Bridgemanian space constancy as a precursor to extended cognition

Abstract

A few decades ago, cognitive psychologists generally took for granted that the reason we perceive our visual environment as one contiguous stable whole (i.e., space constancy) is because we have an internal mental representation of the visual environment as one contiguous stable whole. They supposed that the non-contiguous visual images that are gathered during the brief fixations that intervene between pairs of saccadic eye movements (a few times every second) are somehow stitched together to construct this contiguous internal mental representation. Determining how exactly the brain does this proved to be a vexing puzzle for vision researchers. Bruce Bridgeman's research career is the story of how meticulous psychophysical experimentation, and a genius theoretical insight, eventually solved this puzzle. The reason that it was so difficult for researchers to figure out how the brain stitches together these visual snapshots into one accurately-rendered mental representation of the visual environment is that it doesn't do that. Bruce discovered that the brain couldn't do that if it tried. The neural information that codes for saccade amplitude and direction is simply too inaccurate to determine exact relative locations of each fixation. Rather than the perception of space constancy being the result of an internal representation, Bruce determined that it is the result of a brain that simply assumes that external space remains constant, and it rarely checks to verify this assumption. In our extension of Bridgeman's formulation, we suggest that objects in the world often serve as their own representations, and cognitive operations can be performed on those objects themselves, rather than on mental representations of them.

Keywords: Embodied cognition; Extended mind; Space constancy; Visual perception.