Paper, Perception of biological motion by jumping spiders

This pattern, termed “biological motion” in the literature, can
be used as a visual cue, enabling many animals (including humans) to distinguish animate
from inanimate objects. Crucially, even artificially created scrambled stimuli, with no recognizable
structure but that maintains semirigid movement patterns, are perceived as animated.
However, to date, biological motion perception has only been reported in
vertebrates. Due to their highly developed visual system and complex visual behaviors, we
investigated the capability of jumping spiders to discriminate biological from nonbiological
motion using point-light display stimuli. These kinds of stimuli maintain motion information
while being devoid of structure. By constraining spiders on a spherical treadmill, we simultaneously
presented 2 point-light displays with specific dynamic traits and registered their preference
by observing which pattern they turned toward. Spiders clearly demonstrated the
ability to discriminate between biological motion and random stimuli, but curiously turned
preferentially toward the latter. However, they showed no preference between biological
and scrambled displays, results that match responses produced by vertebrates. Crucially,
spiders turned toward the stimuli when these were only visible by the lateral eyes, evidence
that this task may be eye specific. This represents the first demonstration of biological
motion recognition in an invertebrate, posing crucial questions about the evolutionary history
of this ability and complex visual processing in nonvertebrate systems.

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