Guppies learn faster to discriminate between red and yellow than between two shapes

Abstract

Animal species are expected to evolve specialised cognitive abilities to solve the tasks that are critical for their fitness. The literature contains several examples of specialised cognitive abilities, but few regard fish. The guppy, Poecilia reticulata, is a freshwater fish in which females choose their mates based on colouration, and orange‐coloured fruits are important diet enrichments for both sexes. For these reasons, we expect that this species has evolved enhanced learning abilities in colour discrimination compared to other types of discrimination. The comparison between studies in which guppies were tested for colour discrimination and studies in which guppies were tested for shape discrimination seems to support this hypothesis, but direct testing is still lacking. We experimentally compared the learning performance of guppies trained in a red–yellow colour discrimination learning task and that of guppies trained in a shape discrimination learning task using the same, automated conditioning procedure. Guppies trained in the colour discrimination showed greater learning performance, which provides support to the hypothesis that guppies possess enhanced colour discrimination abilities. Moreover, we found that male guppies performed better than females in both shape and colour discrimination learning.

Plastic changes in brain morphology in relation to learning and environmental enrichment in the guppy (Poecilia reticulata)

“…In the case of the reversal-learning experiment, forward learning in the form of distinguishing between two distinct colours could be a fairly easy task. Taking into consideration the natural behaviour of wild guppies, females are often faced with situations involving some aspect of colour discrimination as in the case of foraging and mate choice (Lucon-Xiccato et al, 2019). Given this innate ability to distinguish between colours, successful learning in the associative learning phase may not necessarily require extensive cognitive capabilities.…”

Poor numerical performance of guppies tested in a Skinner box

“…Subjects were adult guppies from an ornamental strain ("snakeskin cobra green") breed at the Department of General Psychology of University of Padova. This population was the same as used in the recent studies conducted in our laboratory on Skinner-box training as well as on numerical abilities 9,16 . We trained 6 guppies, a sample size similar to that of prior studies on fish trained numerical abilities 9,15 .…”

“…We used an automatic conditioning chamber similar to that described in detail elsewhere 16,17 (Fig. 1).…”

“…We recently developed a Skinner box-like operant conditioning chamber for fish, equipped with a computerized system that tracks the movements of the subject and delivers small amounts of food upon a correct response 16 . Tested with this chamber, guppies can easily perform 80 reinforced trials per session and show excellent performance in colour discrimination, reaching a 90-95% accuracy in 2-3 sessions 16 .…”

“…We recently developed a Skinner box-like operant conditioning chamber for fish, equipped with a computerized system that tracks the movements of the subject and delivers small amounts of food upon a correct response 16 . Tested with this chamber, guppies can easily perform 80 reinforced trials per session and show excellent performance in colour discrimination, reaching a 90-95% accuracy in 2-3 sessions 16 . To test the hypothesis that part of the perceived gap between fish and homeotherms could be due to the use of automatic training procedures in the latter, we studied visual numerosity discrimination in guppies using the aforementioned Skinner box.…”