Evolved navigation theory and the environmental vertical illusion
Abstract
These studies suggested that everyday visual perception is unconsciously subject
to large-scale illusions on ubiquitous environmental surfaces. Participants overestimated
environmentally vertical surfaces and did so to an increasing degree with longer surfaces,
neither of which occurred with environmentally horizontal surfaces. I title this illusion
the environmental vertical illusion. The severity of previous injury from a fall related to
the degree of illusion such that more severe previous falling injuries were associated with
lower illusion magnitudes, even though the illusion is still present at higher injury
severities. I predicted these data from hypotheses derived from Evolved Navigation
Theory (ENT), which focuses on how navigational costs over evolutionary time can
shape cognitive and perceptual mechanisms.
Virtual reality data suggested that unrealistically artificial falling costs failed to
produce the environmental vertical illusion, even on apparently vertical surfaces. Virtual
reality methods also suggested that distance estimation from immobile visual displays
deviated from natural distance estimation in important ways that hold implications for
tasks involved in piloting and surgery. Data from physical and virtual reality suggested
that no clear relationship existed between the 2D Vertical-Horizontal Illusion and 3D
distance estimates gathered here.
The current findings hold implications outlined under ENT for areas such as
anxiety disorders, piloting, surgery, individual differences, and visual stimuli design.
However, these findings may be most important because distance and orientation
perception occurs constantly in most visual systems and, consequently, most behaviors.
Understanding how distance perception occurs thus helps us to understand one of the
most common of all psychological experiences. These data suggest that a primary
component of human visual experience is illusory. However, through the use of a theory
rooted in evolution (ENT), we may be able to predict and better understand these
important features of human psychology.
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