Behrendt & Young's (B&Y's) novel “unifying model” of hallucinations, although comprehensive, fails to incorporate research into the possible role of 5-HT2A receptors in the mode of action of novel “atypical” antipsychotic drugs (which treat hallucinations effectively), and into the role of such receptors, which are located in thalamocortical circuits, in mediating drug-induced hallucinations.

A self-experiment by Roberts found that watching faces on early morning television triggered a delayed rhythm in mood. This surprising result is compared with previous research on circadian rhythms in mood. I argue that Roberts' dual oscillator model and theory of Stone-Age living may not provide the explanation. I also discuss the implications of self-experiments for scientific practices.

The commentators' responses to The Illusion of Conscious Will reveal a healthy range of opinions – pro, con, and occasionally stray. Common concerns and issues are summarized here in terms of 11 “frequently asked questions,” which often center on the theme of how the experience of conscious will supports the creation of the self as author of action.

The emulation theory of representation is developed and explored as a framework that can revealingly synthesize a wide variety of representational functions of the brain. The framework is based on constructs from control theory (forward models) and signal processing (Kalman filters). The idea is that in addition to simply engaging with the body and environment, the brain constructs neural circuits that act as models of the body and environment. During overt sensorimotor engagement, these models are driven by efference copies in parallel with the body and environment, in order to provide expectations of the sensory feedback, and to enhance and process sensory information. These models can also be run off-line in order to produce imagery, estimate outcomes of different actions, and evaluate and develop motor plans. The framework is initially developed within the context of motor control, where it has been shown that inner models running in parallel with the body can reduce the effects of feedback delay problems. The same mechanisms can account for motor imagery as the off-line driving of the emulator via efference copies. The framework is extended to account for visual imagery as the off-line driving of an emulator of the motor-visual loop. I also show how such systems can provide for amodal spatial imagery. Perception, including visual perception, results from such models being used to form expectations of, and to interpret, sensory input. I close by briefly outlining other cognitive functions that might also be synthesized within this framework, including reasoning, theory of mind phenomena, and language.

According to Roberts, self-experimentation is a viable tool for idea generation in the behavioral sciences. Here we discuss some limitations of this assertion, as well as particular design and data-analytic shortcomings of his experiments.

Falk claims that human language took a step forward when infants lost their ability to cling and were placed on the ground, increasing their fears, which mothers assuaged prosodically. This claim, which is unsupported by anthropological and psychological evidence, would have done little for the syllabic and segmental structure of language, and ignores infants' own contribution to the process.

Behrendt & Young (B&Y) suggest that hallucinations occur as a result of decoupling of neuronal populations from sensory control. I propose that such a decoupling is in fact a constant feature of brain activity, even under nonpathological conditions. This position is justified by evidence from recent neurophysiological recording studies. I suggest that hallucinations arise because of a breakdown in segregation of internally and externally generated activity in a neuronal population.

Carpendale & Lewis's (C&L's) proposal of a social interaction account makes clear the need for researchers of all theoretical orientations to get specific about how social experience influences children's developing understanding of mind, but it is premature to reject other theories, such as theory-theory, which also attribute a major role to experience.

The proposal to add the behavioral momentum metaphor to Skinnerian psychology and the use of other borrowed physical explanatory concepts such as velocity and inertial mass has only superficial value. The basic problem is that, in contrast to Newtonian physics, the “laws” do not apply to a significant proportion of the phenomena to be explained, and these evidential discrepancies are ignored, rather than being used to modify the scientific explanations and improve technological applications that are based on those explanations.

Transcranial magnetic stimulation, EEG, and behavioral studies by our group implicate spurious activation of speech perception neurocircuitry in the genesis of auditory hallucinations in schizophrenia. The neurobiological basis of these abnormalities remains uncertain, however. We review our ongoing studies, which suggest that altered cortical coupling underlies speech processing in schizophrenia and is expressed via disrupted gamma resonances and impaired corollary discharge function of self-generated verbal thought.

Self-experimentation is uncommon in the decision sciences, but mental experiments are common; for example, intuition and introspection are often used by theoretical economists as justifications for their models. While introspection can be useful for the generation of ideas, it can also be overused and become a comfortable illusion for the theorist and an obstacle for science.

In this commentary we raise three issues: (1) Is it motherese or song that sets the stage for very early mother-infant interaction? (2) Does the infant play a pivotal role in the complex temporal structure of social interaction? (3) Is the vocal channel primordial or do other modalities play an equally important role in social interaction?

Grush has proposed a fairly comprehensive version of the idea of internal models within the framework of the emulation theory of representation. However, the formulation suffers from assumptions that render such models biologically infeasible. Here I present some problems from physiological principles of human movement production to illustrate why. Some alternative views to emulation are presented.

A central pillar of Carpendale & Lewis's (C&L's) argument is Wittgenstein's later work on language. I suggest that this support is not as strong as might be wished, and offer an alternative approach to their conclusion that language learning, especially of folk psychology, involves a socially embedded constructivism.

Behrendt & Young (B&Y) propose a useful theoretical framework for the study of processes underlying perception and hallucinations. It focuses on gamma oscillations in thalamocortical networks and the role of the reticular thalamic nucleus in modulating these oscillations. I suggest that their theoretical model might also be applied to the investigation of temporal encoding deficits in disorders such as dyslexia. I further suggest, however, that a role for slower rhythms, such as theta, might also be considered when investigating perceptual experience.

The topics discussed in this response are in four broad areas: (1) Idea generation, including the failure to discuss and teach idea generation and how to nurture new ideas (sect. R2), sources of ideas worth testing with self-experimentation (sect. R3), and unusual features of the situation that may have increased the discovery rate (sect. R4); (2) Miscellaneous methodological issues, such as the value of mental experiments (sect. R5) and the limitations of double-blind experiments (sect. R6); (3) Subject-matter issues, including the relationship of this work to other evolutionary psychology studies and a new way to test evolutionary explanations (sect. R7), as well as questions about the mood results (sect. R8) and the weight results (sect. R9); and (4) Self-experimentation, including its difficulty (sect. R10) and future (sect. R11).

Behavioral momentum theory has evolved within the realm of operant conditioning. The thought-provoking momentum metaphor equates the strength of an operant response with its resistance to change and preference (i.e., choice) for that response over other available responses. Whereas baseline response rate (velocity in the metaphor) is assumed to be largely influenced by the response-reinforcer contingency, resistance to change and preference are assumed to reflect an intervening variable called behavioral mass, which is determined primarily by the stimulus-reinforcer relationship. This invites the question of how well the momentum metaphor applies to the stimulus-reinforcer relationships of traditional Pavlovian paradigms. Presumably, a correspondence exists between behavioral mass and the notion of associative strength in the associative learning literature. Although response rate has little meaning in the trialwise structure of classical (i.e., Pavlovian) conditioning, response probability or magnitude might be regarded metaphorically as velocity. Momentum theory suggests that resistance to change (e.g., extinction) is a better indicator of associative strength than is response probability or magnitude. Therefore, variables that strengthen Pavlovian learning should influence resistance to extinction of conditioned responding in a similar manner. Moreover, it is important to assess momentum theory outside of strictly operant paradigms, particularly because in clinical settings many common disorders (e.g., phobias) and their therapies (e.g., cue exposure) are thought to be classically conditioned.

Carpendale & Lewis (C&L) emphasize the importance of viewing language as activity. In this commentary I push further their claim by highlighting how constructions, rather than words, are the appropriate unit of analysis. In addition, I suggest how a discussion of indexicality paves the way for a better understanding of how language provides a powerful tool for children's construction of mind.

I argue that a dynamical framing of the emulation theory of representation may be at odds with its articulation in Grush's information-processing terms. An architectural constraint implicit in the emulation theory may have consequences not envisaged in the target article. In my view, “how the emulator manages to implement the forward mapping” is pivotal with regard to whether we have an emulation theory of representation, as opposed to an emulation theory of (mere) applied forces.

Words denoting “mother” in baby talk and in languages usually include nasal sounds, supporting Falk's suggestion that infant nasalized demand vocalizations might have motivated a first word. The linguistic contrast between maternal terms and paternal terms, which favor oral consonants, and the simple phonetic patterns of parental terms in both baby talk and languages also suggest parental terms could have been first words.