A visual search advantage for illusory faces in objects

Abstract

Face detection is a priority of both the human and primate visual system. However, occasionally we misperceive faces in inanimate objects --"face pareidolia". A key feature of these 'false positives' is that face perception occurs in the absence of visual features typical of real faces. Human faces are known to be located faster than objects in visual search. Here we used a visual search paradigm to test whether illusory faces share this advantage. Search times were faster for illusory faces than for matched objects amongst both matched (Experiment 1) and diverse (Experiment 2) distractors, however search times for real human faces were faster and more efficient than objects with or without an illusory face. Importantly, this result indicates that illusory faces are processed quickly enough by the human brain to confer a visual search advantage, suggesting the engagement of a broadly-tuned mechanism that facilitates rapid face detection in cluttered environments.

A shared mechanism for facial expression in human faces and face pareidolia

“…Several lines of converging psychophysical and neuroimaging evidence suggest that face pareidolia and human faces share common mechanisms [21][22][23]. This is further supported by the finding that rhesus macaque monkeys also experience face pareidolia [19,20], suggesting that misperceiving faces in objects is a universal feature of the primate face detection system.…”

“…This is further supported by the finding that rhesus macaque monkeys also experience face pareidolia [ 19 , 20 ], suggesting that misperceiving faces in objects is a universal feature of the primate face detection system. However, although human and illusory faces both speed up visual search for a target [ 22 ], engage social attention via eye gaze direction [ 23 ] and share common neural mechanisms [ 21 ], there are important differences. Human faces are found even faster than illusory faces in visual search [ 22 ], and MEG has shown that the initial ‘face-like’ response to pareidolia only occurs for one-quarter of a second before their neural representation reorganizes to be more similar to objects than faces [ 21 ].…”

“…However, although human and illusory faces both speed up visual search for a target [ 22 ], engage social attention via eye gaze direction [ 23 ] and share common neural mechanisms [ 21 ], there are important differences. Human faces are found even faster than illusory faces in visual search [ 22 ], and MEG has shown that the initial ‘face-like’ response to pareidolia only occurs for one-quarter of a second before their neural representation reorganizes to be more similar to objects than faces [ 21 ]. Here, we also observed an asymmetry, as illusory faces had a larger influence on expression ratings for subsequent human faces than the reverse order ( figure 4 b ).…”

“…Face pareidolia is a spontaneous error of face detection which we share with other primates [ 19 , 20 ]. Human neuroimaging [ 21 ] and behavioural studies [ 22 , 23 ] have revealed that illusory faces share some mechanisms with human faces. However, there are notable differences in the neural representation of illusory and real faces, with the initial ‘face-like’ response to illusory faces resolving after only one-quarter of a second [ 21 ].…”

“…However, there are notable differences in the neural representation of illusory and real faces, with the initial ‘face-like’ response to illusory faces resolving after only one-quarter of a second [ 21 ]. One behavioural manifestation of this difference has been observed in visual search—although observers are faster to find a target object in search displays when it contains an illusory face, they are even faster to find a human face [ 22 ]. Understanding the processing of expression in errors of face detection (pareidolia) is important because examples of pareidolia are an intriguing case in which the facial ‘expression’ occurs in the absence of any underlying muscle movement or human facial features.…”