Abstract
The detectability of luminance-modulated grating patches was determined for 4 adult chimpanzees. For efficient measurements of contrast thresholds, an adaptive psychophysical measurement, PEST (Parameter Estimation by Sequential Testing), was used in chimpanzees behavioral experiment. In the detection task for a 0.5 c/deg horizontal Gabor-type patch, consistency and reliability of the estimated thresholds in the procedure were evaluated in comparison with the data collected in the method of constant stimuli. Chimpanzees showed very small between-session variances of threshold values, which were well-matched to those estimated in the method of constant stimuli. After assessing validity of PEST method in chimpanzees, contrast sensitivity functions were obtained over the range of 0.5 – 8.0 c/deg using the Gabor patches. The contrast sensitivity was similar to that of humans, showing bandpass shape functions with both low and high frequency attenuation. These results suggest that humans and chimpanzees share the physiological mechanisms underlying spatial vision.
This study was financially supported by Grants-in-Aid for Scientific Research (12002009, 16002001, 13610086 and 16300084) and for the 21st Century COE Program (D2) from the Ministry of Education, Culture, Sports, Science, and Technology of Japan, and also supported by Research Fellowship (16/1060) from the Japan Society for the Promotion of Science for Young Scientists.