Upon consideration of the unconditioned and particularly the conditioned stimuli that have been proposed to participate in the generation of incentive motivational states and, by extension, of extraversion, the nature of the contribution of NAS DA becomes less clear. Different kinds of conditioned stimuli can also exert strong control over the expression of behavioral sensitization. How might such stimuli affect the ability of experience-dependent processes to introduce stable individual differences in the development and expression of extraversion trait levels?

Rose presents an important critique of the determinism and reductionism of modern biology. However, such trends are probably temporary aberrations in the development of science. Another form of determinism which has deeper roots is emerging from modern studies of brain dynamics. To reconcile this evidence with the concept of a “person” will require more radical rethinking of our received notion of natural law.

Steven Rose's book is essentially a plea for considering the variety and complexity of life and against simplistic reductions of human and animal behavioral phenomena to single genetic causes.

Is a generalized positive incentive motivation a construct appropriate to the human level of behavior or would sensation or novelty seeking be a more appropriate one? Is positive incentive motivation, or susceptibility to signals of reward, a mechanism related only to extraversion traits including sociability, activation, social potency, and positive affect? Research shows that susceptibility to reward is related to impulsive sensation seeking and aggression as well as sociability and an aroused type of positive affect. Comparative and indirect human correlates suggest an involvement of dopaminergic reactivity in sensation seeking and sociability.

The commentaries on our target article address three main areas: (1) the relative importance of extraversion and other related traits to DA functioning, (2) how the long-term stability of extraversion can be conceptualized within a highly plastic central nervous system, and (3) the nature of DA functioning in the MOC network and in extraversion. We have organized our Response, therefore, into three major sections.

Extending lifelines still further, beyond determinism leads to doubt about females' ability to select mates with “good genes,” and to a scenario for troop selection and to a link with questions of scale in ecology.

This commentary on Müller's target article is designed to help bridge the gap between method and theory in neurobiological approaches to language. We focus on pathonormal inference as reflective of broader conceptual issues concerning universality and modularity. Our commentary directs attention to how current methodological and analytic procedures are less than optimal and minimize possibilities for reaching theoretical consensus. We make suggestions about alternative analytic strategies that provide a direction for future scientific progress.

While agreeing with Rose's reasoning about why the causes of organisms' behaviors cannot be reduced to the solely biological and molecular, this review questions Rose's uses of the terms “determinism” and “contingency”; his occasional seemingly cavalier acceptance as fact of unproven hypotheses about social and psychological phenomena; and his general disdain for the psychometric tradition and its causal modeling extensions.

The derivation of heritability from human twin studies involves serious methodological flaws. Heritability is consistently overestimated because of biological confounds of twinning, consistent and often gross underestimation of the environmental variance, and nonadditive genetic influences that can hugely exaggerate heritability values. Despite this bad research design, behaviour geneticists continue to publish results implying that their heritability results are valid.

The natural communication system of chimpanzees has some unique characteristics rooted in two possible ways of producing call variants in primates. The chimpanzee call repertoire contains variants available to all group members. The transfer presupposes voluntary control and learnability. Chimpanzee vocalization (or its homologue in the common ancestor of chimpanzee and man) seems to represent a real precursor of human language.

The two commentaries appear supportive of the target article. Ujhelyi's commentary can be complemented with recent evidence supporting continuity of language and cognitive evolution in hominids. Gow & Rodkin's caveats regarding “pathonormal inference” and the single-case methodology are discussed from a developmental neurobiological perspective. Early structural brain lesion and developmental disorders can serve as pathological models of normal neurofunctional variability resulting from neurodevelopmental imprecision. A final point concerns the advantages of integrating multiple structural and functional imaging modalities in neuropsychological studies.

The major merit of Rose's book is the elaboration of the idea of multilevel causation in different explanatory languages. Yet Rose's critique of “ultra-Darwinism” is not convincing. Rose argues that activity and self-replication are properties of organisms rather than genes, which contradicts his idea of multilevel causation. Also, Rose fails to develop the concept of multilevel selection.

Many of Rose's criticisms of determinism in biology have clear relevance to modern cognitive and psychiatric science; too narrow a focus on the brain as an information processing machine runs the risk of neglecting the context in which information processing takes place, and too narrow a focus on the neuroscience of psychopathology runs the risk of neglecting other levels of explanation for these phenomena. It should be emphasized, however, that animal and genetic studies of phenomena of interest to cognitive and psychiatric science (e.g., Alzheimer's disorder, schizophrenia, attention deficit/hyperactivity disorder, and violence), while perhaps only providing a partial perspective, may be useful in understanding these phenomena and in leading to appropriate psychiatric interventions.

Rose's attack on ultra-Darwinists' and evolutionary psychologists' accounts of human behavior fails, largely because he does not offer a viable alternative. His “lifelines” view of organismic development is essentially an epigenetic one that few sociobiologists would disagree with, Rose seeks to disempower genes where human behavior is concerned, despite contrary neurogenetic evidence and at odds with the implications of his own lifelines view. He attempts to discredit biological determinist accounts by suggesting that their research program is politically motivated, while ignoring the scientific viability and novel insights such research has yielded.

Lifelines provides a useful corrective to “ultra-Darwinism” but it is marred by its failure to cite its scientific predecessors. Rose's argument could have been strengthened by taking greater account of the theory of autopoiesis in biology and of enactive cognitive science.

In reasserting the primacy of the individual in biological analysis, Rose directs attention away from the crucial insights of the developmental/structuralist perspective that he advocates. In presenting his advocacy as a diatribe, he brings disrespect down upon that very tradition.

Rose erroneously believes that the sciences of human behavior are being swept with a wave of genetic determinism. Actually, sociologists and psychologists remain predominantly hostile to any genetic influence on behavior. They will love Rose. The few behavior geneticists and sociobiologists in these disciplines are marginalized and looking for a little respect. Rose impugns their motives and ridicules their science.

Lifelines discusses two approaches to biology, “ultra-Darwinism” which Rose criticises, and the “homeodynamic perspective,” which he offers as an alternative. This review suggests that ultra-Darwinism is a caricature of the theoretical positions Rose wishes to oppose and that the homeodynamic perspective is not an alternative, but is complementary to so-called ultra-Darwinism.

Commentators are divided between those who welcome and creatively extend the agenda of Lifelines and those who defend what it criticises. My response covers style; history, politics, and ethics; concepts of freedom, active organisms, and determinism; the uses of metaphor; reductionism and levels of analysis; Darwin and Darwinists; heritability and intelligence; human universals and biological determinism.