The Ebbinghaus illusion in a fish (Xenotoca eiseni)
- 876 Downloads
The tendency of fish to perceive the Ebbinghaus illusion was investigated. Redtail splitfins (Xenotoca eiseni, family Goodeidae) were trained to discriminate between two disks of different sizes. Then, fish were presented with two disks of the same size surrounded by disks of large or small size (inducers) arranged to produce the impression (to a human observer) of two disks of different sizes (in the Ebbinghaus illusion, a central disk surrounded by small inducers appears bigger than an identical one surrounded by large inducers). Fish chose the stimulus that, on the basis of a perception of the Ebbinghaus illusion, appeared deceptively larger or smaller, consistent with the condition of training. These results demonstrate that redtail splitfins tend to perceive this particular illusion. The results are discussed with reference to other related illusions that have been recently observed to be experienced by fish (such as the Navon effect), and with regard to their possible evolutionary implications.
KeywordsVisual perception Visual illusions Ebbinghaus illusion Titchener circles Fish
This study was supported by research grant from the Cassa di Risparmio of Trento e Rovereto. We wish to thank Matteo Kettmaier for his help with the experiments and Francesco Cerri for the maintenance of the aquaria.
Conflict of interest
The authors declare that they have no conflict of interest.
The experiments reported here comply with the current Italian and European Community laws for the ethical treatment of animals.
- Agrillo C, Miletto Petrazzini ME, Dadda M (2014) Illusory patterns are fishy for fish, too. Front Neural Circuits 7:137Google Scholar
- Ebbinghaus H (1902) Grundzüge der psychologie. Veit, LeipzigGoogle Scholar
- Fuss T, Bleckmann H, Schluessel V (2014) The brain creates illusions not just for us: sharks (Chiloscyllium griseum) can “see the magic” as well. Front Neural Circuits 20:8–24Google Scholar
- Oyama T (1960) Japanese studies on the so-called geometrical-optical illusions. Psychologia 3:7–20Google Scholar
- Sutherland NS, Mackintosh NJ (1971) Mechanisms of animal discrimination learning. Academic Press, LondonGoogle Scholar
- Vallortigara G (2006) The cognitive chicken: visual and spatial cognition in a non-mammalian brain. In: Wasserman EA, Zentall TR (eds) Comparative cognition: experimental explorations of animal intelligence. Oxford University Press, Oxford, pp 41–58Google Scholar
- Wade NJ (2005) Perception and illusions, historical perspectives. Springer, DordrechtGoogle Scholar
- Wade NJ (2010) Visual illusions. Corsini encyclopedia of psychology. Wiley, Hoboken, pp 1–2Google Scholar
- Winslow CN (1933) Visual illusions in the chick. Arch Physiol 153:1–83Google Scholar
- Wyzisk K (2005) Experimente zur Form- und Größenwahrnehmung beim Goldfisch (Carassius auratus) unter Verwendung von Scheinkonturen und Größentäuschungen. Ph.D. thesis, Johannes-Gutenberg-Universität Mainz, GermanyGoogle Scholar