Twenty-six commentators from several disciplines have written on the assumption that choice is determined by comparative valuation in a common denominator of reward, the “competitive marketplace.” There was no apparent disagreement that prospective rewards are discounted hyperbolically, although some found that the resulting predictions could come just as well from other models, including the interpretation of delay as risk and analysis in terms of hot versus cold valuation systems. Several novel ideas emerged.

Scientists should, above all else, value the truth. To do this effectively, scientists should separate their identities from the data they produce. It will be easier to make replications mainstream if scientists are rewarded based on their stance toward the truth – such as when a scientist reacts positively to a failure to replicate – as opposed to a particular finding.

We argue that an approach that treats short-term memory as activated long-term memory is not inherently in conflict with information recycling in a limited-capacity or working-memory store, or with long-term storage based on the processing in such a store. Language differences aside, real model differences can only be assessed when the contrasting models are formulated precisely.

Mormyrid teleosts have Purkinje cells with palisade dendrites, which probably represent coincidence detectors of parallel fiber activity. Their existence strongly supports the ideas of Braitenberg et al. on cerebellar function. However, the organization of mormyrid granule cells and parallel fibers suggests that a key to cerebellar function is not in interactions within one wave, but between two opposite tidal waves.

Phillips and colleagues claim that the representation of knowledge is more basic than the representation of belief, presupposing them to be categorically distinct mental states with distinct evolutionary purposes. We argue that the relationship between the two is much more complex, is further shaped by culture and language, and leaves its mark on manifestations of theory of mind and teaching.

Both Solms and Nielsen acknowledge the difficulty of accounting for the similarities between REM and NREM sleep mentation with a two-generator model, and each link dreams, either explicitly (Solms) or implicitly (Nielsen), to brain activation. At present, however, no data indicate that brain activation can be demonstrated whenever vivid dream reports are obtained.

[Nielsen; Solms]

Naive physics beliefs can be systematically mistaken. They provide a useful test-bed because they are common, and also because their existence must rely on some adaptive advantage, within a given context. In the second part of the commentary we also ask questions about when a whole family of misbeliefs should be considered together as a single phenomenon.

A “multifactorial” model should accommodate a psychological perspective, aiming to relate the phenomenology of complex visual hallucinations not only to neurobiological findings but also an understanding of the patient's psychological problems and situation in life. Greater attention needs to be paid to the role of the “lack of insight” patients may have into their hallucinations and its relationship to cognitive impairment.

Both of the companion target articles place considerable performance on music performance ability, with specific attention paid to singing in harmony for the music and social bonding (MSB) hypothesis proposed by Savage and colleagues. In this commentary, I evaluate results from recent research on singing accuracy in light of their implications for the MSB hypothesis.

Caplan & Waters's model differentiating levels of processing and the role of working memory is important and likely right. However, their claim rests on a lack of correlation between working memory and structural complexity. We examine sources of variability in these measures that remain unaccounted for (by anyone), variability that muddies a straightforward claim that the lack of correlation is cleanly established.

Merker's core idea, that the experience of being conscious reflects the interactions of actions, targets, and motivations in the upper brainstem, with cortex providing the content of the conscious experience, merits serious consideration. However, we have two areas of concern: first, that his definition of consciousness is so broad that it is difficult to find any organisms with a brain that could be non-conscious; second, that the focus on one cortical–subcortical system neglects other systems (e.g., basal forebrain and brainstem cholinergic systems and their cortical and thalamic target areas) which may be of at least equal significance.