# Visual Discrimination Task in Guppies Using a Simultaneous Matching-to-Sample Procedure

## TL;DR

Guppies can successfully complete a visual discrimination task, showing they can recognize and match stimuli based on visual features.

## Contribution

This study demonstrates guppies' ability to perform a simultaneous matching-to-sample task with multiple visual stimuli.

## Key findings

- Guppies learned to select the correct stimulus in a limited number of trials.
- Performance improved when multiple stimuli were used, suggesting better generalization.
- Guppies succeeded in all experiments, including those with complex geometric shapes.

## Abstract

When it comes to making quick decisions based solely on a few visual features, fish have been shown in the literature to be, in general, skilled decision-makers. In this study, we investigated how fish are able to recognize two stimuli as identical while discarding a third one. We started by using basic features such as color and shape, and then assessed the same ability using a set of twelve different geometric figures. Although the fish were successful in all three tasks, they performed particularly well as the complexity increased, suggesting a strong ability to abstract essential visual features and use them to their advantage. Matching to sample is a tool that allows for a precise assessment of our ability to detect similarities and differences in a cognitive task. Identifying this ability in animal organisms helps us better understand the perceptual rules that guide visual behavior.

Cognitive abilities in fish have been widely demonstrated using experimental protocols commonly adopted with mammals and birds. Only a few studies have tested fish in the simultaneous match-to-sample task (sMTS), and mixed evidence regarding their capacity to solve the task has been reported. Here we investigated whether guppies (Poecilia reticulata) could discriminate stimuli based on their sameness in the sMTS where fish presented with a sample stimulus had to choose which of two simultaneously presented comparison stimuli matched it. We also assessed how performance was influenced by the training set size and stimulus type. Three experiments were conducted using three different sets of stimuli: two colors (red and green), two geometric shapes (circle vs. triangle); and multiple shapes. Performance was analyzed using binomial tests, t-tests, and generalized linear mixed models. The results showed that guppies learned to select the rewarding stimulus in a relatively limited number of trials and were successful in all experiments. Although no effect of the training set size was observed, guppies were more accurate when multiple stimuli were used. These findings support previous evidence suggesting that multiple training stimuli may improve generalization abilities and set the basis for future studies that adopt a delayed version of the task.