Cutaneous rabbit illusion

Last updated

The cutaneous rabbit illusion (also known as cutaneous saltation and sometimes the cutaneous rabbit effect or CRE) is a tactile illusion evoked by tapping two or more separate regions of the skin in rapid succession. The illusion is most readily evoked on regions of the body surface that have relatively poor spatial acuity, such as the forearm. A rapid sequence of taps delivered first near the wrist and then near the elbow creates the sensation of sequential taps hopping up the arm from the wrist towards the elbow, although no physical stimulus was applied between the two actual stimulus locations. Similarly, stimuli delivered first near the elbow then near the wrist evoke the illusory perception of taps hopping from elbow towards wrist. The illusion was discovered by Frank Geldard and Carl Sherrick of Princeton University, in the early 1970s, [1] and further characterized by Geldard (1982) [2] and in many subsequent studies. Geldard and Sherrick likened the perception to that of a rabbit hopping along the skin, giving the phenomenon its name. While the rabbit illusion has been most extensively studied in the tactile domain, analogous sensory saltation illusions have been observed in audition [3] [4] [5] and vision. [6] [7] [8] The word "saltation" refers to the leaping or jumping nature of the percept.

Contents

Experimental studies

From the moment of its discovery, the cutaneous rabbit illusion piqued the curiosity of researchers, and many experiments investigating the effect have been conducted, most of them on the forearm. Studies have consistently shown that the rabbit illusion occurs only when successive taps are closely spaced in time; the illusion disappears if the temporal separation between taps exceeds about 0.3 seconds (300 milliseconds). [2] A study showed that attention directed to one skin location reduces the perceptual migration of a tap placed at the attended location. [9] Another study showed that the illusory taps are associated with neural activity in the same area of the brain's sensory map that is activated by real taps to the skin. [10] Nevertheless, the specific neural mechanisms that underlie the rabbit illusion are unknown. Many interesting instantiations of the cutaneous rabbit illusion have been observed. The illusion is not just confined to the "body". [11] When subjects supported a stick across their index fingertips and received the taps via the stick, they reported sensing the illusory taps along the stick. This suggests that the cutaneous rabbit effect involves not only the intrinsic somatotopic representation but also the representation of the extended body schema that results from body-object interactions. Research has shown that the illusion can occur across non-contiguous body regions such as the fingers. [12] However, a subpopulation of participants apparently does not experience the effect on the fingertips. [13] The illusion has also been shown to occur both within and across the arms, suggesting that the illusion occurs after perceptual stages in the brain. [14] Visual cues—light flashes placed at particular locations along the arm—can influence the cutaneous rabbit illusion. [15] In addition, auditory and tactile stimuli can interact in the rabbit illusion. [16] In 2009, researchers of Philips Electronics demonstrated a jacket lined with actuator motors and designed to evoke various tactile sensations while watching a movie. The device takes advantage of the cutaneous rabbit illusion to reduce the number of actuators needed. [17] In keeping with the prediction of a Bayesian model, the perceptual attraction between the stimulus points is enhanced when the stimuli are made weaker. [18]

Explanation

Computational models have been put forward by several authors in an effort to explain the origins of the cutaneous rabbit illusion. [19] [20] [21] [22] [23] [24]

Perception underestimates the distance between successive taps to the skin. Stimuli are illustrated in the upper panels, along with their perception (forearm sketches). Corresponding human data and Bayesian model fits are plotted in the lower panels. For details, see Goldreich & Tong (2013). Bayesian model reproduction of length contraction illusions including the cutaneous rabbit illusion.jpg
Perception underestimates the distance between successive taps to the skin. Stimuli are illustrated in the upper panels, along with their perception (forearm sketches). Corresponding human data and Bayesian model fits are plotted in the lower panels. For details, see Goldreich & Tong (2013).

A Bayesian perceptual model [23] closely replicates the cutaneous rabbit and other tactile spatiotemporal illusions. According to this model, brain circuitry encodes the expectation, acquired through sensory experience, that tactile stimuli tend to be stationary or to move only slowly. The Bayesian model reaches an optimal probabilistic inference by combining uncertain spatial sensory information with a prior expectation for low-speed movement (a Gaussian prior distribution over velocity, with mean 0). The expectation that stimuli tend to move slowly results in the perceptual conclusion that rapidly successive stimuli are more likely to be closer together on the skin.

The Bayesian model was further developed [24] and shown to replicate the perception of humans to both simple (e.g., two-tap) and more complex (multi-tap) stimulus sequences, such as the 3-tap tau effect and the 15-tap rabbit illusion. The Bayesian model replicates the effects of selective spatial attention on the rabbit illusion percept [9] and is compatible with both the out-of-body rabbit illusion [11] and crossmodal influences on the rabbit illusion. [15] Perceptual prediction and postdiction are emergent properties of the Bayesian model. A freeware computer program, Leaping Lagomorphs, implements the Bayesian model.

For the case of two taps to the skin, the Bayesian model perceives the length between taps, l*, to be a function of the actual length, l, and the elapsed time, t:

l* = l/1 + 2(τ/t)2

This is the perceptual length contraction formula, [24] [18] so-named [23] in analogy with the physical length contraction described in the theory of relativity. Note that, just as observed in rabbit illusion experiments, the formula shows that l* underestimates l to a greater extent when t is made smaller; as t becomes large, l* approaches l and the illusion disappears. [9] The model's parameter, tau (τ), is a time constant for tactile space perception; the value of tau determines how rapidly the perceived length approaches the actual length as the time between stimuli, t, is increased. The perceived length equals one-third the actual length when t = τ, and two-thirds the actual length when t = 2τ.

Goldreich and Tong (2013) showed that tau is the ratio of the observer's low-speed expectation and tactile spatial acuity; they estimated the value of tau to be approximately 0.1 s on the forearm. [24] A novel prediction of the Bayesian model, pointed out by Goldreich and Tong (2013), is that the amount of length contraction experienced will depend on the intensity of a tactile stimulus: lighter taps, which are more difficult to localize, should produce larger tau values and therefore more length contraction. Tong et al. (2016) confirmed this prediction experimentally. [18]

An illusion that appears to be closely related to the rabbit illusion is the tau effect. The tau effect arises when an observer judges the distance between consecutive stimuli in a sequence. If the distance from one stimulus to the next is constant, but the time elapsed from one stimulus to the next is not constant, then subjects tend to perceive the interval that is shorter in time as also being shorter in distance. [25] Thus, like the rabbit illusion, the tau effect reveals that stimulus timing affects the perception of stimulus spacing. Goldreich (2007) [23] proposed that the cutaneous rabbit illusion and the tau effect both result from the same low-speed prior expectation. Indeed, the same Bayesian model—characterized by the perceptual length contraction formula above—replicates both effects. [24] Another illusion that is plausibly related to the cutaneous rabbit and the tau effect is the kappa effect. The kappa effect (or perceptual time dilation [23] ) is in essence the converse of the tau effect: the longer of two spatial intervals between stimuli is perceived to be longer in time. Goldreich (2007) [23] showed that, under conditions of temporal as well as spatial uncertainty, the Bayesian model produces the kappa effect. The perceptual length contraction formula in that case still applies, but the "t" in the formula refers to perceived rather than actual time.

Related Research Articles

<span class="mw-page-title-main">Perception</span> Interpretation of sensory information

Perception is the organization, identification, and interpretation of sensory information in order to represent and understand the presented information or environment. All perception involves signals that go through the nervous system, which in turn result from physical or chemical stimulation of the sensory system. Vision involves light striking the retina of the eye; smell is mediated by odor molecules; and hearing involves pressure waves.

An illusion is a distortion of the senses, which can reveal how the mind normally organizes and interprets sensory stimulation. Although illusions distort the human perception of reality, they are generally shared by most people.

A tactile illusion is an illusion that affects the sense of touch. Some tactile illusions require active touch, whereas others can be evoked passively. In recent years, a growing interest among perceptual researchers has led to the discovery of new tactile illusions and to the celebration of tactile illusions in the popular science press. Some tactile illusions are analogous to visual and auditory illusions, suggesting that these sensory systems may process information in similar ways; other tactile illusions don't have obvious visual or auditory analogs.

Stimulus modality, also called sensory modality, is one aspect of a stimulus or what is perceived after a stimulus. For example, the temperature modality is registered after heat or cold stimulate a receptor. Some sensory modalities include: light, sound, temperature, taste, pressure, and smell. The type and location of the sensory receptor activated by the stimulus plays the primary role in coding the sensation. All sensory modalities work together to heighten stimuli sensation when necessary.

Postdiction involves explanation after the fact. In skepticism, it is considered an effect of hindsight bias that explains claimed predictions of significant events such as plane crashes and natural disasters. In religious contexts, theologians frequently refer to postdiction using the Latin term vaticinium ex eventu. Through this term, skeptics postulate that many biblical prophecies appearing to have come true may have been written after the events supposedly predicted, or that the text or interpretation may have been modified after the event to fit the facts as they occurred.

Retrodiction is the act of making a prediction about the past. It is also known as postdiction.

Multisensory integration, also known as multimodal integration, is the study of how information from the different sensory modalities may be integrated by the nervous system. A coherent representation of objects combining modalities enables animals to have meaningful perceptual experiences. Indeed, multisensory integration is central to adaptive behavior because it allows animals to perceive a world of coherent perceptual entities. Multisensory integration also deals with how different sensory modalities interact with one another and alter each other's processing.

Sensory substitution is a change of the characteristics of one sensory modality into stimuli of another sensory modality.

The kappa effect or perceptual time dilation is a temporal perceptual illusion that can arise when observers judge the elapsed time between sensory stimuli applied sequentially at different locations. In perceiving a sequence of consecutive stimuli, subjects tend to overestimate the elapsed time between two successive stimuli when the distance between the stimuli is sufficiently large, and to underestimate the elapsed time when the distance is sufficiently small.

The tau effect is a spatial perceptual illusion that arises when observers judge the distance between consecutive stimuli in a stimulus sequence. When the distance from one stimulus to the next is constant, and the time elapsed from one stimulus to the next is also constant, subjects tend to judge the distances, correctly, as equal. However, if the distance from one stimulus to the next is constant, but the time elapsed from one stimulus to the next is not constant, then subjects tend to misperceive the interval that has the shorter temporal interval as also having a shorter spatial interval. Thus, the tau effect reveals that stimulus timing affects the perception of stimulus spacing. Time is also a perceived quantity and subject to its own illusions; research indicates that in the tau effect, perceived stimulus spacing follows perceived (phenomenal) time rather than actual (physical) time.

A sensory cue is a statistic or signal that can be extracted from the sensory input by a perceiver, that indicates the state of some property of the world that the perceiver is interested in perceiving.

<span class="mw-page-title-main">Flash lag illusion</span> Optical illusion

The flash lag illusion or flash-lag effect is a visual illusion wherein a flash and a moving object that appear in the same location are perceived to be displaced from one another. Several explanations for this simple illusion have been explored in the neuroscience literature.

The study of time perception or chronoception is a field within psychology, cognitive linguistics and neuroscience that refers to the subjective experience, or sense, of time, which is measured by someone's own perception of the duration of the indefinite and unfolding of events. The perceived time interval between two successive events is referred to as perceived duration. Though directly experiencing or understanding another person's perception of time is not possible, perception can be objectively studied and inferred through a number of scientific experiments. Some temporal illusions help to expose the underlying neural mechanisms of time perception.

<span class="mw-page-title-main">Chubb illusion</span> Optical illusion

The Chubb illusion is an optical illusion or error in visual perception in which the apparent contrast of an object varies substantially to most viewers depending on its relative contrast to the field on which it is displayed. These visual illusions are of particular interest to researchers because they may provide valuable insights in regard to the workings of human visual systems.

<span class="mw-page-title-main">Two-point discrimination</span> Ability to discern between single and pairs of points on ones skin

Two-point discrimination (2PD) is the ability to discern that two nearby objects touching the skin are truly two distinct points, not one. It is often tested with two sharp points during a neurological examination and is assumed to reflect how finely innervated an area of skin is.

Bayesian approaches to brain function investigate the capacity of the nervous system to operate in situations of uncertainty in a fashion that is close to the optimal prescribed by Bayesian statistics. This term is used in behavioural sciences and neuroscience and studies associated with this term often strive to explain the brain's cognitive abilities based on statistical principles. It is frequently assumed that the nervous system maintains internal probabilistic models that are updated by neural processing of sensory information using methods approximating those of Bayesian probability.

<span class="mw-page-title-main">Somatosensory system</span> Nerve system for sensing touch, temperature, body position, and pain

In physiology, the somatosensory system is the network of neural structures in the brain and body that produce the perception of touch, as well as temperature (thermoception), body position (proprioception), and pain. It is a subset of the sensory nervous system, which also represents visual, auditory, olfactory, and gustatory stimuli.

<span class="mw-page-title-main">Perceptual learning</span>

Perceptual learning is learning better perception skills such as differentiating two musical tones from one another or categorizations of spatial and temporal patterns relevant to real-world expertise. Examples of this may include reading, seeing relations among chess pieces, and knowing whether or not an X-ray image shows a tumor.

Chronostasis is a type of temporal illusion in which the first impression following the introduction of a new event or task-demand to the brain can appear to be extended in time. For example, chronostasis temporarily occurs when fixating on a target stimulus, immediately following a saccade. This elicits an overestimation in the temporal duration for which that target stimulus was perceived. This effect can extend apparent durations by up to half a second and is consistent with the idea that the visual system models events prior to perception.

Haptic memory is the form of sensory memory specific to touch stimuli. Haptic memory is used regularly when assessing the necessary forces for gripping and interacting with familiar objects. It may also influence one's interactions with novel objects of an apparently similar size and density. Similar to visual iconic memory, traces of haptically acquired information are short lived and prone to decay after approximately two seconds. Haptic memory is best for stimuli applied to areas of the skin that are more sensitive to touch. Haptics involves at least two subsystems; cutaneous, or everything skin related, and kinesthetic, or joint angle and the relative location of body. Haptics generally involves active, manual examination and is quite capable of processing physical traits of objects and surfaces.

References

  1. ↑ Geldard, F. A.; Sherrick, C. E. (13 October 1972). "The Cutaneous "Rabbit": A Perceptual Illusion". Science. 178 (4057): 178–179. Bibcode:1972Sci...178..178G. doi:10.1126/science.178.4057.178. PMID   5076909. S2CID   41846475.
  2. 1 2 Geldard, FA (July 1982). "Saltation in somesthesis". Psychological Bulletin. 92 (1): 136–75. doi:10.1037/0033-2909.92.1.136. PMID   7134325.
  3. ↑ Bremer, CD; Pittenger, JB; Warren, R; Jenkins, JJ (December 1977). "An illusion of auditory saltation similar to the cutaneous "rabbit"". The American Journal of Psychology. 90 (4): 645–54. doi:10.2307/1421738. JSTOR   1421738. PMID   610449.
  4. ↑ Shore, DI; Hall, SE; Klein, RM (June 1998). "Auditory saltation: a new measure for an old illusion". The Journal of the Acoustical Society of America. 103 (6): 3730–3. Bibcode:1998ASAJ..103.3730S. doi:10.1121/1.423093. PMID   9637053.
  5. ↑ Getzmann, S (February 2009). "Exploring auditory saltation using the "reduced-rabbit" paradigm". Journal of Experimental Psychology: Human Perception and Performance. 35 (1): 289–304. doi:10.1037/a0013026. PMID   19170489.
  6. ↑ Geldard, FA (June 1976). "The saltatory effect in vision". Sensory Processes. 1 (1): 77–86. PMID   1029079.
  7. ↑ Lockhead, GR; Johnson, RC; Gold, FM (June 1980). "Saltation through the blind spot". Perception and Psychophysics. 27 (6): 545–9. doi: 10.3758/bf03198683 . PMID   7393702.
  8. ↑ Khuu, SK; Kidd, JC; Badcock, DR (Aug 15, 2011). "The influence of spatial orientation on the perceived path of visual saltatory motion". Journal of Vision. 11 (9): 5. doi: 10.1167/11.9.5 . PMID   21844167.
  9. 1 2 3 Kilgard, MP; Merzenich, MM (23 February 1995). "Anticipated stimuli across skin". Nature. 373 (6516): 663. Bibcode:1995Natur.373..663K. doi: 10.1038/373663a0 . PMID   7854442.
  10. ↑ Blankenburg, Felix; Ruff, Christian C.; Deichmann, Ralf; Rees, Geraint; Driver, Jon (1 January 2006). "The Cutaneous Rabbit Illusion Affects Human Primary Sensory Cortex Somatotopically". PLOS Biology. 4 (3): e69. doi:10.1371/journal.pbio.0040069. PMC   1382015 . PMID   16494530. Open Access logo PLoS transparent.svg
  11. 1 2 Miyazaki, M; Hirashima, M; Nozaki, D (Feb 3, 2010). "The "cutaneous rabbit" hopping out of the body" (PDF). Journal of Neuroscience. 30 (5): 1856–60. doi: 10.1523/JNEUROSCI.3887-09.2010 . PMC   6633980 . PMID   20130194.
  12. ↑ Warren, JP; Santello, M; Helms Tillery, SI (October 2010). "Electrotactile stimuli delivered across fingertips inducing the Cutaneous Rabbit Effect". Experimental Brain Research. 206 (4): 419–26. doi:10.1007/s00221-010-2422-0. PMID   20862459. S2CID   8762049.
  13. ↑ Warren, JP; Tillery, SI (Nov 7, 2011). "Tactile perception: do distinct subpopulations explain differences in mislocalization rates of stimuli across fingertips?". Neuroscience Letters. 505 (1): 1–5. doi:10.1016/j.neulet.2011.04.057. PMID   21575679. S2CID   8631372.
  14. ↑ Eimer, M., B. Foster, and J. Vibell. "Cutaneous Saltation within and across Arms: A New Measure of the Saltation Illusion in Somatosensation." Percept Psychophys 67.3 (2005) 458-68. Web.
  15. 1 2 Asai, T; Kanayama, N (22 October 2012). "'Cutaneous Rabbit' Hops toward a Light: Unimodal and Cross-modal Causality on the Skin". Frontiers in Psychology. 3: 427. doi: 10.3389/fpsyg.2012.00427 . PMC   3490328 . PMID   23133432.
  16. ↑ Trojan, J; Getzmann, S; Möller, J; Kleinböhl, D; Hölzl, R (2009). "Tactile-auditory saltation: Spatiotemporal integration across sensory modalities". Neuroscience Letters. 460 (2): 156–160. doi:10.1016/j.neulet.2009.05.053. PMID   19477228. S2CID   6790348.
  17. ↑ Jones, Willie D. (18 March 2009). "Jacket Lets You Feel the Movies". EEE Spectrum Online.
  18. 1 2 3 Tong, Jonathan; Ngo, Vy; Goldreich, Daniel (1 August 2016). "Tactile length contraction as Bayesian inference". Journal of Neurophysiology. 116 (2): 369–379. doi:10.1152/jn.00029.2016. PMC   4969385 . PMID   27121574.
  19. ↑ Brigner, WL (April 1988). "Saltation as a rotation of space-time axes". Percept mot Skills. 66 (2): 637–8. doi:10.2466/pms.1988.66.2.637. PMID   3399342. S2CID   40644821.
  20. ↑ Wiemer, J; Spengler, F; Joublin, F; Stagge, P; Wacquant, S (February 2000). "Learning cortical topography from spatiotemporal stimuli". Biological Cybernetics. 82 (2): 173–87. doi:10.1007/s004220050017. PMID   10664104. S2CID   8411380.
  21. ↑ Grush, R (September 2005). "Internal models and the construction of time: generalizing from state estimation to trajectory estimation to address temporal features of perception, including temporal illusions". Journal of Neural Engineering. 2 (3): S209–18. Bibcode:2005JNEng...2S.209G. doi:10.1088/1741-2560/2/3/S05. PMID   16135885. S2CID   15077933.
  22. ↑ Flach, R; Haggard, P (June 2006). "The cutaneous rabbit revisited". Journal of Experimental Psychology: Human Perception and Performance. 32 (3): 717–32. doi:10.1037/0096-1523.32.3.717. PMID   16822134.
  23. 1 2 3 4 5 6 Goldreich, D (Mar 28, 2007). "A Bayesian perceptual model replicates the cutaneous rabbit and other tactile spatiotemporal illusions". PLOS ONE. 2 (3): e333. Bibcode:2007PLoSO...2..333G. doi: 10.1371/journal.pone.0000333 . PMC   1828626 . PMID   17389923. Open Access logo PLoS transparent.svg
  24. 1 2 3 4 5 6 Goldreich, D; Tong, J (10 May 2013). "Prediction, Postdiction, and Perceptual Length Contraction: A Bayesian Low-Speed Prior Captures the Cutaneous Rabbit and Related Illusions". Frontiers in Psychology. 4: 221. doi: 10.3389/fpsyg.2013.00221 . PMC   3650428 . PMID   23675360.
  25. ↑ Helson, H; King, S.M. (1931). "The tau effect: an example of psychological relativity". J Exp Psychol. 14 (3): 202–217. doi:10.1037/h0071164.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.