Chimpanzees can visually perceive differences in the freshness of foods.

Tomoko Imura,Katsunori Okajima,Yuji Wada,Masaki Tomonaga,Tomohiro Masuda

doi:10.1038/srep34685

Abstract

Colour vision in primates is believed to be an adaptation for finding ripe fruit and young leaves. The contribution of the luminance distribution, which influences how humans evaluate the freshness of food, has not been explored with respect to the detection of subtle distinctions in food quality in non-human primates. We examined how chimpanzees, which are closely related to humans, perceive the freshness of foods. The findings suggest that chimpanzees were able to choose fresher cabbage based on both colour and grey-scale images. Additional tests with images of novel cabbage, spinach, and strawberries revealed that one chimpanzee could detect the freshness of other fruits and vegetables. The critical factor in determining the judgements of freshness made by the chimpanzees was the spatial layout of luminance information. These findings provide the first known evidence that chimpanzees discriminate between images representing various degrees of freshness based solely on luminance information.

Highlights

Colour vision in primates is believed to be an adaptation for finding ripe fruit and young leaves
The present findings show that chimpanzees discriminate between images based on luminance distribution only when images contain information pertaining to the 3-D structure of surfaces
This implies that luminance information of the spatial layout of surfaces contributes to chimpanzees’ determination of the freshness of the cabbage in the images

Summary

Introduction

Colour vision in primates is believed to be an adaptation for finding ripe fruit and young leaves. The critical factor in determining the judgements of freshness made by the chimpanzees was the spatial layout of luminance information These findings provide the first known evidence that chimpanzees discriminate between images representing various degrees of freshness based solely on luminance information. Murakoshi et al.[13] found that humans can adequately identify the level of degradation of individual food items by using the luminance distribution as a visual cue, even if the food items are observably different These studies show that luminance can provide important information, facilitating the perception of differences in the freshness of food. It remains unknown whether non-human primates can use the luminance distribution in an image to judge the quality of fruits and leaves. We analysed the effects of statistical information in the luminance distribution on the freshness judgements made by chimpanzees

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Conclusion