Assessing Ecological Advantages to Color Vision and Color Blindness in Capuchin Monkeys Under Controlled Conditions Open Access

Abstract

Prior research into Sapajus [Cebus] apella (capuchin monkey) color vision has established that some females and all males are dichromats (red-green colorblind), while other females are trichromats (full color vision). One proposed trichromat advantage is in fruit foraging, while a proposed dichromat advantage is in hunting cryptic prey. This study, composed of two dichotomous choice tasks, intended to determine if these hypotheses, supported by previous observational studies, are still apparent in a controlled environment without other sensory/social cues. The first task was designed to determine if color vision influences efficiency in identifying red objects in green images. The second was designed to determine if color vision influences the ability to identify objects in red-green camouflaged images. Many subjects were unable to pass the training stages, including most males, so we were unable to make an overall comparison between sexes. However, females displayed an overall preference for images with red apples on green backgrounds over green apples on green backgrounds, while the one male tested showed no preference, supporting a trichromat ability in finding red objects on green backgrounds. The training data also supports a trichromat advantage over dichromats found in the literature, though we require genotype data or more male data to strengthen this claim. Results of the camouflage task indicates a floor effect, suggesting that the task may have been too complex to assess the effects of color vision on camouflage effectiveness.

Table of Contents

I.         Abstract………………………………………………………………………….3

II.         Introduction……………………………………………………………...………4

III.         Methods……………………………………………………………………..…...8

a.     Participants……………………………………………………..………..8

b.     Procedure………………………………………………………..……….9

                                      i.     Color Contrast Task………………………………………….…11

                                     ii.     Color Camouflage Task…………………………………….…..12

                                     iii.     Stimuli Adjustments………………………………………...…..13

c.     Scoring and Data Reduction……………………………………...……..14

d.     Analysis…………………………………………………………...…….14

                   IV.         Results…………………………………………………………………….…….16

a.     Color Contrast Task……………………………………………..………16

b.     Color Camouflage Task…………………………………………………20

                     V.         Discussion……………………………………………………………………….23

a.     Color Contrast Task……………………………………………..………23

b.     Color Camouflage Task…………………………………………………26

c.     Future Directions………………………………………………………..28

                   VI.         References……………………………………………………………………….29

About this Honors Thesis

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School	Emory College
Department	Psychology
Subfield / Discipline	Neuroscience and Animal Behavior
Degree	B.A.
Submission	Honors Thesis
Language	English
Research Field	Psychology, Behavioral Sciences Biology, Zoology Psychology, Psychobiology
Keyword	ecology color vision
Committee Chair / Thesis Advisor	Brosnan, Sarah, Georgia State University Wilson, Ben, Emory University
Committee Members	Dilks, Daniel, Emory University Benitez, Marcela, Emory University

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