This project addresses the problem of how to interpret claims of necessity, possibility, and counterfactuality used to characterize the relation of psychological to biological traits. Modal claims are increasingly made in the scientific context of comparative research mapping behavioral and psychological traits to phylogeny – for example, the hypothesis that neurons are necessary for simple forms of associative learning but that a brain or a nervous system is not. Modal claims also appear in the philosophical context of debates regarding the relation of consciousness to brains and artificial devices – for example, whether it is or is not possible for a system of artificial neurons to be conscious. However, the more we are able to investigate how psychological traits evolved and how these traits are related to evolved biological traits, the more we need to theorize their non-contingent relationships. For example, if only organisms with neurons can learn by association, then presumably these traits are not merely correlated. Similarly, if artificial neurons are in principle functionally equivalent to organic ones, we need to clarify what is biologically possible for the latter if our judgments of functional equivalence are to be scientifically-based rather than a matter of mere speculation. Understanding what is actually and counterfactually biologically possible for organic structures underlying subjective experience is critical for determining whether artificial substrates might realize any recognizable form of consciousness, or else realize something-we-know-not-what to which the label “consciousness” has been extended.

Biological modality is relatively undertheorized compared to physical modality and its applications have been restricted to topics entirely within biology, such as possible morphological configurations or the concept of evolvability. My project will extend its application to the psychology/biology interface. In particular, it will defend constraints on psychological possibility arising from biological traits. This view runs counter to the dominant metaphysics of mind and cognitive science in which psychological traits are not merely defined without explicit mention of the biological traits on which they (in some sense) depend but are barred in principle from having any necessary non-functional component. This principle not only makes it difficult to interpret the modal claims that are already being made. It also blocks defining a nested hierarchy of psychological characters partly in terms of specific structures needed to realize them, and from using homologies at multiple levels of biological organization to ground psychological homologies.

The modality issue is a key component of my overall research program to build on Tinbergen's evolution question for advanced cognition. The program’s primary motivation stems from the results of comparative research recent decades that now include many new species, new experimental paradigms, more extensive field work, and new targets of inquiry. These results have undermined longstanding views that advanced cognition and consciousness are unique endowments of H. sapiens. They also suggest that psychological traits, like other evolved traits, have a topology – they are not randoly distributed in phylogeny, Lorenz and Tinbergen pioneered conceptualizing behaviors in terms of phylogenetic characters, and we are now in a position to extend their theoretical insight to advanced cognitive abilities and conscious experience. Further progress on the evolution question for these traits requires adopting the conceptual tools that enable the use of cladistic methods in psychology, in particular the phylogenetic character concept.