Tutorial 6: Processing of faces (Prosopagnosia)

Question 1

What is prosopagnosia?

Answer 1

The selective impairment in the ability to recognize or differentiate among faces.
‘Face blindness’

Disorder of face recognition
Familiar faces (not remembering faces of family, friends, etc)
Unfamiliar faces (unable to remember faces of new people)

Recognition of other objects often unimpaired
Can occur with or without object agnosia

Question 2

Two forms of prosopagnosia:

Answer 2

1. Acquired - caused by acute brain damage (damage to the occipito-temporal cortex).
2. Developmental (congenital) - inherited.

Question 3

Right Fusiform Gyrus

aka Fusiform Face Area (FFA)

Answer 3

The fusiform face area is specialised for processing faces because it shows preferential activity for faces beyond other common objects.

Question 4

Famous Faces Test

Answer 4

• Assesses memory for facial identity.
• All pictures had hairclothing and any other non-face information removed.
• Method: Subjects were presented with pictures of 60 famous faces, for 5 seconds each.
• Task: They had to name the face, or report unique identifying info of that face.
• Results: PPGs impaired relative to controls, BUT could be a face memory problem OR because Ps lack familiarity with people in pop culture.

Question 5

Cambridge Face Memory Test

Answer 5

Uses new faces that the participants have to remember.

• Given images of target faces to learn.
• Presented with one target face and two distractor faces in novel positions.
• Which have you seen before?
• Ss must learn to recognise 6 novel target faces. Each of these is presented from 3 viewpoints, in progressively difficult stages.
• Task: Introductory phase: Each target face was presented in three views, The subjects were presented with 3 forced-choice items: one of the study images and two novel faces in the same pose.
• Test phase: comprised of 54 forced-choice items. Each was a novel view of the six target faces and two non-target faces. These items were more difficult because unfamiliar views were used and some had ‘noise’.
• Results: The family members were significantly worse than the controls at identification of the target faces.
• Unclear whether the deficits are purely memory problems, OR problems at earlier stages processing facial identity (i.e., perceiving the identity in the first place) because such perceptual problems would prevent encoding a good memory.

Question 6

Cambridge Face Perception Test

Answer 6

• Arrange six morphed faces in order of similarity to the target face.
• Done with upright AND inverted faces
• Prosopagnosics perform worse than controls in upright and inverted conditions.
• Conclusion: Facial identity perception impairment for prosopagnosic family. Not just memory impairment.

Question 7

Mind in the Eyes Test

Answer 7

• 36 items – eye region and 4 emotion state words.
• Choose which word best describes the eyes. No time limit.
• Subtle discriminations required – challenging.
• Prosopagnosics displays normal processing of facial emotions. More evidence that perception of facial identity is dissociable from perception of facial emotion.

Question 8

Within-Category Object Recognition Test

Answer 8

• Shown a series of objects (faces, cars, or guns)
• Shown this set of items intermingled with new ones
• Say ‘old’ or ‘new’ to each item (recognition memory)
• Tests recognition memory of individual items within a broader category.
• Prosopagnosics have deficits in within-category identification of non-face objects, not just for faces, although it seems to a lesser extent.

Question 9

Global-Local Task

Answer 9

• Shown displays that contain one big (global) letter made up of lots of small (local) letters.
• Must identify EITHER the large or small letter depending on instructions.
• Global and local letters either match (consistent trials) or mismatch (inconsistent trials).
• ## No evidence of global processing impairment for prosopagnosics