Purchase this article with an account.
Marnix Naber, Tijn Knaap, Stefan Van der Stigchel; The extrapolation effect: an illusory experience of extended feature space beyond reality. Journal of Vision 2019;19(10):239. doi: https://doi.org/10.1167/19.10.239b.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
A target object that changes location across space appears ahead of a reference object in case the latter is shortly flashed at the same position. This perceptual mismatch is called the flash-lag effect and also occurs when targets change along feature dimensions other than spatial space, such as luminance. We show that a comparable extrapolation effect (EE) is observed when the reference is constantly visible instead of shortly flashed and when the target physically stops to change after it reaches full reference similarity. This novel design removes perceptual uncertainty, processing delays, and postdictive effects that may arise during the comparison of target and reference. The EE is most evident when a target stimulus differs strongly from its background on a feature such as luminance, and slowly increases in similarity towards the background reference as a function of time. At the moment the target stimulus stops changing and is physically similar to its background (e.g., equiluminant), the target appears to continue to change along the varied feature space. For example, the target appears brighter than its gray background after it changed from black to gray. The temporal dynamics of the EE are distinct from light adaptation. We also demonstrate that target contrast appears higher or lower after contrast increased or decreased towards a medium background contrast, respectively. Because the EE occurs with a predictable, fixed, endpoint reference rather than an unpredictable, temporary, flash reference, we conclude that the EE cannot be explained by attentional delays, perceptual latencies, postdiction, or temporal averaging. Instead our observations support the proposition that the visual system extrapolates changes in feature space. This is likely a general property of perception, either with the function to prepare for future events or as an epiphenomenal overshoot of changes in activity of neurons that are tuned to the moderated features.
This PDF is available to Subscribers Only