“An old-time hominid would be liable to pay dearly, had s/he failed to recognize a pair of glowing dots in the bush at dark as the eyes of a predator, mistaking it for two fireflies” David Navon
We tend to see faces in objects that have constituent parts resembling those of a face. This is an example of a phenomenon called pareidolia, which involves the perception of an ambiguous and random stimulus as significant, such as seeing faces in landscapes, clouds - or even in grilled toasts [1
]. Why and how do we tend to see faces in objects that have constituent parts resembling those of a face? Is it because our brains are hard-wired to detect the presence of a face as quickly as possible, or is it a later cognitive construction or interpretation?
Face perception is an automatic, rapid and subconscious process, already present in human newborns, who preferentially orient towards simple schematic face-like patterns (for review see [2
]). The neural substrate for face processing consists of a distributed network of cortical and subcortical regions. The cortical areas include the inferior occipital gyrus, the fusiform gyrus, the superior temporal sulcus, and the inferior frontal gyrus, while the subcortical network comprises the superior colliculus, the pulvinar nucleus of the thalamus, and the amygdala [4
]. The subcortical route in adults provides residual face-processing abilities in blindsight patients [7
], but the role of this route in the intact brain is not clear.
] and electro-encephalographic studies have demonstrated face perception is accompanied by a signal arising at around 170ms after stimulus onset, the N170 (for review, see [11
]), and this peak of activity has been associated with face identification [12
]. This face-specific component is correlated with activation of the Fusiform Face Area (FFA) and the Superior Temporal Sulcus (STS) [13
]. The face-specificity of this component has however been challenged by a recent study examining the effect of interstimulus perceptual variance (ISPV) ([14
], but see [15
]). In addition to this signal at 170ms, MEG studies have reported an earlier, face-specific activation peaking between 100ms and 120ms after stimulus onset which has been associated with face categorization processes [10
We used MEG to measure brain responses to photographs of faces, objects, and objects that can be interpreted as faces, and determine whether faces perception evoked by these objects is a late cognitive process, or whether it is initiated in the earliest stages of face processing.