Stimulus characteristics, learning bias and visual discrimination in zebrafish (Danio rerio)

• Published in: Behavioural processes Vol. 192; p. 104499
• Main Authors: Santacà, Maria, Dadda, Marco, Miletto Petrazzini, Maria Elena, Bisazza, Angelo
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.11.2021
• Subjects: brain; cognition; color; Danio rerio; Discrimination learning; Fish cognition; Learning constrains; Zebrafish; Zebrafish; Discrimination learning; Learning constrains; Fish cognition
• ISSN: 0376-6357; 1872-8308; 1872-8308
• DOI: 10.1016/j.beproc.2021.104499

•Previous studies suggest limited discrimination learning abilities in zebrafish.•High learning performance was observed using outlined figures as stimuli.•In colour, shape, and size discrimination zebrafish compared to higher vertebrates.•Subjects exhibited strong stimulus bias, but only in tasks with filled figures.•As for other vertebrates, mirror-image discrimination was the most difficult. Zebrafish is an emerging model in the study of brain function; however, knowledge about its behaviour and cognition is incomplete. Previous studies suggest this species has limited ability in visual learning tasks compared to other teleosts. In this study, we systematically examined zebrafish’s ability to learn to discriminate colour, shape, size, and orientation of figures using an appetitive conditioning paradigm. Contrary to earlier reports, the zebrafish successfully completed all tasks. Not all discriminations were learned with the same speed and accuracy. Subjects discriminated the size of objects better than their shape or colour. In all three tasks, they were faster and more accurate when required to discriminate between outlined figures than between filled figures. With stimuli consisting of outlines, the learning performance of zebrafish was comparable to that observed in higher vertebrates. Zebrafish easily learned a horizontal–vertical discrimination task, but like many other vertebrates, they had great difficulty discriminating a figure from its mirror image. Performance was more accurate for subjects reinforced on one stimulus (green over red, triangle over circle, large over small). Unexpectedly, these stimulus biases occurred only when zebrafish were tested with filled figures, suggesting some causal relationship between stimulus preference, learning bias and performance.