Assessment of Representational Momentum in Monkeys Open Access

Hope, Jasmine Marie (2015)

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People overestimate the final location of a moving object in the direction of the trajectory of that object. This distortion in visual perception, known as Representational Momentum (RM), aids in anticipating the behavior of moving objects. Because humans read from left to right, the effect might be stronger when objects move rightward. We tested RM in nonhuman primates to investigate if RM is shared by a nonhuman primate relative in the absence of reading directionality. Five rhesus macaques (Macaca mulatta) were trained to touch the final location of an object that moved horizontally across a touch screen. If the object moved leftward, the object stopped in one of two locations on the left side of the screen and vice versa if the object moved rightward. The monkeys were presented with two choice boxes, one around the position of object disappearance and one to the right or left, until they picked the choice box where the object disappeared >80% of the time for 2 consecutive sessions. In Experiment 1, we tested for RM by measuring if the subjects overestimated the final location of the white square using probes in which the choice stimuli intersected at the center of object disappearance. RM would manifest as a higher ratio for subjects to pick the choice square further along the trajectory of the object. In humans, increasing speeds can increase RM, so in Experiment 2, the object speed varied in order to investigate if velocity influenced RM in nonhuman primates. If RM exists in monkeys, then subjects will choose a location further along the trajectory of a moving object more often than a location prior to the point of disappearance. There was not an apparent RM effect in either experiment. In the future, we will test orangutans and gorillas to determine if RM exists in our closest evolutionary relatives.

Table of Contents

Introduction Pages 1- 6

General Methods Pages 6-8

Experiment 1 Pages 8-10

Experiment 2 Pages 10-11

General Discussion Pages 11-15

References Pages 16-17

Figures Pages 18-28

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