Kappa effect
The Kappa Effect is a psychological phenomenon related to the perception of distance, time and speed. It is a temporal illusion that, in some cases, can alter one’s judgement of time. The Kappa effect arises when observers judge the amount of elapsed time between two stimuli in a sequence of consecutive stimuli. Stimuli can be visual, like flashes of light; auditory, like auditory tones; or tactile, like stimulation of the skin. When a subject is required to make judgments about ambiguous temporal intervals (the length of elapsed time) between each of these stimuli, they often base their decision on the familiar functional relations between spatial separation, time, and average velocity. These estimations of the length of time between stimuli can be influenced by the spatial separation, or the distance, between each of the stimuli. The elapsed time between two stimuli can be made to appear shorter (or longer) by decreasing (or increasing) the distance between the two stimuli[1] Therefore, even when the the length of elapsed time between stimuli in a sequence is kept the same throughout the sequence, we tend to over-estimate the amount of time between each stimuli when the distance between them is longer. Equally, we tend to under-estimate the amount of elapsed time between each stimuli in a sequence when the distance between them is shorter.
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[edit] Temporal Judgments and the Spatial Context
An individual tends to experience the Kappa effect when observing a sequence of stimuli in which the temporal separation (duration) between each stimuli is constant, but the spatial separation (distance) between each of the stimuli varies. As a result, the observer tends to base their judgments of the temporal separation between each stimuli on the spatial separation between each of these stimuli. Correspondingly, the Kappa effect is a temporal illusion that causes the observer to increase/decrease their judgments of temporal separation between stimuli as the spatial separation between these stimuli increases/decreases, even though the temporal separation between the stimuli stays constant[1]. Studies often observe the kappa effect by using visual modality. For example, let's say three light sources, X, Y, and Z, are flashed successively in the dark with equal time intervals between each of the flashes. If the light sources are placed at different positions, with X and Y closer together than Y and Z, the kappa effect is created. This is because the time interval between the X and Y lights is perceived to be shorter than that between the Y and Z since the distance between X and Y is shorter[2] In contrast, the tau effect occurs when the spatial separation between stimuli is constant and the temporal separation is varied, resulting in the observer increasing/decreasing their judgment of spatial separation as temporal separation increases/decreases. For example, when the same light sources X, Y, and Z are flashed successively in the dark with a shorter time interval between X and Y than between Y and Z, the tau effect is created that X and Y are closer together in space than is Y and Z.[2].
[edit] Constant Velocity
The constant velocity hypothesis, a theory proposed by Jones and Huang (1982), attempts to account for this temporal illusion.When stimuli are displayed successively, our brain incorporates a prior expectation of speed when judging spatiotemporal intervals. This assumption of velocity can influence our perception of the distance between stimuli. For the judgment of spatial intervals, the visual system and our brain work together to incorporate knowledge of the average duration of the temporal intervals between stimuli and apply it to expected temporal intervals that would be required to traverse the given distance between two stimuli at constant velocity[1]. The constant velocity hypothesis suggests that when individuals observe successive stimuli, they expect the temporal separation between each stimuli to reflect uniform motion[3] Consequently, the observer assumes that a given distance in spatial separation between stimuli requires a certain amount of temporal separation that is based on uniform motion. Therefore, this assumption of motion is applied to sequences of things as they unfold. As a result, the kappa effect occurs when all of our knowledge about motion gets applied to these sequences, which sometimes causes us to make mistakes[4]
[edit] Uniform motion
Uniform motion plays a role in our judgments of temporal separation between stimuli.[5] Participants observed eight white dots that successively appeared in one direction in a horizontal alignment along a straight line. When the temporal separation was constant and the spatial separation between the dots varied, they observed the kappa effect, which follows the constant velocity hypothesis. However, when both the temporal and spatial separation between the dots varied, they failed to observe the response pattern that the constant velocity hypothesis predicts. A possible explanation may be that it is difficult to perceive a uniform motion from such varying, complicated patterns. The results of this study suggest that the context of observed events may affect our temporal perception.
[edit] Motion in Different Contexts
The kappa effect appears to depend strongly on phenomenal rather than physical extent[1]. Kappa effect gets bigger as things go faster.[3]demonstrates the tendency of the observer to apply their previous knowledge of motion to a sequence of stimuli. In this study, subjects observed vertically arranged stimuli. The Kappa effect was stronger for sequences moving downward. This can be attributed to the expectation of downward acceleration and upward deceleration, in that the perceived accelerated downward motion causes us to underestimate temporal separation judgments.
[edit] Auditory Stimuli
The Kappa Effect also can be demonstrated by auditory stimuli to discuss the perceptual relation between space and time. “Increasing the distance between sound sources marking time intervals leads to a decrease of the perceived duration.”[6]The kappa effect has been observed for auditory stimuli that move in SPACE (think loudspeakers at different places in the room) in addition to frequency.[6]
[edit] References
- ^ a b c d Jones, B. & Huang, Y. L. (1982). Space-time dependencies in psychopyhsical judgment of extent and duration: algebraic models of the tau and kappa effects. 'Psychological Bulletin,91(1), 128-142.
- ^ a b TAU- AND KAPPA-EFFECTS. Elsevier's Dictionary of Psychological Theories. Oxford: Elsevier Science & Technology, 2006. Credo Reference. 29 May 2008
- ^ a b Masuda, T., Kimura, A., Dan, I. & Wada, Y. (2011). Effects of environmental context on temporal perception bias in apparent motion. Vision Research, 51, 1728-1740.
- ^ Dr. Molly J. Henry, Max Planck Institute for Human Cognitive and Brain Sciences; Leipzig, Germany
- ^ Sarrusazin, J. C., Giraudo, M. D., Pailhous, J., & Bootsma, R. (2004). Dynamics of balancing space and time in memory: tau and kappa effects revisited . Journal of Experimental Psychology: Human Perception and Performance, 30(3), 411-430,
- ^ a b Roy, M., Kuroda, T., & Grondin, S. (2011). Effect of space on auditory temporal processing with a single-stimulus method. Advances in Sound Localization, 95-104
