Abstract
We investigated the quantity judgment abilities of two adult male western lowland gorillas (Gorilla gorilla gorilla) by presenting discrimination tasks on a touch-screen computer. Both gorillas chose the larger quantity of two arrays of dot stimuli. On some trials, the relative number of dots was congruent with the relative total area of the two arrays. On other trials, number of dots was incongruent with area. The gorillas were first tested with static dots, then with dots that moved within the arrays, and finally on a task where they were required to discriminate numerically larger subsets within arrays of moving dots. Both gorillas achieved above-chance performance on both congruent and incongruent trials with all tasks, indicating that they were able to use number as a cue even though ratio of number and area significantly controlled responding, suggesting that number was not the only relevant dimension that the gorillas used. The pattern of performance was similar to that found previously with monkeys and chimpanzees but had not previously been demonstrated in gorillas within a computerized test format, and with these kinds of visual stimuli.
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Acknowledgments
We are indebted to the Detroit Zoological Society (DZS), especially the Center for Zoo Animal Welfare, and to Cynthia Bennett for encouraging the collaboration between Oakland University and DZS. Without their support and assistance, these experiments could not have been conducted. The research was supported by NIH Grant HD060563 to MJB.
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Vonk, J., Torgerson-White, L., McGuire, M. et al. Quantity estimation and comparison in western lowland gorillas (Gorilla gorilla gorilla). Anim Cogn 17, 755–765 (2014). https://doi.org/10.1007/s10071-013-0707-y
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DOI: https://doi.org/10.1007/s10071-013-0707-y