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Home / Equine Research Bank / Perception / Horses are sensitive to pictorial depth cues.
Perception1996; 25(9); 1121-1128; doi: 10.1068/p251121

Horses are sensitive to pictorial depth cues.

Abstract: In an attempt to demonstrate whether horses could make use of pictorial cues to depth, two were trained initially to make a relative-line-length discrimination between two lines placed one above the other. Psychophysical measurement of their discrimination thresholds showed that from a viewing distance of approximately 160 cm they could reliably distinguish a lower line of 10 cm from an upper one of 14 cm. In the second phase of the experiment, two lines of equal length were superimposed on a photograph of a set of railway tracks with many pictorial cues to depth, or a photograph of a pastoral scene with fewer obvious depth cues. To humans, the railway tracks created a Ponzo illusion, making the upper line-appear longer. When the horses were allowed to choose between the photographs, they overwhelmingly chose the display containing the converging railway tracks. Control experiments ruled out alternative explanations, leading to the conclusion that horses are susceptible to a Ponzo illusion created by depth cues in photographs.
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Publication Date: 1996-01-01 PubMed ID: 8983051DOI: 10.1068/p251121Google Scholar: Lookup
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  • Journal Article
  • Research Support
  • Non-U.S. Gov't

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The study investigates whether horses can perceive depth from flat images by using pictorial cues. It concludes that horses are indeed sensitive to these cues as they demonstrated susceptibility to the Ponzo illusion when presented with photographs including such depth indicators.

Initial Training and Discrimination Thresholds

  • The research started by training two horses to discriminate between two lines of different lengths, displayed one above the other.
  • The horses’ discrimination thresholds were measured using psychophysical methods. This involved determining their ability to reliably distinguish the length of two lines when viewed from around 160 cm away.
  • The results showed that the horses could reliably tell a lower line that was 10 cm long from an upper one that was 14 cm long.

The Experiment with Pictorial Cues

  • The second phase of the experiment involved superimposing two lines of equal length on two different photographs: one of a set of converging railway tracks with many pictorial cues indicating depth and the other of a pastoral scene with fewer obvious depth cues.
  • For humans, the image with the railway tracks normally creates a Ponzo illusion, which makes the upper line appear longer than the lower one even though they’re identical in length.
  • When the horses were then asked to choose between the two photographs, they overwhelmingly chose the one featuring the railway tracks. This suggests that the horses were also experiencing the Ponzo illusion, indicating a sensitivity to pictorial depth cues presented within the photograph.

Control Experiments

  • Control experiments were conducted to rule out alternative explanations for the horses’ noticeable preference for the image with the railway tracks.
  • These control experiments confirmed the initial conclusion: horses are susceptible to a Ponzo illusion created by depth cues in photographs.

Conclusion

  • From this research, horses were found to be sensitive to pictorial depth cues. They displayed an ability to compare the relative lengths of two lines and seemed to perceive depth within flat images, as indicated by their reactions to the Ponzo illusion.

Cite This Article

APA
Timney B, Keil K. (1996). Horses are sensitive to pictorial depth cues. Perception, 25(9), 1121-1128. https://doi.org/10.1068/p251121

Publication

Perception
ISSN: 0301-0066
NlmUniqueID: 0372307
Country: United States
Language: English
Volume: 25
Issue: 9
Pages: 1121-1128

Researcher Affiliations

Timney, B
  • Department of Psychology, University of Western Ontario, London, Canada. timney@sscl uwo.ca
Keil, K

    MeSH Terms

    • Animals
    • Depth Perception
    • Female
    • Horses
    • Optical Illusions
    • Psychophysics

    Citations

    This article has been cited 12 times.
    1. Ahsan T, Bolton K, Wilcox LM, Freud E. Perceived depth modulates perceptual resolution. Psychon Bull Rev 2022 Apr;29(2):455-466.
      doi: 10.3758/s13423-021-02006-8pubmed: 34585320google scholar: lookup
    2. Cappellato A, Miletto Petrazzini ME, Bisazza A, Dadda M, Agrillo C. Susceptibility to Size Visual Illusions in a Non-Primate Mammal (Equus caballus). Animals (Basel) 2020 Sep 17;10(9).
      doi: 10.3390/ani10091673pubmed: 32957449google scholar: lookup
    3. Feng LC, Chouinard PA, Howell TJ, Bennett PC. Why do animals differ in their susceptibility to geometrical illusions?. Psychon Bull Rev 2017 Apr;24(2):262-276.
      doi: 10.3758/s13423-016-1133-3pubmed: 27488557google scholar: lookup
    4. Tomonaga M, Kumazaki K, Camus F, Nicod S, Pereira C, Matsuzawa T. A horse's eye view: size and shape discrimination compared with other mammals. Biol Lett 2015 Nov;11(11).
      doi: 10.1098/rsbl.2015.0701pubmed: 26601679google scholar: lookup
    5. Rosa Salva O, Sovrano VA, Vallortigara G. What can fish brains tell us about visual perception?. Front Neural Circuits 2014;8:119.
      doi: 10.3389/fncir.2014.00119pubmed: 25324728google scholar: lookup
    6. Parrish AE, Beran MJ. When less is more: like humans, chimpanzees (Pan troglodytes) misperceive food amounts based on plate size. Anim Cogn 2014 Mar;17(2):427-34.
      doi: 10.1007/s10071-013-0674-3pubmed: 23949698google scholar: lookup
    7. Zivotofsky AZ, Goldberg ME, Powell KD. Rhesus monkeys behave as if they perceive the Duncker Illusion. J Cogn Neurosci 2005 Jul;17(7):1011-7.
      doi: 10.1162/0898929054475235pubmed: 16102233google scholar: lookup
    8. Miyashita Y, Nakajima S, Imada H. Differential outcome effect in the horse. J Exp Anal Behav 2000 Sep;74(2):245-53.
      doi: 10.1901/jeab.2000.74-245pubmed: 11029025google scholar: lookup
    9. Broseghini A, Bevilacqua V, Guérineau C, Mongillo P, Marinelli L. Effectiveness of shading and linear perspective cues in eliciting three-dimensional perception of bidimensional images in dogs. Anim Cogn 2025 Dec 29;29(1):5.
      doi: 10.1007/s10071-025-02026-0pubmed: 41460385google scholar: lookup
    10. Roth LSV, McGreevy P. Horse vision through two lenses: Tinbergen's Four Questions and the Five Domains. Front Vet Sci 2025;12:1647911.
      doi: 10.3389/fvets.2025.1647911pubmed: 40895790google scholar: lookup
    11. Broseghini A, Stasek M, Lõoke M, Guérineau C, Marinelli L, Mongillo P. Pictorial depth cues elicit the perception of tridimensionality in dogs. Anim Cogn 2024 Jul 22;27(1):49.
      doi: 10.1007/s10071-024-01887-1pubmed: 39037605google scholar: lookup
    12. Berardo C, Holland R, Schaffer A, Lopez Caicoya A, Liebal K, Valsecchi P, Amici F. Perception of optical illusions in ungulates: insights from goats, sheep, guanacos and llamas. Anim Cogn 2024 May 24;27(1):40.
      doi: 10.1007/s10071-024-01878-2pubmed: 38789595google scholar: lookup
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