of psychoacoustically similar acoustic properties produces a highly invariant percept, which cannot be improved by top-down feedback from the lexicon. Contextual effects are also bottom-up but not all entirely auditory and may thus differ in whether they affect sensitivity or only response bias.

Nielsen's model presents a new isomorphic brain-mind viewpoint, according to which the sole dream generator is found in a REM-on (explicit or covert REM) mechanism. Such a model cannot explain the dreamlike activity during SWS (slow wave sleep), SO (sleep onset) and in the last period of sleep. Moreover the hypothesis contrasts with Solms's data, which show that dreaming is present also in case of destruction of the REM generator.

[Nielsen; Solms]

Grodzinsky examines Broca's aphasia in terms of some specific grammatical deficits. However, his grammatical models offer no way to characterize the distinctions he observes. Rather than grammatical deficits, his patients seem to have intact grammars but defective modules of parsing and production.

The notion of a “familiar example” used in Page's definition of a “localist model” is shown to be meaningful only with respect to the types of tasks faced by the connectionist model. It is also shown that the modeling task ultimately dictates which choice of model: “localist” or “distributed” is most appropriate.

Rolls presents a theory of emotion based on the premise that emotions are evoked by events that are capable of being instrumental reinforcers and punishers. As support for this theory is drawn almost entirely from experiments in non-human primates, valuable insights into the relationship between punishment and reinforcement systems, and the nature of instrumentality, may have been overlooked.

We criticize the lack of neuroanatomical precision in the Grodzinsky target article. We propose a more precise neuroanatomical characterization of syntactic processing and suggest that syntactic procedures are supported by the left frontal operculum in addition to the anterior part of the superior temporal gyrus, which appears to be associated with syntactic knowledge representation.