Release from inhibition reveals the visual past

Processing visual ambiguity in fractal patterns: Pareidolia as a sign of creativity

Creativity is a highly valued and beneficial skill that empirical research typically probes using “divergent thinking” (DT) tasks such as problem solving and novel idea generation. Here, in contrast, we examine the perceptual aspect of creativity by asking whether creative individuals are more likely to perceive recognizable forms in ambiguous stimuli –a phenomenon known as pareidolia. To this end, we designed a visual task in which participants were asked to identify as many recognizable forms as possible in cloud-like fractal images. We found that pareidolic perceptions arise more often and more rapidly in highly creative individuals. Furthermore, high-creatives report pareidolia across a broader range of image contrasts and fractal dimensions than do low creatives. These results extend the established body of work on DT by introducing divergent perception as a complementary manifestation of the creative mind, thus clarifying the perception-creation link while opening new paths for studying creative behavior in humans.

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Creativity has been linked to divergent thinking

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Creativity is associated with enhanced pareidolia (i.e., divergent perception)

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High-creatives report pareidolia across a broader range of image fractal dimensions

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Divergent perception constitutes a promising phenomenon for the study of creativity

A Model for a Filling-in Process Triggered by Edges Predicts "Conflicting" Afterimage Effects

The goal of our research was to develop a compound computational model that predicts the "opposite" effects of the alternating aftereffects stimuli, such as the "color dove illusion" (Barkan and Spitzer, 2017), and the "filling in the afterimage after the image" (van Lier et al., 2009). The model is based on a filling-in mechanism, through a diffusion equation where the color and intensity of the perceived surface are obtained through a diffusion process of color from the stimulus edges. The model solves the diffusion equation with boundary conditions that takes the locations of the chromatic edges of the chromatic inducer (chromatic stimulus) and the achromatic remaining contours into account. These contours (edges) trigger the diffusion process. The same calculations are done for both types of afterimage effects, with the only difference related to the location of the remaining contour. While a gradient toward the inducing color produces a perception of the complementary color, an opposite gradient yields the perception of the same color as that of the chromatic inducer. Furthermore, we show that the same computational model can also predict new alternating aftereffects stimuli, such as the spiral stimulus, and the averaging of colors in alternating afterimage stimuli described by Anstis et al. (2012). The suggested model is able to predict most of the additional properties related to the "conflicting" phenomena that have been recently described in the literature, and thus supports the idea that a shared visual mechanism is responsible for both the positive and the negative effects.

Simulations of induced visual scene fading with boundary offset and filling-in

Blurred images can appear to fade to uniform brightness and color when viewed with some types of visual transient stimuli. Simons et al. (2006) identified the conditions where such scene fading occurs and noted that their findings were inconsistent with mechanisms that have been used to explain other fading effects. We show that their empirical findings are consistent with a neural model of visual perception that hypothesizes filling-in of brightness and color that is constrained by signals from a boundary contour system. Certain types of transients can weaken the boundary responses and thereby induce scene fading. The simulations explain how even small transient changes can produce scene fading effects across large parts of an image.

Quantification of artistic style through sparse coding analysis in the drawings of Pieter Bruegel the Elder

Recently, statistical techniques have been used to assist art historians in the analysis of works of art. We present a novel technique for the quantification of artistic style that utilizes a sparse coding model. Originally developed in vision research, sparse coding models can be trained to represent any image space by maximizing the kurtosis of a representation of an arbitrarily selected image from that space. We apply such an analysis to successfully distinguish a set of authentic drawings by Pieter Bruegel the Elder from another set of well-known Bruegel imitations. We show that our approach, which involves a direct comparison based on a single relevant statistic, offers a natural and potentially more germane alternative to wavelet-based classification techniques that rely on more complicated statistical frameworks. Specifically, we show that our model provides a method capable of discriminating between authentic and imitation Bruegel drawings that numerically outperforms well-known existing approaches. Finally, we discuss the applications and constraints of our technique.

Orientation tuning of a two-stimulus afterimage: Implications for theories of filling-in

Sequential viewing of 2 orthogonally related gratings produces an afterimage related to the firstgrating (Vidyasagar, Buzas, Kisyarday, & Eysel, 1999; Francis & Rothmayer, 2003). We investigated how the appearance of the afterimage depended on the relative orientations of the 2 stimulus gratings. We firstanalyzethetheoretical explanation of the appearance of the afterimage that was proposed by Francis and Rothameyer (2003). From the analysis, we show that the model must predict a rapid drop in afterimage occurrence as the gratings deviate from orthogonal. We also show that the model predicts that the shape of the afterimage should always be orthogonal to the second grating. We then report on 2 experiments that test the properties of the model and find that the experimental data are strikingly different from the model predictions. From these discrepancies we identify the key deficits of the current version of the model.

Attentional effects on afterimages: Theory and data

We explore attentional effects on afterimages in the framework of the FACADE model of visual perception. We first show that the FACADE model can account for the experimental findings of Suzuki and Grabowecky [Suzuki, S., & Grabowecky, M. (2003). Attention during adaptation weakens negative afterimages. Journal of Experimental Psychology: Human Perception and Performance 29, 793-807] that afterimages are weaker when the inducing stimulus is attended. We then analyze the model's behavior with attentional influences on a two-stimulus afterimage studied by Francis and Rothmayer [Francis, G., & Rothmayer, M. (2003). Interactions of afterimages for orientation and color: Experimental data and model simulations. Perception & Psychophysics 65, 508-522]. The model predicts that attentional focus directed towards the first stimulus has little effect on afterimage strength. In contrast, the model predicts that attentional focus on the second stimulus should increase the strength of the afterimage compared to when attention is focused elsewhere. Moreover, the model predicts that the attentional effects on the second stimulus should vary with time after offset of the second inducing stimulus. All of the model predictions are validated in an experiment. The model and experimental results extend and clarify previous explanations of attentional effects and afterimages.

The time course of visual afterimages: data and theory

Sequential viewing of two orthogonally related patterns produces an afterimage of the first pattern (Vidyasagar et al, 1999 Nature 399 422-423; Francis and Rothmayer, 2003 Perception and Psychophysics 65 508-522). We investigated how the timing between the first stimulus (a vertical bar grating) and the second stimulus (a horizontal bar grating) affected the visibility of the afterimage (a perceived vertical grating). As the duration from offset of the first stimulus increased, reports of afterimages decreased. Holding fixed the total time from offset of the first stimulus and increasing the duration from offset of the second stimulus while decreasing the time between the first and second stimuli, caused a decrease in afterimage reports. We interpret this finding in terms of Grossberg's BCS - FCS (boundary contour system--feature contour system) theory. In this theory, the afterimage percept is the result of color complement after-responses in the FCS system interacting with orientation after-responses in the BCS system. The two types of after-responses interact at a stage of neural filling-in to produce the afterimage percept. As the duration between the stimuli increases, the color after-responses weaken so that visible filling-in is less likely to occur. A similar effect occurs for the orientation after-responses but at a faster time scale. Simulations of the model match the experimental data.

Using afterimages for orientation and color to explore mechanisms of visual filling-in

Simulations of Grossberg's FACADE model of visual perception have previously been used to explain afterimage percepts produced by viewing a sequence of orthogonally oriented gratings. Additional simulations of the model are now used to predict new afterimage percepts. One simulation emphasizes that the afterimage percepts are the result of orientation afterresponses and color afterresponses that interact at a filling-in stage. We report experimental data that agree with FACADE's prediction. A second simulation emphasizes the properties of the model's filling-in stage and predicts a situation where the afterimage percept should not appear. We report experimental data indicating that this model prediction is incorrect. We argue that the model is unable to account for this result unless the filling-in stage mechanisms are different from a diffusive-type process. We propose an alternative mechanism, and simulations demonstrate the system's ability to account for the afterimage data.

Using afterimages to test neural mechanisms for perceptual filling-in

Many theories of visual perception propose that brightness information spreads from edges to define the perceived intensity of the interior of visual surfaces. Several theories of visual perception have hypothesized that this filling-in process is similar to a diffusion of information where the signals coding brightness spread to nearest neighbors. This paper shows that diffusive mechanisms fail to account for the characteristics of certain afterimage percepts that seem to be dependent on the filling-in process. A psychophysical experiment tests a key property of diffusion-based filling-in mechanisms and finds data that rejects this class of models. A non-diffusive based filling-in mechanism is proposed and is shown to act much like the diffusive based mechanism in many instances, but also produces afterimage percepts that match the experimental data.

Interactions of afterimages for orientation and color: experimental data and model simulations

Sequential viewing of two orthogonally related patterns produces an afterimage of the first pattern. We report an experiment that quantifies some properties of this type of afterimage. It is shown that it is important for the two patterns to have orthogonal orientations and that the appearance of the afterimage does not depend on the spatial frequency of the second pattern. We then show that Grossberg's model of interacting boundary and feature contour systems can account for the observed properties of these afterimages.

Electrophysiological correlates of the visual after effect by means of visual evoked potentials

An attempt was made to determine whether changes of electrical activity could be seen in the posterior cortex during an after image of high frequency luminance gratings. Steady state visual evoked potentials were recorded (midoccipital, right and left temporo-occipital sites) immediately after a period of visual adaptation (15 min) to the stimulus, while the subjects experienced the after image. During this illusion, frequencies of the fast Fourier transform spectra linked to the stimulation differed from the noise and were larger at temporo-occipital sites than at the midoccipital one. In view of these results, the hypothesis that the after effect represents a short term storage of the temporal characteristics of the stimulus is evoked.