Trained goldfish have the ability to accurately estimate the distance they had swam, reveals a new study* from the University of Oxford.

Dr Adelaide Sibeaux, who led the study, trained nine goldfish to swim a distance of 70 cm within a narrow tank covered with a repeating pattern of vertical stripes every 2 cm. Upon reaching the set distance, the fish were prompted by an external cue to turn around and swim back.

Once the cue was removed, eight of the nine fish accurately estimated the set distance to turn around, swimming an average distance of 74 cm. The fish continued to swim the 70 cm even when their start position was shifted 20 or 40 cm forwards.

Dr Sibeaux said that the study presents robust evidence that goldfish can accurately estimate distance and show that they use optic flow to do so.

“These results provide a compelling basis to use goldfish as a model system to investigate the evolution of the mechanisms that underpin spatial cognition in vertebrates.”

The researchers believe that goldfish estimate distances by visually streaming the apparent motion patterns of objects in the environment, known as optic flow. Humans and other terrestrial animals estimate distances by measuring how the angle between their eye and surrounding objects change as they travel.

*Adelaide Sibeaux, Cecilia Karlsson, Cait Newport, Theresa Burt de Perera. Distance estimation in the goldfish ( Carassius auratus )Proceedings of the Royal Society B: Biological Sciences, 2022; 289 (1984) DOI: 10.1098/rspb.2022.1220

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