Perception of Ebbinghaus–Titchener stimuli in starlings (Sturnus vulgaris)
Whether animals experience visual illusions is a fertile area of study for examining the evolution and operation of visual cognition across different species. Here, five starlings were tested to examine whether they experienced the Ebbinghaus–Titchener illusion. Across two experiments using an absolute target circle size discrimination, the size, similarity, distance, and number of the surrounding flankers were manipulated. The results suggest that this passerine species exhibits behavior inconsistent with the perception of the illusion, neither in a human-like fashion nor, as suggested by the first experiment, a reversed illusion. Instead, the typical training used to investigate this illusion caused the starlings to learn to integrate the irrelevant flankers into their decision process in a manner that precludes the study of illusory perception. The resulting discriminative behavior might best be described using a template-matching account. While illusion perception by animals remains an important comparative question, it requires additional validation to confirm the exact mechanisms of any illusory reports.
KeywordsStarling Visual illusions Comparative Psychophysics Size Perception
Parts of this research were supported by the National Eye Institute grant #RO1EY022655 to RGC. The authors would like to thank Suzanne Gray and Angelle Antoun for discussion and editing of this manuscript, as well as two anonymous reviewers for their comments. The data for this manuscript is stored in a digital repository, accessible from http://dx.doi.org/10.6084/m9.figshare.7664651.
- Chase S, Heinemann EG (2001) Exemplar memory and discrimination. In: Cook RG (Ed.), Avian Visual CognitionGoogle Scholar
- Feare C (1984) The starling. Oxford University Press, OxfordGoogle Scholar
- Husband S, Shimizu T (2001) Evolution of the avian visual system. In: Cook RG (Ed.), Avian visual cognition. www.pigeon.psy.tufts.edu/avc/husband/
- Marr D (1982) Vision. Freeman, San FranciscoGoogle Scholar
- Parrish AE, Brosnan SF, Beran MJ (2015) Do you see what I see? A comparative investigation of the Delboeuf illusion in humans (Homo sapiens), rhesus monkeys (Macaca mulatta), and capuchin monkeys (Cebus apella). J Exp Psychol Anim Learn Cogn 41(4):395–405. https://doi.org/10.1037/xan0000078 CrossRefPubMedPubMedCentralGoogle Scholar
- Shimizu T, Watanabe S (2012) The avian visual system. In: Lazareva OF, Shimizu T, Wasserman EA (eds) How animals see the World. Oxford University Press, New York, pp 473–482Google Scholar