Illusory face detection in pure noise images: The role of interindividual variability in fMRI activation patterns

Abstract

Illusory face detection tasks can be used to study the neural correlates of top-down influences on face perception. In a typical functional magnetic resonance imaging (fMRI) study design, subjects are presented with pure noise images, but are told that half of the stimuli contain a face. The illusory face perception network is assessed by comparing blood oxygenation level dependent (BOLD) responses to images in which a face has been detected against BOLD activity related to images in which no face has been detected. In the present study, we highlight the existence of strong interindividual differences of BOLD activation patterns associated with illusory face perception. In the core system of face perception, 4 of 9 subjects had highly significant (p<0.05, corrected for multiple comparisons) activity in the bilateral occipital face area (OFA) and fusiform face area (FFA). In contrast, 5 of 9 subjects did not show any activity in these regions, even at statistical thresholds as liberal as p = 0.05, uncorrected. At the group level, this variability is reflected by non-significant activity in all regions of the core system. We argue that these differences might be related to individual differences in task execution: only some participants really detected faces in the noise images, while the other subjects simply responded in the desired way. This has several implications for future studies on illusory face detection. First, future studies should not only analyze results at the group level, but also for single subjects. Second, subjects should be explicitly queried after the fMRI experiment about whether they really detected faces or not. Third, if possible, not only the overt response of the subject, but also additional parameters that might indicate the perception of a noise stimulus as face should be collected (e.g., behavioral classification images).

Anomalous visual experience is linked to perceptual uncertainty and visual imagery vividness

“…Because pareidolia is a subjective experience influenced by top-down factors, we hypothesized that there should be individual variability in the frequency of these percepts. In line with this, we found that pareidolia experiences are reported with varying prevalence across studies that have used the same or similar experimental design (Liu et al, 2014 ; Rieth, Lee, Lui, Tian, & Huber, 2011 ; Zhang et al, 2008 ; Zimmermann, Stratil, Thome, Sommer, & Jansen, 2019 ). In Zhang et al ( 2008 ), the percentage of face-present responses in 16 subjects ranged from nearly 8% to more than 50% (standard deviation (SD) = 14%).…”

“…Previous studies of face pareidolia in noise have focused on the paradigm of Exp. 1a (Li et al, 2009(Li et al, , 2010Liu et al, 2014;Rieth et al, 2011;Zhang et al, 2008;Zimmermann et al, 2019), but our additional experiments demonstrate that this paradigm can be adapted to reveal the various factors that contribute to pareidolia proneness.…”

“…Rieth et al ( 2011 ) reported 39% face-present responses, after excluded nearly 25% of their 229 subjects who reported to see fewer than 5 faces in the whole experiment. At the cortical level, one recent study found that face-selective cortical areas were only activated in 4/9 subjects in this design (Zimmermann et al, 2019 ). These results clearly show a range of individual differences in pareidolia proneness that has not yet been explained.…”

Let’s face it: The lateralization of the face perception network as measured with fMRI is not clearly right dominant

“…High interindividual variability of the hemispheric lateralization of the face peerception network is also in accordance with our own anecdotal experience. Our research group has conducted numerous fMRI studies on face processing over the last years, often in the context of hemispheric lateralization (e.g., Frässle et al, 2016aFrässle et al, , 2016bFrässle et al, , 2016cHildesheim et al, 2020;Sahraei et al, 2021;Thome et al, 2021;Zimmermann et al, 2019). In these studies, it was often necessary to assess the fMRI activation patterns not only at the group level, but also at the individual level, e.g., in order to determine the spatial location of core system regions for further analyses.…”

Do you see the “face”? Individual differences in face pareidolia

“…It has been proposed that face pareidolia requires a match between external visual input and internal face templates. Using fMRI, researchers found that when an illusory face was detected from pure noise images, it was associated with blood-oxygen-level-dependent (BOLD) imaging activity in the face-selective areas, including bilateral OFA and FFA (Liu et al, 2014; Zhang et al, 2008; but see Zimmermann, Stratil, Thome, Sommer, & Jansen, 2019). Further whole brain analysis revealed a distributed network extending from the ventral occipitotemporal cortex to the prefrontal cortex and sublobar regions, indicating the activation of the internal face templates and top-down modulation on the external input.…”