Are Faces Special?
Are faces special? Critically evaluate the evidence that we have evolved a specialised neural network dedicated to processing faces. Brian Marron, 11461992, SF TSM.
Processing faces is extremely important to humans as social beings. We are able to put and identity on thousands of faces (Gazzaniga, 2002) with ease, something we might take for granted. The value of this ability can be better understood when the world is viewed through the eyes of somebody with prosopagnosia, the inability to recognise faces. The following quotation from David Fine, a prosopagnosic describing the difficulty associated with the disorder.
“I often fail to recognise my children or even my wife … I have failed to acknowledge friends and, more
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The logic is this: if a brain region is damaged and face processing is hindered with all other non-face processing remaining unhindered, then surely that is strong evidence for a specialised neural network dedicated to processing faces only. (Hole & Byrne, 2010) i.e. A double-dissociation must be shown between face and non-face stimuli. Prosopagnosia patients are the most promising hopes for meeting those criteria just outlined (Gazzaniga, 2002). It is seldom that a prosopagnosia patient does not show impairments to non-face-stimulus processing abilities. This is thought to be because traumatic brain injuries resulting in prosopagnosia are usually wide-ranging (Farah et al, 1995). However, there are some cases of ‘pure’ prosopagnosia who have no non-face processing impairments (Wada & Yamatoto, 2001). For the evidence to be valid, they must make within-class discriminations to make the test comparable with face processing tests. This within-class double dissociation has been found in many object classes like cars (Rossion et al, 2003), glasses (Farah et al, 1995) fruit (Riddoch et al, 2008) and more. There is even evidence for a double dissociation between human and animal face-processing. There is the case of a sheep farmer, WJ (McNeil & Warrington, 1993). WJ suffered from prosopagnosia yet he was able to identify his sheep. Another case of a prosopagnosic farmer being able to identify his animals was reported by Bruyer et al. (1983). The double dissociation is made