I argue that a critical feature of language that distinguishes it from animal communication isdisplacement,the means to communicate about the non-present. This implies a capacity for mental travels in time and space, which is the ability to call to mind past episodes, imagine future ones or purely fictitious ones, and locate them in different places. While mental travel in time, in particular, is often considered to be unique to humans, behavioral and neurophysiological evidence suggests that it is evident in some (...) form, at least, in nonhuman animals, including rodents, and may go far back in the evolution of animals that move. The linguistic capacity to share experiences that transcend space and time evolved much more recently, accelerating during the Pleistocene with increasing demands for effective cooperation and long-distance planning. The expansion of mental time travel probably co-evolved with the development of language itself, because the sharing of memories, plans, and stories vastly added to our own individual experiences. From this perspective, the critical period of the Road Map runs from the emergence of the genusHomoaround 2 million years ago to the present. (shrink)

This paper is a commentary on the target article by Michael Arbib, “Levels of modeling of mechanisms of visually guided behavior”, in the same issue of the journal, pp. 407–465. -/- I focus on the importance of the inclusion of an ability of a system to entertain, at a given time, multiple instantiations of a given schema (situation template, frame, script, action plan, etc.), and complications introduced into neural/connectionist network systems by such inclusion.

Intermediate constructs are required as bridges between complex behaviors and realistic models of neural circuitry. For cognitive scientists in general, schemas are the appropriate functional units; brain theorists can work with neural layers as units intermediate between structures subserving schemas and small neural circuits.After an account of different levels of analysis, we describe visuomotor coordination in terms of perceptual schemas and motor schemas. The interest of schemas to cognitive science in general is illustrated with the example of perceptual schemas in (...) high-level vision and motor schemas in the control of dextrous hands.Rana computatrix, the computational frog, is introduced to show how one constructs an evolving set of model families to mediate flexible cooperation between theory and experiment. Rana computatrix may be able to do for the study of the organizational principles of neural circuitry what Aplysia has done for the study of subcellular mechanisms of learning. Approach, avoidance, and detour behavior in frogs and toads are analyzed in terms of interacting schemas. Facilitation and prey recognition are implemented as tectal-pretectal interactions, with the tectum modeled by an array of tectal columns. We show how layered neural computation enters into models of stereopsis and how depth schemas may involve the interaction of accommodation and binocular cues in anurans. (shrink)