Although many animals display bodily & behavioural changes consistent with the occurrence of affective states similar to those seen in humans, there is controversy about whether these are accompanied by conscious experiences

Towards a comparative science of emotion: Affect and consciousness in humans and animals. Elizabeth S. Paul et al. Neuroscience & Biobehavioral Reviews, November 26 2019. https://doi.org/10.1016/j.neubiorev.2019.11.014

Highlights
•    Emotions comprise conscious, behavioural, physiological and cognitive elements.
•    Neural correlates of conscious emotion can be investigated in humans and animals.
•    Contemporary theories of consciousness have differing implications for animals.

Abstract: The componential view of human emotion recognises that affective states comprise conscious, behavioural, physiological, neural and cognitive elements. Although many animals display bodily and behavioural changes consistent with the occurrence of affective states similar to those seen in humans, the question of whether and in which species these are accompanied by conscious experiences remains controversial. Finding scientifically valid methods for investigating markers for the subjective component of affect in both humans and animals is central to developing a comparative understanding of the processes and mechanisms of affect and its evolution and distribution across taxonomic groups, to our understanding of animal welfare, and to the development of animal models of affective disorders. Here, contemporary evidence indicating potential markers of conscious processing in animals is reviewed, with a view to extending this search to include markers of conscious affective processing. We do this by combining animal-focused approaches with investigations of the components of conscious and non-conscious emotional processing in humans, and neuropsychological research into the structure and functions of conscious emotions.

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8. Conclusions

The study of affective consciousness in animals falls squarely at the intersection of two longstanding controversies in psychological science – the relationship between consciousness and emotion and the measurement of nonhuman, and nonverbal, consciousness. Accordingly, the strands of empirical evidence and theoretical argument reviewed here are both richly diverse and hotly contested. But though it is beset by the twin enigmas of conceptualizing emotion and measuring consciousness, the study of animal affective consciousness is nonetheless of major potential importance, both for practical problems in animal welfare and for our efforts to get a clear view of our evolutionary kin, near and distant. We have adopted a componential view of emotions (reviewed in Section 3), in which conscious feelings constitute one component in a complex syndrome of related cognitive, motivational, expressive, and behavioural processes. And we have especially highlighted the implications of NCAC theories for a scientific understanding of how conscious feelings can, and cannot, empirically dissociate from other components of emotion, both within and across species.

In posing questions about conscious affect in animals, much (though not all1) work starts with the human case, where understanding is facilitated by subjects’ emotional reports (as well as the informal introspection the researcher employs in interpreting such reports). The human models are then used to identify candidate criteria for conscious emotion, which can be applied to observations of brain, behaviour, and physiology in different animal species. Research in this program can, in turn, be roughly divided into two classes – a wide-focus approach, which begins with general models of human consciousness (Section 4), and a narrow-focus approach, which sets out from specific models of human emotion (Section 5). The two approaches inform one another, because emotional consciousness is one form of consciousness, and together they can suggest principles for the identification of conscious affect in the absence of subjective report (Sections 6 and 7).

As our review illustrates, wide- and narrow-focus studies alike present a mixed picture of promising developments and enduring controversy. In our view, an especially promising strategy is to explicitly link proposed neurofunctional analyses of consciousness in general with a componential view of emotion in particular. This strategy is generative, suggesting novel potential resolutions to questions about conscious animal affect. Nonetheless, the stubborn persistence of core controversies (what kinds of cognition does consciousness require, and what kinds of emotional response require consciousness?) bars anything like a consensus choice among the candidate resolutions at present.

As an example of this dynamic, consider Fig. 1 and its depiction of the componential view of emotion. Here, five components of emotion (Scherer, 2005a,b) are conceptually distinguished, and the task for emotion researchers is to explain their empirical coordination in emotional responses. Such explanations may refer to hypothesized “coordinating mechanisms” that coherently control the component mechanisms (the solid lines in Fig. 1) and/or to direct links between the component mechanisms themselves (dashed lines). It is important to emphasize, however, that Fig. 1 does not, on its own, constitute a model of emotion. Rather, it supplies a conceptual framework within which empirical questions about emotion can be posed – questions which an adequate model, drawing on both wide- and narrow-focus empirical approaches, must answer. Most importantly: (1) how is the coordination of the different components of an emotional response achieved? And (2) do the various components – including emotional consciousness – play comparable or unequal roles in the process of cross-component coordination?

[Fig. 1. Componential framework for conceptualizing emotion. The five outer boxes depict component processes in emotion, similar to those identified in Scherer (2005a,b). The central box stands for possible central mechanisms (at cortical and/or subcortical levels) which may help to coordinate some or all of the components. Actions of the hypothetical central mechanisms are represented by solid lines, direct interactions between the five component processes by dashed lines.]

Different models of emotion, drawing on different views of the functional role(s) of consciousness, suggest different answers to these two critical questions. As an illustration, Fig. 2 shows how one model of conscious emotion, derived from a subset of the research reviewed here, would resolve these questions. In this model, a GW perspective on affective consciousness is assumed. That is, consciousness – affective and otherwise – is assumed to be linked to thalamocortical broadcasting of selected information for the flexible coordination of cognition and action. If consciousness is inherently linked to this coordination function, it will presumably be essential for some aspects of the coordination of component processes in human emotion. Returning to Fig. 1, this GW-inspired viewpoint would then suggest that the “coordinating mechanisms” are not neatly separable from the “consciousness” component. Rather, the consciousness component constitutes part of the coordinating mechanisms (though further unconscious mechanisms, specific to emotion, may also play a role in coordinating an emotional response). Fig. 2 shows how this neurofunctional model of conscious emotion unpacks and relates the “flat” uninterpreted relations in Fig. 1. In this way, the model offers one possible answer to the critical questions of how the emotion components relate to the coordinating process and to one another (consciousness, unlike the other components, is part of a posited central coordinating mechanism). It suggests, in turn, criteria for affective consciousness in the absence of subjective report (i.e. does the affective response reflect a level of integration and flexibility that requires the operation of the GW?).2

[Fig. 2. A possible neurofunctional interpretation of the componential framework. A GW model of conscious emotion is assumed for illustrative purposes. In this model, consciousness functions to globally integrate modular processors for the flexible control of cognition and action. On this view, consciousness is expected to play a central role in coordinating component processes, at least for those emotions which exhibit high levels of integration (i.e., responsiveness to a wide range of information inputs) and flexibility (i.e., adaptive sensitivity to a wide range of contexts). The model also allows for distinct unconscious coordinating mechanisms that may generate more stereotyped (aspects of) emotional responses.]

The model in Fig. 2 illustrates how a neurofunctional analysis of consciousness can flesh out the componential framework for emotion, implying conditions under which consciousness can(not) dissociate from the other emotion components, and hence providing principled criteria whereby consciousness can be inferred from observation of the other components. To be sure, the neurofunctional analysis of conscious emotion (a GW view) assumed in Fig. 2 is not the only available one, and it is not definitively established by the evidence reviewed here. Alternative (e.g., HOT) neurofunctional analyses may assign the consciousness component in Fig. 1 a more peripheral functional role, implying readier dissociability from other components, and hence requiring more stringent criteria for the identification of conscious feelings. At the other end of the spectrum, some views associate basic forms of consciousness (or sentience) with more elementary nervous system functions, implying that consciousness accompanies even component-responses with minimal complexity or coordination.

Nonetheless, the example illustrates the logic of leading approaches to the study of conscious emotion, highlighting both their promise and their limitations. On the one hand, developing theories of the NCAC suggest substantive interpretations of the componential framework, from which principled criteria for affective consciousness in nonverbal creatures can be derived. On the other hand, the search for NCACs itself remains closely bound up with longstanding controversies in the conceptualization of both consciousness and emotion. It is inseparable from fundamental questions, still not adequately resolved, about when, how, and why conscious experiences can be inferred from behavioural responses when subjective report is unavailable. The merging of a componential view of emotion with a neurofunctional analysis of consciousness thus opens up promising new paths toward a scientific understanding of animal affective consciousness, but also shines a sobering light on the obstacles that lie in their way.