Metaphors have three important functions in scientific discourse: heuristic, rhetorical, and epistemic. I argue that, contrary to prevailing opinion, metaphors are indispensable components of scientific methodology as well as scientific communication. Insofar as the choice of metaphors reflects ideological commitments, all science is ideological. The philosophically vexed question is how to characterize the sense in which science is not merely ideological.

O'Brien & Opie defend a “vehicle” rather than a “process” theory of consciousness largely on the grounds that only conscious information is “explicit.” I argue that preconscious and unconscious representations can be functionally explicit (semantically well-formed and causally active). I also suggest that their analysis of how neural activation space mirrors the information structure of phenomenal experience fits more naturally into a dual-aspect theory of information than into their reductive physicalism.

As well as data indicating relationships (emphasised in the target article) (1) between dopaminergic transmission in the nucleus accumbens and positive incentive motivation, and (2) between dopaminergic transmission and extraversion, other data (not accounted for by the hypotheses developed in the target article) indicate relationships (3) between accumbens dopaminergic transmission and cognitive, especially perceptual, processes that are disrupted in schizophrenia, and (4) between dopaminergic transmission and psychoticism. The tension between relationships 1 + 2 and 3 + 4 is discussed and a tentative resolution proposed.

This commentary takes issue with two of Rose's central themes from the perspective of the psychology of intelligence. In the case of reductionism, I argue that Rose fails to live up to his own rhetoric by claiming a veto from his own discipline (biology) over facts of the matter in another (psychology). In the case of “Lifelines,” Rose's argument is contradicted by evidence from both individual differences and developmental change in intelligence.

Evidence reveals numerous cross-cultural universals regarding human mental processes and behavior. Similarly, cross-cultural data are consistent with predictions from theories of kin selection, reciprocal altruism, and sexual selection inspired by Darwin's theory of evolution by natural selection. Thus, the “annals of human behaviour” do provide “example[s] fitting the sociobiological bill,” (Lifelines, p. 202) thereby, supporting sociobiological accounts of human behavior.

Depue & Collins's model of incentive-motivational modulation of goal-directed behavior subserved by a medial orbital prefrontal cortical (MOC) network is appealing, but it leaves several questions unanswered: How are the stimuli that elicit an incentive motivational state selected? How does the incentive motivational state created by the MOC network modulate behavior? What is the function of the dopaminergic input to the striatum? This commentary suggests possible answers, based on the open-interconnected model of basal-ganglia-thalamocortical circuits, in which the limbic circuit selects goals and, via its connections with the motor and the associative circuits, directs behavior according to those goals, elaborating on the role of dopamine.

Though we fully agree that unconscious processing produces explicit representations that form the conscious phenomenal experience of the subject, identifying phenomenal experience with stable patterns of activation in a PDP network seriously limits O'Brien & Opie's thesis. They fail to recognize the constructive role of consciousness during the learning episode itself, reducing consciousness to a resulting outcome of the learning episode. We illustrate how consciousness can guide and shape the formation of increasingly structured representations of the world by presenting a brief outline of a model for speech segmentation.

Steven Rose regards oversimplification of biology as the supreme sin, inevitably leading to evil consequences, and requiring an unique distortion of scientific practice to avoid it. To avoid this, he proposes a short-cut to scientific knowledge by defining certain areas of biology that are intrinsically flawed. But this achieves only a subordination of science to politics. There are no general-purpose shortcuts for evaluating the validity of theories, and no substitutes for testing specific theories using relevant evidence.

Interpreting VTA dopamine activity as a facilitator of affective engagement fits Depue & Collins's agency dimension of extraverted personality and also Watson's and Tellegen's (1985) engagement dimension of state mood. Serotonin, by turning down the gain on dopaminergic affective engagement, would permit already prepotent responses or habits to prevail against the behavior-switching incentive-simulation-driven temptations of the moment facilitated by fickle VTA DA. Intelligent switching between openly responsive affective engagement and constraint by long-term plans, goals, or values presumably involves environment-sensitive balancing of these neuromodulators, such as socially dominant primates may show.

O'Brien & Opie make unnecessary distinctions between vehicle and process theories and neglect empirically based distinctions between conscious and unconscious processing. We argue that phenomenal experience emerges, not just as a byproduct of input-driven parallel distributed processing, but as a result of constructive processing in recurrent neural networks. Stable network states may be necessary, but are not sufficient, for consciousness.

O'Brien & Opie argue that (1) only explicit representations give rise to conscious experience, and (2) explicit representations depend on stable patterns of activation. In neglect patients, the stimuli presented to the neglected hemifield are not consciously experienced but exert causal effects on the processing of other stimuli presented to the intact hemifield. We argue that O'Brien & Opie cannot account for a nonconscious representation that is stable, as attested by the fact that it affects behavior, but is neither potentially explicit nor tacit.

Metabolic systems are complicated and contain very large numbers of interacting reactions and many internal regulatory mechanisms. This does not prevent the genetic composition of an organism from influencing its behavior, however, nor does it preclude the possibility that some aspects of its behavior may be amenable to simple explanations.

The Depue & Collins model is intended to explain a normal human personality trait: extraversion. In contrast, attention-deficit/hyperactivity disorder (ADHD) is generally considered to be a type of psychopathology not found in so-called normals; however, the clinical and neurobiological research done on ADHD seems to amplify and support Depue & Collins's model.

Rose's Lifelines justifiably attacks the rigid genetic determinism that pervades the popular press and even some scientific writing. Genes do not equate with destiny. However, Rose's argument should not be taken too far: genes do influence behavior, in animals as well as in man.

The connectionist vehicle theory of phenomenal experience in the target article identifies consciousness with the brain's explicit representation of information in the form of stable patterns of neural activity. Commentators raise concerns about both the conceptual and empirical adequacy of this proposal. In the former regard, they worry about our reliance on vehicles, representation, stable patterns of activity, and identity. In the latter regard, their concerns range from the general plausibility of a vehicle theory to our specific attempts to deal with the dissociation studies. We address these concerns, and then finish by considering whether the vehicle theory we have defended has a coherent story to tell about the active, unified subject to whom conscious experiences belong.

Depue & Collins [D&C] propose a well-conceived and nicely detailed theory of the involvement of dopaminergic connections in extraversion. Since these systems are hypothesized to be associated with reward sensitivity, other neural systems that are involved with reward sensitivity should be considered as well. In this commentary it is argued that there is now enough evidence for the involvement of the left and right frontal regions of the brain in approach and withdrawal behavior that it should also be considered in theories of personality such as D&C's. Integration of predominantly subcortical and cortical theories of personality/brain function may produce a more comprehensive picture of temperament and personality.

Depue & Collins's (D&C's) work relies on extrapolation from data obtained through studies in experimental animals, and needs support from studies of the role of dopamine (DA) neurotransmission in human behaviour. Here we review evidence from two sources: (1) studies of patients with Parkinson's disease and (2) positron emission tomography (PET) studies of DA neurotransmission, which we believe lend support to Depue & Collins's theory, and which can potentially form the basis for a true neurochemistry of personality.

If the explanatory gap between phenomenal consciousness (“p-consciousness”) and the brain cannot be closed by current naturalistic theories of mind, one might instead try to dissolve the explanatory gap problem. We hold that such a dissolution can start from the notion of consciousness as a social construction. In his target article, however, Block (1995) argues that the thesis that consciousness is a social construction is trivially false if it is construed to be about phenomenal consciousness. He ridicules the idea that the occurrence of p-consciousness requires that the subject of p-consciousness already have the concept of p-consciousness. This idea is not as ridiculous as Block supposes. To see this, one must accept that in a unique sense, p-consciousness is what we as the subjects of consciousness take it to be. Furthermore, the notion of consciousness as a social construction does not depend on the view that the concept of consciousness somehow precedes the occurrence of consciousness as such. In sum, consciousness can plausibly be seen as a social construction, and this view can promote a dissolution of the explanatory gap problem.

Lifelines supports the theme that behavioral development is a fluid, life-long phenomenon. In contrast, many emotional and cognitive traits are subject to strong genetic influence, and are highly stable over many years. The manner in which neuroplasticity and trait stability cooccur needs to be modeled. An outline of such a model is provided to promote discussion of this complex issue.

Professor Rose is inflamed against the views of Richard Dawkins concerning genetic determinism. He has constructed an image of a much stupider and eviller Dawkins view than is likely to be true and argues against it. This is unrewarding, but otherwise his discussion of biology is very interesting.