Nielsen's covert REM process model explains much of the mentation found in REM and NREM sleep, but stops short of postulating an interaction of waking cognitive processes with the dream mechanisms of REM sleep. It ranks with the Hobson et al. paper as a major theoretical advance. The Solms article does not surmount the ever-present problem of defining dreams in a manner conducive to advancing dream theory. Vertes & Eastman review the REM sleep and learning literature, but make questionable assumptions in doing so.

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

We have analyzed many discrimination learning difficulties as reflecting multiple stimulus control topographies (SCTs). Nevin & Grace's analysis offers new variables to consider in the design of stimulus-control shaping procedures and cross-setting generalization of newly established behavior. A multiple-SCT perspective also suggests that fixed-trial discrimination procedures may offer advantages for reconciling momentum theory and partial reinforcement extinction effects.

From the standpoint of decision research, investigating global heuristics like LEX is not fruitful, because we know already that people use partial heuristics instead. It is necessary (1) to identify partial heuristics in different tasks, and (2) to investigate rules governing their application and especially their combination. Furthermore, research is necessary into the adequate level of resolution of the elements in the toolbox.

Several suggestions are made for revision of Strategic Pluralism Theory (SPT). One revision requires recognition of the impact of individual differences in cognitive and behavioral competence on optimal mating strategy. In addition, SPT may need to incorporate certain self-regulatory processes such as the impact of widespread valuation of mates with one trait on their availability.

Shors & Matzel (1997) suggest replacing the question “Is LTP a mechanism of learning?” with “Is LTP a mechanism of arousal and attention?” However, the failure of experiments to verify the LTP-learning hypothesis may arise not because it is untrue, but because in its current guise, it is not properly testable. If so, then the LTP-attention hypothesis is untestable, as well.

The absence of a clear influence of the responses modified by new connections created by LTP on the development of these connections casts doubt on an essential role of LTP in learning and memory formation without any association with reinforcement. The evidence for the involvement of the monoaminergic systems in synaptic potentiation in the cerebral cortex during learning is adduced, and their role in reinforcement system function is discussed.

Gangestad & Simpson's theory accounts for the existence of male strategic variation admirably well, although it does not specify the precise nature of the adaptation linking male developmental stability to strategic pluralism. In contrast, female strategic variation remains elusive. Empirical data suggest that genetic variation partly underlies such variation, but the causes of female strategic differences largely remain unexplained.

Nielsen's concept of “covert REM sleep” accounts for more of the complexity in sleep psychophysiology than its conceptual predecessors such as the tonic-phasic model. With new neuroimaging findings, such concepts lead to more precise sleep psychophysiology including both traditional polysomnographic signs and neuronal activity in greater proximity to the actual point sources and distributed networks which generate dreaming.

[Hobson et al.; Nielsen]

Grace's contextual-choice model can account for the results from many studies on choice under concurrent-chain schedules. However, other models, including one that I call the “hyperbolic value-added model,” can also account for these results. Preference and resistance to change may indeed be related, but the best model of preference remains to be determined.

Gigerenzer, Todd, and the ABC Research Group give an interesting account of simple decision rules in a variety of contexts. I agree with their basic idea that animals use simple rules. In my commentary I concentrate on some aspects of their treatment of decision rules in behavioural ecology.

A mathematical approach to heuristics is proposed, in contrast to Gigerenzer et al.'s assertion that laws of logic and probability are of little importance. Examples are given of effective heuristics in abstract settings. Other short-comings of the text are discussed, including omissions in psychophysics and cognitive science. However, the authors' ecological view is endorsed.

Long-term potentiation (LTP) is a long-lasting increase in synaptic efficacy that many consider the best candidate currently available for a neural mechanism of memory formation and/or storage in the mammalian brain. In our target article, LTP: What's learning got to do with it?, we concluded that there was insufficient data to warrant such a conclusion. In their commentaries, Jeffery and Zhadin raise a number of important issues that we did not raise, both for and against the hypothesis. Although we agree with a number of these issues, we maintain that there remains insufficient evidence that LTP is a memory mechanism.

The concept of behavioural mass provides one avenue for justifying (or making rational) the phenomenon of declining impatience, according to which decision makers put more value on delays that will occur in the near future than on those that will occur later.

Gangestad & Simpson's arguments may be rendered more substantial and precise by capitalizing on research and theory on choice between reinforced response alternatives. An analysis in terms of feedback functions shows that the effects of individual differences in attractiveness may be understood as constraints on optimality and may be reconciled with the previous research and theory that the authors criticize.

There has been no generally accepted cognitive definition of dreaming. An electrophysiologic correlate (REM sleep) has become its defining characteristic. Dreaming and REM sleep are complex states for which the Dreaming + REMs model is over-simplified and limited. The target articles in this BBS special issue present strong evidence for a dissociation between dreaming and REM sleep.

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

As highlighted by Solms, and to a lesser extent by Hobson et al. and Nielsen, dreaming and REM sleep can be dissociated. Meanwhile Vertes & Eastman and Revonsuo provide distinct views on the functions of REM sleep and dreaming. A resolution of such divergent views may clarify the fundamental nature of these processes. As dream commentators have long noted, with Revonsuo taking the lead among the present authors, emotionality is a central and consistent aspect of REM dreams. A deeper consideration of emotions in REM dreams may serve as the conceptual salve to help heal the emerging rifts in this field of inquiry.

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

Replacing logical coherence by effectiveness as criteria of rationality, Gigerenzer et al. show that simple heuristics can outperform comprehensive procedures (e.g., regression analysis) that overload human limited information processing capacity. Although their work casts long overdue doubt on the normative status of the Rational Choice Paradigm, their methodology leaves open its relevance as to how decisions are actually made.

Chow's endorsement of a limited role for null hypothesis significance testing is a needed corrective of research malpractice, but his decision to place this procedure in a hypothetico-deductive framework of Popperian cast is unwise. Various failures of this version of the hypothetico-deductive method have negative implications for Chow's treatment of significance testing, meta-analysis, and theory evaluation.

Behavioral momentum is a useful metaphor reminding us that with constant conditions, ongoing behavior – in the form of response rate – would be expected to remain constant. But despite an impressive array of behavioral experiments, the concept has not yet been applied in a way that would make it useful as a general behavioral law.

Human mating strategies are contingent on individual prospects. Gangestad & Simpson provide a useful framework to explore these differing prospects, but do not take sufficient account of what is known ethnographically about mating decisions. Women often do not select their own long term mates. Men often have two or more long term mates, and can invest in the offspring of short term matings also.