The BTPI: An online battery for measuring susceptibility to visual illusions

Abstract

Visual illusions provide a powerful tool for probing the mechanisms that underlie perception. While most previous studies of visual illusions focused on average group-level performance, less attention has been devoted to individual differences in susceptibility to illusions. Unlike in other perceptual domains, in which there are established, validated tools to measure individual differences, such tools are not yet available in the domain of visual illusions. Here, we describe the development and validation of the BTPI (Ben-Gurion University Test for Perceptual illusions), a new online battery designed to measure susceptibility to the influence of three prominent size illusions: The Ebbinghaus, the Ponzo, and the height-width illusions. The BTPI also measures perceptual resolution, reflected by the just noticeable difference (JND), to detect size differences in the context of each illusion. In Experiment 1 (N=143), we examined performance in typical self-paced tasks, whereas in Experiment 2 (N=69), we employed a fixed presentation duration paradigm. High test-retest reliability scores were found for all illusions, with little evidence for inter-correlations between different illusions. In addition, lower perceptual resolution (larger JND) was associated with a larger susceptibility to the illusory effect. The computerized task battery and analysis codes are freely available online.

Is there a neural common factor for visual illusions?

“…Taxonomizing illusions as spatial, temporal, and contrast illusions reflects this thinking. Recent research has clearly shown that strong correlations between different illusions are rare [6][7][8][9][10][11][12] (but see the recent work of Makowski and colleagues 21 ). In fact, Schwarzkopf and colleagues also reported that the illusion magnitudes in the Ebbinghaus and Ponzo illusions did not correlate significantly 3 .…”

“…Yet this has not been found to be the case across a multitude of studies. On the contrary, recent studies have shown that visual illusion magnitudes correlate only weakly with each other, even though test-retest reliability is usually good [6][7][8][9][10][11][12] . Notably, also in one of the aforementioned studies 3 , V1 surface area was found to correlate with Ebbinghaus and Ponzo illusion magnitudes but the magnitudes of the two illusions did not significantly correlate with each other (r = 0.24, p = 0.208).…”

Age-related changes in size perception: A tale of three illusions

“…The experimental session lasted approximately 20 minutes, and participants were compensated with 3.13 euros. In line with prior research (Mazuz et al, 2023), only participants exhibiting a goodness of fit (GOF) score exceeding 0.7 in all illusion tasks were included in the final analysis.…”

“…Although there are supportive findings for the hypothesis of increased reliance on priors with age, it is crucial to recognize that such a proposition may be overgeneralized and might not accurately describe the complexity of the aging brain. Existing literature has established an absence of a common factor for individual differences in vision, particularly regarding the mechanisms that underlie visual illusions (Coren et al, 1976;Cretenoud et al, 2019;Grzeczkowski et al, 2017;Mazuz et al, 2023). The recognition that different illusions are mediated by distinct perceptual mechanisms raises the possibility that aging may exert differential effects on these diverse mechanisms.…”

“…Our objective is to explore and identify potential variations in the impact of age on different functions and mechanisms, introducing a nuanced perspective that acknowledges the possibility of diverse patterns of influence. To explore this idea, we employed a standardized test of the susceptibility to visual illusions, recently developed in our lab, the Ben-Gurion University Test for Perceptual Illusions (BTPI; Mazuz et al, 2023). The BTPI is an online battery designed to measure individual differences in susceptibility to visual illusions.…”