When a Bowl Becomes a Face
Wardle and colleagues on illusory faces in objects: how can the same image remain both a face and an object?
Our results reveal the representation of natural errors of face detection in the human brain. With fMRI and multivariate pattern classification methods, we found that a face-like response to illusory faces was restricted to face-selective regions in occipital–temporal cortex. In scene and object areas, illusory faces were instead represented more similarly to objects.
Exploiting the much higher temporal resolution of MEG, we showed that illusory faces are initially represented as more face-like in their brain activation patterns than similar matched objects. However, only ~100 ms later, illusory faces are represented as more object-like, consistent with a rapid resolution of the detection error.
Thus, although illusory faces in objects are perceived as having a persistent dual identity (face, object), their neural representation quickly shifts in its relative weighting of these two identities over time. This is consistent with the rapid activation of a broadly tuned face-detection system, which is tolerant of substantial visual variance in the definition of facial features.
Following the initial face-detection process, which possibly occurs via a subcortical route, the subsequent resolution of the error is likely driven by processing in cortical areas involved in face recognition.