Face Processing Flashcards
What is Prosopagnosia?
‘Face blindness’. A lack of knowledge about faces. More like ‘face-identity blindness’, it is the impaired ability to recognise faces. It can be acquired or congenital
How is prosopagnosia acquired?
Typically from damage to the occipito-temporal lobes, and usually this is around the fusiform gyrus
What are examples of direct tests of overt face recognition?
Unfamiliar face matching. Forced-choice judgements or ratings of familiarity. Identifying occupation of familiar or famous people. Naming familiar or famous people
Why are there also indirect tests of face processing?
To test if people process faces even though they are unaware
What is an example of an indirect test of overt face recognition?
Semantic priming. Priming is where the exposure to a stimulus influences response to a subsequent stimulus, and semantic priming is when the prime and target are from the same semantic category and share features
What is an example of how semantic priming could work?
Judging familiarity of printed names, when each name is preceded by a name or face that is semantically related, neutral or unrelated to the target name. RT is quicker when with related prime and slowest for unrelated prime
What is an example of covert face recognition in prosopagnosia?
PH could match unfamiliar faces so he did not have a structural encoding problem and could recognise names and voices of familiar people, so not a person identity impairment. RTs for familiar where shorter than unfamiliar faces in matching task for PH and healthy controls. With priming, quicker RT with semantic related name when prime shown before face (De Haan, Young and Newcombe 1987)
How can the results of studies with patients with prosopagnosia be explained?
Patients have access to information about facial identity but do not consciously know they have this access and cannot volunteer this knowledge. Dissociation of awareness and knowledge. However, bit all prosopagnosiacs show evidence of covert recognition, and don’t all show same or similar RT results as PH
What are ways of presenting stimuli subliminally?
Very brief presentations and masking, binocular rivalry, repetition/continuous flash suppression (CFS), breaking continuous flash suppression (b-CFS)
What is visual backward masking?
The reduction or elimination of the visibility of one brief stim ulus by the presentation of a second brief (mask) stimulus
What does the effectiveness of masking depend on?
Timing (of target and mask), target stimulus (shape, size, luminance, overlap with mask etc), mask type (noise vs pattern etc) and parameters (as with target stimulus), display parameters (such as luminance and wavelength of background) and task
What are examples of very brief presentations and masking?
Differential facial EMG responses to unconsciously perceived facial expressions (Dimberg et al 2000). Face vs blank screen detection and fearful vs neutral face discrimination (Williams et al 2004). Fearful and happy faces for 33ms followed by neutral face masks for 167ms and patients reported seeing only neutral faces - amygdala activation measured (Whalen et al 1998)
What is binocular rivalry?
Two stimuli are presented, one to each eye and perception alternates. Stimulus remains the same but the conscious percept varies
What is an example of an fMRI study with binocular rivalry?
Williams et al 2004 - both FFA and PPA showed increased activity when their preferred image type was dominant relative to when it was supressed
What is an example of interocular/continuous flash suppression?
Tsuchiya and Koch 2005 - one eye presented with moving visual pattern, other shown stationary image which is typically suppressed from awareness
