Submitted Successfully!
To reward your contribution, here is a gift for you: A free trial for our video production service.
Thank you for your contribution! You can also upload a video entry or images related to this topic.
Version Summary Created by Modification Content Size Created at Operation
1
Michael Beran
 -- 2320 2023-01-07 13:29:03 |
2 format
Jason Zhu
 + 1 word(s) 2321 2023-01-09 02:56:03 | |
3 format
Jason Zhu
 -62 word(s) 2259 2023-02-14 09:25:18 |

Video Upload Options

Do you have a full video?
Send video materials Upload full video

Confirm

Are you sure to Delete?
Yes No
Cite
If you have any further questions, please contact Encyclopedia Editorial Office.
Beran, M.J.;  Parrish, A.E. Consistently Inconsistent Perceptual Illusions in Nonhuman Primates. Encyclopedia. Available online: https://encyclopedia.pub/entry/39864 (accessed on 04 July 2024).
Beran MJ,  Parrish AE. Consistently Inconsistent Perceptual Illusions in Nonhuman Primates. Encyclopedia. Available at: https://encyclopedia.pub/entry/39864. Accessed July 04, 2024.
Beran, Michael J., Audrey E. Parrish. "Consistently Inconsistent Perceptual Illusions in Nonhuman Primates" Encyclopedia, https://encyclopedia.pub/entry/39864 (accessed July 04, 2024).
Beran, M.J., & Parrish, A.E. (2023, January 07). Consistently Inconsistent Perceptual Illusions in Nonhuman Primates. In Encyclopedia. https://encyclopedia.pub/entry/39864
Beran, Michael J. and Audrey E. Parrish. "Consistently Inconsistent Perceptual Illusions in Nonhuman Primates." Encyclopedia. Web. 07 January, 2023.
Consistently Inconsistent Perceptual Illusions in Nonhuman Primates
Edit
This entry is adapted from the peer-reviewed paper 10.3390/ani13010022

Visual illusions fascinate humans, in large part because we realize how such experiences disconnect how we perceive the world from reality. The discovery that other animals also experience some of these illusions has provided a compelling comparative story about the role that perception plays in sometimes misrepresenting the nature of the real world. What has also become apparent from comparative studies is that not all animals experience illusions the same way, and sometimes the same individual may not experience some illusions while experiencing others.

illusions individual differences vision primates

1. Introduction

Perceptual illusions fascinate humans. They are omnipresent in the modern world. Visual illusions are popular on social media platforms, where there are yearly articles on the best illusions from that year [1], and where one finds endless debate about what people think they may see, and why it is so fascinating (and frustrating) that others do not see the same thing (e.g., is the dress blue or gold? [2]). Beyond entertainment, illusions are often featured in scientific settings for the public (for example, the Fernbank Museum of Natural History in Atlanta has featured an exhibit on sensory experience and perceptual illusions for many years), and they are even a part of the educational system for many children.
Perceptual illusions serve a purpose beyond entertaining people as as they also help researchers understand the constraints of the perceptual experience, and they inform people about how other cognitive mechanisms interact with sensation and perception to generate such experiences [3]. Although perceptual illusions are “errors in the machine,” they also are tools for understanding how that machine works more broadly, in the same way that decision-making errors and biases inform people about how researchers frame decisions and calculate the value of options. The ancient Greeks considered the causes and implications of perceptual illusions (e.g., Aristotle and the waterfall effect), and the first scientific description of an illusion was carried out by Necker [4], followed by numerous other descriptions of illusions shortly after [5][6]; for a review, see [7]. Central to many of these early experiments was an appreciation of individual differences in how people experienced illusions, although formal assessments of what accounted for those differences often was not undertaken.
Given this widespread interest in perceptual illusions among humans, combined with the fascination about the minds of other animals, it is no surprise that studying illusory experiences across species has been a longstanding area of focus in comparative psychology and ethology [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. Although studies of illusory experiences have been conducted with many species, researchers focus the attention on nonhuman primates, simply for the reason that researchers know more about those species than others, and because nonhuman primates have been among the most extensively tested species. They highlight specific studies from the laboratory that included tests with rhesus monkeys (Macaca mulatta) and capuchin monkeys (Sapajus apella), sometimes in comparison to nearly identical tests given to human adults and human children. The goal in focusing on that work is not to downplay or ignore the many other creative and informative studies of other primates or non-primate species [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23], but to show that even in a restricted sample, some important points emerge about the need to assess and try to account for individual differences in these illusory experiences. Those differences are present and are often acknowledged and reported in empirical studies, even if there is little attempt made to explain why those differences exist. Some of the earliest papers in comparative psychology made this clear. For example, when chicks were given four tests of different illusions, it was noted in the abstract of that report that marked individual differences in susceptibility were shown for all four of the illusions [8]. However, there was no indication of what accounted for these differences.
Such individual differences likely offer substantial insight into the nature of perceptual processing mechanisms, not for their universality of operation, but for the way in which those mechanisms interact with variables such as species membership, age, sex, foraging ecology, attentiveness, and the prioritization of so-called top-down versus bottom-up processing of stimulus properties. Although there is still excellent value in charting what new species may be susceptible to different illusory experiences, so as to broaden the phylogenetic map of such experiences, there is equal value in trying to understand why some individuals experience illusions whereas others do not. Additionally, there is great value in understanding why even the same individual may be susceptible to some illusory experiences but not others.

2. Visual Illusions Research

Data were drawn from published papers from the Language Research Center at Georgia State University that included rhesus monkeys and/or capuchin monkeys, and that specifically focused on one or more geometric visual illusions. Researchers included any papers that had one or more primate subjects in them who also were subjects in at least three other experiments from the laboratory that assessed perceptual illusion susceptibility. Any included papers had to report the specific performances of each subject with regards to the illusory outcome (e.g., misperceiving item size or relative quantity), so that researchers could assign a positive or negative value to that subject for that illusory experience. Researchers chose to classify each subject as either “showing the illusion” or not, rather than trying to quantify the magnitude of the illusion, because the latter effort would have excluded a large number of these papers, and researchers wanted a larger sample size. This resulted in a total of 10 studies and 14 individual experiments, each of which is described in the linked paper (along with examples of these visual illusions). Across all experiments, a total of 8 rhesus monkeys and 10 capuchin monkeys met criterion for inclusion in this summary by participating in at least four experiments.
Table 1 shows the results of this qualitative survey. Not a single monkey was susceptible to all illusory stimuli to which they were exposed. At the other extreme, one monkey (Hank) showed susceptibility in only one of the nine experiments in which he participated. All other monkeys showed susceptibility to some but not all illusions, and many of them showed susceptibility about half of the time. For those studies in which two experiments were conducted, providing a conceptual replication within-study, there were also changes in susceptibility for the monkeys. In Agrillo et al. [24], only 1 of 13 monkeys replicated their susceptibility in both experiments. In Agrillo et al. [25], only two of six monkeys showed the illusory effect in both experiments. In Parrish et al. [26], only one monkey (Gale) showed the illusory effect in both experiments, and in Parrish and Beran [27], three of five monkeys replicated the illusory outcome. These qualitative results make clear the variability across illusions within this sample of monkeys, and also the variability within individuals not only for different illusions, but also for the same illusion tested at different times.
Table 1. Susceptibility of each monkey in each experiment in terms of experiencing the illusion in the same direction as for humans.
Monkey Agrillo
et al.,
2014a		 Agrillo
et al., 2014b
Exp 2		 Agrillo et al., 2014b Exp 3 Agrillo
et al.,
2015
Exp 1		 Agrillo
et al.,
2015
Exp 4		 Parrish
et al.,
2015
Exp 1		 Parrish
et al.,
2015
Exp 2		 Parrish
et al.,
2016
Exp 1		 Parrish
et al.,
2019		 Agrillo
et al.,
2019		 Parrish
et al.,
2020		 Parrish & Beran 2021
Exp 1		 Parrish & Beran 2021
Exp 2		 McKeon
et al.,
2022
Macaques                            
Chewie   YES NO     NO YES   YES No   YES NO NO
Gale   YES NO YES NO YES YES              
Han   YES YES     NO YES   YES No   NO ^ NO ^ NO
Hank   NO NO YES NO NO NO ^   NO NO       NO
Lou YES     YES YES NO YES   NO NO   YES YES NO
Luke YES NO NO YES YES       NO NO       NO
Murph YES NO YES NO YES NO YES   NO NO   YES YES NO
Obi       NO NO NO YES   YES NO   YES YES NO
Capuchins                            
Gonzo *           NO YES YES NO NO        
Gretel *           NO YES YES NO NO        
Griffin   YES NO     NO YES   NO NO YES      
Liam   NO NO     NO ^ YES   NO NO YES      
Logan   YES NO ^     NO ^ YES   YES NO NO      
Mason           NO ^ YES NO NO NO        
Nala *   NO NO     NO ^ NO ^   NO NO YES      
Nkima   YES NO     NO YES   NO ^ NO NO      
Widget *   NO NO           YES NO YES      
Wren *   YES NO     NO YES   YES NO YES      
In an unpublished study from a laboratory conducted with adult humans (college students), a similar pattern was found. Researchers presented 46 participants with the Delboeuf illusion (hereafter DBI; [28]) and the Ebbinghaus illusion (hereafter EBI; [29]) in the context of having those participants adjust an onscreen dot until they thought it matched the size of a comparison stimulus presented in an illusory context (Figure 1a,b). Although most participants had a tendency to overestimate the size of the dot presented in a small surrounding circle for the DBI and the size of the dot centered among small surrounding circles in the EBI, there were individuals who did not show this typical susceptibility. The relation of the magnitude of DBI and EBI susceptibility in this sample was nonsignificant, r(44) = 0.23, p = 0.12, and it accounted for only 5.3% of the variance in the sample (Figure 1c). As with the monkeys, humans are variable in their susceptibility to closely related illusory experiences, even within the same task given at the same time to the same people.
Animals 13 00022 g002 550
Figure 1. The Delboeuf (a) and Ebbinghaus (b) illusions in which the central dots surrounded by a smaller perimeter ring or a series of smaller other dots (i.e., the right stimuli in each image) are overestimated relative to when the surrounding ring or series of circles are large. The relative susceptibility to each of these illusions in a sample of 46 adult humans where positive values indicate the typical illusory experience (c).

3. Discussion

The take-home message of the brief survey of a sample of primates, given a moderate range of perceptual illusory experiences, is that there was a “consistent inconsistency” in their susceptibility to such illusions. Across these studies, rarely did any specific primate experience most or all illusions. Rather, the majority of these monkeys sometimes responded as if they experienced a given illusion, although across multiple tests of the same or similar illusions, there was variability at the level of the individual. Additionally, this pattern matched that of an unpublished sample of human participants given two well-known illusions, the Delboeuf illusion and the Ebbinghaus illusion, even though those two illusions were presented within the same task, using the same computerized apparatus. It also matched the consistent reports of large-scale studies with humans in which there were large individual differences in susceptibility [30][31][32][33][34].
There are a number of reasons why illusory experiences in nonhuman animals (and humans) may be consistently inconsistent. One strong candidate for accounting for difference across illusions (and studies) is methodological variation. How individuals are trained to perform tasks, how stimuli are created and presented, and what form responses take in tasks all could affect inconsistencies in experiencing illusions across studies (see [35][36][37]). Recognizing the relative priority of global versus local modes of processing visual stimuli in different species and individuals also can account for variation in illusion susceptibility (e.g., [38][39][40][41][42][43][44]). Differences in psychophysical discriminability capacities also are relevant, as are factors such as discrimination thresholds (acuity in size and numerosity discriminations), motivation to engage with tasks, previous testing histories that may conflict with or support a more illusory experience in newer tasks, and even factors such as how quickly or slowly individuals (and species) respond in tasks. It is likely that all of these factors and others play a role in the species differences and individual differences that are evident in the literature. In some cases, relevant factors could be controlled in ways that better isolate illusion susceptibility, although it is important to also assess illusory experiences in more naturalistic choice and decision setting (e.g., chimpanzees falling prey to the DBI when being allowed to look at and choose food items to immediately consume [45]).
Although researchers cannot (yet) adequately explain the individual differences seen in monkeys, or other animals, this is an attainable goal, and will allow a productive focus of future research. There is a richness in these individual differences for better understanding the cause(s) of illusory experiences, and more broadly for understanding the different phenomenal worlds of different species, different individuals within a species, and the same individuals tested at different times. Although there are certainly major differences in how some species may perceive and process sensory information relative to other species (e.g., the bat versus the reptile), there may also be substantial intraspecific differences that affect other behavioral and cognitive processes. As just one example, based on some of the studies shown in Table 1, differences in susceptibility to numerical or quantitative illusions could impact foraging behavior, social approach or avoidance behavior, and other natural behaviors that rely on perceiving and representing magnitude information such as quantity or number. The same is true for size-based judgments, which may be affected by those individuals who are more susceptible to illusory experiences.
Most likely, those individual differences do not lead to substantial fitness benefits to those who are less susceptible to illusions, or else there would have been selection against such susceptibility. However, this does not mean that illusory experiences are not detrimental. One could predict that illusory experiences may generate more decision errors in some kinds of choice tasks, or greater likelihood of errors in different kinds of memory tests, and especially those for which one must remember the actual attributes of a stimuli that could be misrepresented due to the illusory experience. As such, documenting and accommodating individual differences in illusory experience could aid in accounting for variance in animal cognition and behavior that has otherwise not been accounted for through the manipulation of other factors.

References

  1. 50 Optical Illusions That’ll Blow Your Mind. Available online: https://parade.com/1312776/marynliles/optical-illusions/ (accessed on 16 November 2022).
  2. Two Years Later, We Finally Know Why People Saw “The Dress” Differently. Available online: https://slate.com/technology/2017/04/heres-why-people-saw-the-dress-differently.html#:~:text=Remember%2C%20the%20dress%20is%20actually,Because%20shadows%20overrepresent%20blue%20light (accessed on 16 November 2022).
  3. Carbon, C.-C. Understanding human perception by human-made illusions. Front. Hum. Neurosci. 2014, 8, 566.
  4. Necker, L.A. Observations on some remarkable phenomena seen in Switzerland; And an optical phenomenon which occurs on viewing of a crystal or geometrical solid. Phil. Mag. 1832, 3, 329–337.
  5. Hering, E. Beitrage zur Physiologie; W. Engelmann: Leipzig, Germany, 1861.
  6. Zöllner, F. Ueber eine neue Art von Pseudoskopie und ihre Beziehungen zu den von Plateau und Oppel beschriebenen Bewegungsphänomenen. Ann. Phys. 1860, 186, 500–523.
  7. Gregory, R.L. Perceptual illusions and brain models. Proc. R. Soc. Lond. Ser. B Boil. Sci. 1968, 171, 279–296.
  8. Winslow, C.N. Visual illusions in the chick. Arch. Psychol. 1933, 153, 80.
  9. Dominguez, K.E. A Study of Visual Illusions in the Monkey. J. Genet. Psychol. 1954, 85, 105–127.
  10. Benhar, E.; Samuel, D. Visual illusions in the baboon (Papio anubis). Anim. Learn. Behav. 1982, 10, 115–118.
  11. Lõoke, M.; Marinelli, L.; Eatherington, C.J.; Agrillo, C.; Mongillo, P. Do Domestic Dogs (Canis lupus familiaris) Perceive Numerosity Illusions? Animals 2020, 10, 2304.
  12. Agrillo, C.; Santacà, M.; Pecunioso, A.; Petrazzini, M.E.M. Everything is subjective under water surface, too: Visual illusions in fish. Anim. Cogn. 2020, 23, 251–264.
  13. Cappellato, A.; Petrazzini, M.E.M.; Bisazza, A.; Dadda, M.; Agrillo, C. Susceptibility to Size Visual Illusions in a Non-Primate Mammal (Equus caballus). Animals 2020, 10, 1673.
  14. Petrazzini, M.E.M.; Bisazza, A.; Agrillo, C. Do domestic dogs (Canis lupus familiaris) perceive the Delboeuf illusion? Anim. Cogn. 2017, 20, 427–434.
  15. Byosiere, S.-E.; Feng, L.C.; Woodhead, J.K.; Rutter, N.J.; Chouinard, P.A.; Howell, T.J.; Bennett, P.C. Visual perception in domestic dogs: Susceptibility to the Ebbinghaus–Titchener and Delboeuf illusions. Anim. Cogn. 2017, 20, 435–448.
  16. Byosiere, S.; Chouinard, P.A.; Howell, T.J.; Bennett, P.C. Illusion susceptibility in domestic dogs. Ethology 2020, 126, 949–965.
  17. Santacà, M.; Petrazzini, M.E.M.; Agrillo, C.; Wilkinson, A. Can reptiles perceive visual illusions? Delboeuf illusion in red-footed tortoise (Chelonoidis carbonaria) and bearded dragon (Pogona vitticeps). J. Comp. Psychol. 2019, 133, 419–427.
  18. Fujita, K. Perception of the Ponzo illusion by rhesus monkeys, chimpanzees, and humans: Similarity and difference in the three primate species. Percept. Psychophys. 1997, 59, 284–292.
  19. Fagot, J.; Tomonaga, M. Effects of element separation on perceptual grouping by humans (Homo sapiens) and chimpanzees (Pan troglodytes): Perception of Kanizsa illusory figures. Anim. Cogn. 2001, 4, 171–177.
  20. Nakamura, N.; Watanabe, S.; Fujita, K. Pigeons perceive the Ebbinghaus-Titchener circles as an assimilation illusion. J. Exp. Psychol. Anim. Behav. Process. 2008, 34, 375–387.
  21. Fujita, K.; Blough, D.S.; Blough, P.M. Pigeons see the Ponzo illusion. Anim. Learn. Behav. 1991, 19, 283–293.
  22. Santaca, M.; Regaiolli, B.; Petrazzini, M.E.M.; Spiezio, C.; Agrillo, C. Preliminary study to investigate the Delboeuf illusion in ring-tailed lemurs (Lemur catta): Methodological Challenges. Anim. Behav. Cogn. 2017, 4, 365–377.
  23. Santacà, M.; Petrazzini, M.E.M.; Agrillo, C.; Wilkinson, A. Exploring the Müller-Lyer illusion in a nonavian reptile (Pogona vitticeps). J. Comp. Psychol. 2020, 134, 391–400.
  24. Agrillo, C.; Parrish, A.E.; Beran, M.J. Do primates see the solitaire illusion differently? A comparative assessment of humans (Homo sapiens), chimpanzees (Pan troglodytes), rhesus monkeys (Macaca mulatta), and capuchin monkeys (Cebus apella). J. Comp. Psychol. 2014, 128, 402–413.
  25. Agrillo, C.; Gori, S.; Beran, M.J. Do rhesus monkeys (Macaca mulatta) perceive illusory motion? Anim. Cogn. 2015, 18, 895–910.
  26. Parrish, A.E.; Brosnan, S.F.; Beran, M.J. 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. 2015, 41, 395–405.
  27. Parrish, A.E.; Beran, M.J. Children and monkeys overestimate the size of high-contrast stimuli. Atten. Percept. Psychophys. 2021, 83, 2123–2135.
  28. Delboeuf, J.L.R. Sur une nouvelle illusion d’optique . Acad. R. Sci. Lett. Beaux Arts Belg. Bull. 1892, 24, 545–558.
  29. Ebbinghaus, H. The Principles of Psychology: Vol. I. II; Viet: Leipzig, Germany, 1892.
  30. McGurk, E. Susceptibility to Visual Illusions. J. Psychol. 1865, 61, 127–143.
  31. Cretenoud, A.F.; Grzeczkowski, L.; Bertamini, M.; Herzog, M.H. Individual differences in the Müller-Lyer and Ponzo illusions are stable across different contexts. J. Vis. 2020, 20, 4.
  32. Cretenoud, A.F.; Grzeczkowski, L.; Kunchulia, M.; Herzog, M.H. Individual differences in the perception of visual illusions are stable across eyes, time, and measurement methods. J. Vis. 2021, 21, 26.
  33. Grzeczkowski, L.; Clarke, A.M.; Francis, G.; Mast, F.W.; Herzog, M.H. About individual differences in vision. Vis. Res. 2017, 141, 282–292.
  34. Coren, S.; Porac, C. Individual differences in visual-geometric illusions: Predictions from measures of spatial cognitive abilities. Percept. Psychophys. 1987, 41, 211–219.
  35. Santacà, M.; Agrillo, C.; Petrazzini, M.M. The Challenge of Illusory Perception of Animals: The Impact of Methodological Variability in Cross-Species Investigation. Animals 2021, 11, 1618.
  36. Parrish, A.E. Visual illusions: Insights from comparative cognition. In Comparative Cognition: Commonalities and Diversity; Anderson, J.R., Kuroshima, H., Eds.; Springer: Singapore, 2021; pp. 15–30.
  37. Parrish, A.E.; Agrillo, C. Current perspectives on primate perception. In Primate Cognitive Studies; Schwartz, B.L., Beran, M.J., Eds.; Cambridge University Press: Cambridge, UK, 2022; pp. 115–134.
  38. Berry, J.W. Müller-Lyer Susceptibility: Culture, Ecology or Race? Int. J. Psychol. 1971, 6, 193–197.
  39. Dakin, S.; Frith, U. Vagaries of Visual Perception in Autism. Neuron 2005, 48, 497–507.
  40. Fagot, J.; Deruelle, C. Processing of global and local visual information and hemispheric specialization in humans (Homo sapiens) and baboons (Papio papio). J. Exp. Psychol. Hum. Percept. Perform. 1997, 23, 429–442.
  41. Parron, C.; Fagot, J. Comparison of grouping abilities in humans (Homo sapiens) and baboons (Papio papio) with the Ebbinghaus illusion. J. Comp. Psychol. 2007, 121, 405–411.
  42. Hopkins, W.D.; Washburn, D.A. Matching visual stimuli on the basis of global and local features by chimpanzees (Pan troglodytes) and rhesus monkeys (Macaca mulatta). Anim. Cogn. 2002, 5, 27–31.
  43. De Lillo, C.; Palumbo, M.; Spinozzi, G.; Giustino, G. Effects of pattern redundancy and hierarchical grouping on global–local visual processing in monkeys (Cebus apella) and humans (Homo sapiens). Behav. Brain Res. 2012, 226, 445–455.
  44. Spinozzi, G.; De Lillo, C.; Salvi, V. Local advantage in the visual processing of hierarchical stimuli following manipulations of stimulus size and element numerosity in monkeys (Cebus apella). Behav. Brain Res. 2006, 166, 45–54.
  45. Parrish, A.E.; Beran, M. When less is more: Like humans, chimpanzees (Pan troglodytes) misperceive food amounts based on plate size. Anim. Cogn. 2014, 17, 427–434.
More
© Text is available under the terms and conditions of the Creative Commons Attribution (CC BY) license; additional terms may apply. By using this site, you agree to the Terms and Conditions and Privacy Policy.
Upload a video for this entry
Information
Subjects: Psychology
Contributors MDPI registered users' name will be linked to their SciProfiles pages. To register with us, please refer to https://encyclopedia.pub/register :
Michael J. Beran
,
Audrey E. Parrish
View Times: 365
Revisions: 3 times (View History)
Update Date: 14 Feb 2023
Table of Contents
    1000/1000
    Hot Most Recent
    Video Production Service
    Feedback