The PROUST hypothesis: the embodiment of olfactory cognition

The extension of cognition beyond the brain to the body and beyond the body to the environment is an area of debate in philosophy and the cognitive sciences. Yet, these debates largely overlook olfaction, a sensory modality used by most animals. Here, I use the philosopher's framework to explore the implications of embodiment for olfactory cognition. The philosopher's 4E framework comprises embodied cognition, emerging from a nervous system characterized by its interactions with its body. The necessity of action for perception adds enacted cognition. Cognition is further embedded in the sensory inputs of the individual and is extended beyond the individual to information stored in its physical and social environments. Further, embodiment must fulfill the criterion of mutual manipulability, where an agent's cognitive state is involved in continual, reciprocal influences with its environment. Cognition cannot be understood divorced from evolutionary history, however, and I propose adding evolved, as a fifth term to the 4E framework. We must, therefore, begin at the beginning, with chemosensation, a sensory modality that underlies purposive behavior, from bacteria to humans. The PROUST hypothesis (perceiving and reconstructing odor utility in space and time) describers how olfaction, this ancient scaffold and common denominator of animal cognition, fulfills the criteria of embodied cognition. Olfactory cognition, with its near universal taxonomic distribution as well as the near absence of conscious representation in humans, may offer us the best sensorimotor system for the study of embodiment.

Morph-specific life-history correlations in a wing-dimorphic water strider

Life-history theory predicts a negative correlation between reproduction and survival because individuals differ in their investment in early reproduction at the expense of survival. However, life-history trade-offs can be masked when individual differences in resource allocation are smaller than those in resource acquisition. In polymorphic species, as distinct morphs exhibit differences in intrinsic physiology, the relative effects of resource acquisition and allocation on life-history traits will differ between morphs, contributing to morph-specific life-history correlations. Here, in the wing-dimorphic water strider Aquarius paludum, we found that wing morphs differed in within-morph individual-level life-history correlations. Longer-lived flight-capable long-winged females produced fewer eggs per day and matured later, whereas life-history trade-offs were not observed in short-winged flightless females. The survival-reproduction trade-off observed in long-winged females may be a result of individual differences in the timing of wing muscle histolysis. Individuals that underwent wing histolysis early would have increased reproduction at the expense of a shorter life, whereas individuals with late wing histolysis would have reduced reproduction but a longer life. Short-winged females, who never develop wings, effectively have more resources to allocate to both survival and reproduction, masking any life-history trade-offs. Thus, we suggest that morph-specific effects of resource allocation trade-offs can shape the morph-specific extent of individual variation in life-history strategies, which may contribute to the evolution and maintenance of within-species polymorphism.