Face recognition and visual agnosias



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FACE RECOGNITION AND VISUAL AGNOSIAS



To read up on face recognition and visual agnosias, refer to pages 101–113 of Eysenck’s A2 Level Psychology.

Ask yourself


  • What would it be like to be unable to recognise your friends and family?

  • Are faces more difficult to recognise than objects?

  • What do you think is the most common cause of visual agnosias?



What you need to know


PROSOPAGNOSIA

BRUCE AND YOUNG

VISUAL AGNOSIAS

  • Research into prosopagnosia and the effects of the condition

  • Processes involved in face and object recognition

  • Bruce and Young’s (1986) theory of face recognition

  • Apperceptive agnosia

  • Associative agnosia



PROSOPAGNOSIA


This is the inability to recognise faces, even ones that are very familiar such as those of friends and family. Thus, this condition is also know as “face blindness” and is usually caused by brain damage. Most prosopagnosics can recognise objects reasonably well but do have some problems with object recognition.

Prospopagnosia is difficult to investigate due to a number of problems, including the fact that face and object recognition vary from patient to patient; face recognition may be much harder than object recognition but we cannot be sure if this is the explanation. The origins of the condition may vary depending on whether the prosopagnosia is acquired (due to brain damage) or developmental. Most research has involved acquired prosopagnosia, and relatively little is known about developmental prosopagnosia. Prosopagnosics may be able to process faces below the conscious level. This is called semantic priming and is where a name is recognised more rapidly when preceded by a related face than by an unrelated one. Some prosopagnosics show semantic priming in spite of not recognising the face (Young, Hallawell, & de Haan, 1988, see A2 Level Psychology page 102) and this suggests that face processing occurred below the conscious level.


RESEARCH EVIDENCE INTO PROSOPAGNOSIA

  • The ability to recognise faces but not objects or vice versa is known as double dissociation, and would strongly suggest that face recognition and object recognition rely on different processes. Duchaine and Nakayma (2005, see A2 Level Psychology page 103) found that the prosopagnosics performed in the normal range on all (or nearly all) of the non-face tasks.

  • Moscovitch, Winocur, and Behrmann (1997, see A2 Level Psychology page 103) studied CK, a man with impaired object recognition. He performed as well as controls on face-recognition tasks regardless of whether the face was a photograph, a caricature, or a cartoon provided it was upright and the internal features were in the correct locations.

  • Evidence suggests that the fusiform face area (especially the one in the right hemisphere) is specialised for processing faces. Prosopagnosics typically have damage to this brain region (Farah, Tanaka, & Drain, 1995, see A2 Level Psychology page 103). Further support is provided by Downing et al. (2006, see A2 Level Psychology page 103) who presented participants with faces, scenes, and 18 object categories (e.g. tools, fruits, vegetables). The fusiform face area responded significantly more strongly to faces than to any of the other 19 stimulus categories. However, Grill-Spector, Sayres, and Ress (2006, see A2 Level Psychology page 103) suggest the fusiform specialisation may not be so pronounced. In this study observers saw faces and three categories of objects (animals, cars, and abstract sculptures). More elements in the fusiform face area responded to faces than to any of the other types of objects, but the differences were not very large.

  • Gauthier and Tarr (2002 see A2 Level Psychology page 104) suggest there are two reasons why faces appear special even though they aren’t. First, we typically recognise faces at the individual level, whereas we often recognise objects at a more general level. Recognising specific examples of a category (i.e. faces) is harder than recognising the general category to which an object belongs. Second, nearly all of us have considerably more experience (and thus expertise) in recognising faces than in recognising individual members of most other categories. Thus, Gauthier and Tarr concluded that the fusiform face area is a brain area we use for any objects for which we possess expertise not just for processing faces.

  • Evidence against this general specialisation of the fusiform area of the brain is that when it is damaged the individual should no longer be able to acquire any expertise of specific objects. Yet one prosopagnosic, WJ, acquired a flock of sheep. Two years later, his ability to recognise individual sheep was as good as that of healthy controls with comparable knowledge of sheep (Sergent & Signoret, 1992, see A2 Level Psychology page 104).



EVALUATION OF EVIDENCE INTO PROSOPAGNOSIA

  • Most people do possess much more expertise about faces than almost any other object category as predicted by the expertise theory. We have more experience of identifying individual faces than individual members of most other categories. It thus seems possible that differences between face and object recognition might be attributable to differences in expertise.

  • The greatest limitation is that none of the specific hypotheses of the expertise theory has been supported. The fusiform area is not consistently more active when recognising specific objects in the way that it is when recognising faces. It seems then that the processes involved in face recognition differ substantially from those involved in object recognition.



BRUCE AND YOUNG


A close study of brain-damaged individuals has told us much about the processes involved in face recognition. Bruce and Young’s (1986, see A2 Level Psychology pages 105–108) theory of face recognition suggests that we extract several kinds of information from faces. They identified eight components of face recognition (see figure in A2 Level Psychology page 105):

  1. Structural encoding: This produces various representations or descriptions of faces.

  2. Expression analysis: People’s emotional states are inferred from their facial features.

  3. Facial speech analysis: Speech perception is helped by observing a speaker’s lip movements. This was shown clearly by McGurk and MacDonald (1976, see A2 Level Psychology page 105), who prepared a tape in synchronisation with lip movements indicating “ba”. Participants heard “da”, which is a blending of the visual and auditory information.

  4. Directed visual processing: Specific facial information is processed selectively.

  5. Face recognition nodes: These contain structural information about known faces.

  6. Person identity nodes: These contain structural information about known faces.

  7. Name generation: A person’s name is stored separately.

  8. Cognitive system: This contains additional information (e.g. most actors and actresses have attractive faces), and influences which other components receive attention.

A more simplified theory is provided by Duchaine and Nakayama (2006, see A2 Level Psychology page 106) who included an additional face detection stage (see figure in A2 Level Psychology page 106) and then a further three more components, and so about half the number proposed by Bruce and Young (1986).

Bruce and Young (1986) suggest that familiar and unfamiliar faces are recognised in different ways. Recognising familiar faces depends mainly on structural encoding, face recognition units, person identity nodes, and name generation. In contrast, the processing of unfamiliar faces involves structural encoding, expression analysis, facial speech analysis, and directed visual processing. If different processes are involved then some patients should have much better face recognition for familiar than for unfamiliar faces, whereas other patients should have the opposite pattern (i.e. a double dissociation).

Similarly, the model predicts that separate processing should be used for the processing of facial identity (who is the person?) and the processing of facial expression (e.g. what is he/she feeling?). Again a double dissociation would provide evidence that the two tasks involve different processes. The processes involved in facial speech analysis (using lip movement to facilitate speech perception), according to the model, differ from those used in other aspects of face processing. The model also predicts that when we look at a familiar face, familiarity information from the face recognition unit should be accessed first, followed by information about that person (e.g. occupation) from the person identity node, followed by that person’s name from the name generation component. Therefore, the face should be recognised before other information about the individual is accessed.


Research evidence into Bruce and Young’s theory

  • The evidence does not provide much support for double dissociation in terms of good recognition of familiar faces and poor recognition of unfamiliar faces. Young et al. (1993, see A2 Level Psychology page 107) studied 34 brain-damaged men. There was only weak evidence for selective impairment of either familiar or unfamiliar face recognition.

  • Research supports the assumption that separate routes are involved in the processing of facial identity (i.e. face recognition) and facial expression. For example, Humphreys, Avidan, and Behrmann (2007, see A2 Level Psychology page 107) studied three participants with developmental prosopagnosia (in which there is no obvious brain damage). All three had poor ability to recognise faces, but their ability to recognise facial expressions (even the most subtle ones) was comparable to that of healthy individuals. Calder et al. (2000, see A2 Level Psychology page 107) provide further support for separate processing.

  • Campbell, Landis, and Regard (1986, see A2 Level Psychology page 107) studied a woman with prosopagnosia who couldn’t recognise faces but could work out which phonemes were being mouthed when looking at photographs of faces. This supports the prediction that there are separate processes for facial speech analysis and facial identity.

  • Young et al. (1986, see A2 Level Psychology page 107) found the decision as to whether a face was familiar was made faster than the decision as to whether it was a politician’s face. Kampf, Nachson, and Babkoff (2002, see A2 Level Psychology page 107) found as predicted that participants categorised familiar faces with respect to occupation faster than they could name the same faces, a finding that has also been reported by several other researchers. This supports the prediction that face recognition preceded occupation identification, which preceded naming of the stimulus.

  • Young, Hay, and Ellis (1985, see A2 Level Psychology page 108) asked people to keep a diary record of problems they experienced in face recognition. There were 1008 incidents in total, but people never reported putting a name to a face while knowing nothing else about that person. This supports the prediction that we cannot put a name to a face without also having available other information about that person (e.g. his/her occupation).

  • Brédart et al. (2005, see A2 Level Psychology page 108) presented members of a Cognitive Science Department with the faces of close colleagues and asked them to name the face or to indicate the highest degree the person had obtained. Naming times were faster than the times taken to provide the person information about educational level (832 ms vs. 1033 ms, respectively), which is opposite to the theory’s prediction. However, this is probably due to the high frequency of exposure to the names of close colleagues.



Evaluation of the evidence into Bruce and Young’s theory

  • Improved our understanding. Bruce and Young have provided a great deal of insight into the wide range of information that can be extracted from faces. The theory has contributed greatly to our understanding of the various problems with different aspects of face recognition shown by brain-damaged patients.

  • Empirical support. The different predictions have received empirical support such as the prediction that separate processing routes are involved in the processing of facial identity and facial expression. There is also evidence of differences in the processing of familiar and unfamiliar faces, and that the processing of familiar faces typically leads first to accessing of familiarity information, followed by personal information, and then finally name information.

  • Oversimplified. The theory ignores the initial face detection stage.

  • Processes are unlikely to be completely separate. The great majority of prosopagnosics have severe problems with processing facial expression as well as facial identity, suggesting that the two processing routes are only partially separate. Even the processing of emotions may consist of different processes because patients with impaired processing of facial expression sometimes have much greater problems with one emotional category (e.g. fear; disgust) than others. This suggests that there is not a single system for facial expressions.

  • Inflexible. It is too inflexible in the assumption that the processing of names always occurs after the processing of other personal information about faces.

  • Case studies. The research has used the case study method, which means sample size is limited and so the findings may lack generalisability.



VISUAL AGNOSIAS


Visual agnosias is used to refer to various conditions in which brain-damaged patients have difficulty in recognising or identifying objects. Patients with a visual agnosia generally have much stored information about objects. As a result, they can identify objects by touching them, and they can provide detailed verbal descriptions of objects when asked to do so.

Lissauer (1890, see A2 Level Psychology page 109) has identified two main types of visual agnosia:


(1) Apperceptive agnosia: Object recognition is impaired mainly because the patient has problems with complex perceptual processing.
(2) Associative agnosia: Perceptual processes are more or less intact. However, object recognition is impaired because the patients can’t access their relevant stored information about visually presented objects, i.e. they cannot access the information in their long-term memory.

One way to assess the type of agnosia the patient has is to test the patient’s ability to copy objects that can’t be recognised (Humphreys, 1999, see A2 Level Psychology page 109). Patients who can copy objects are said to have associative agnosia, and those who can’t have apperceptive agnosia.


Apperceptive Agnosia

Patients with apperceptive agnosia do possess some perceptual abilities. For example, they typically have normal visual acuity and can reach for moving targets. However, they have deficient visual processes because they are very poor at recognising or identifying objects.
Research evidence

  • Grossman, Galetta, and D’Esposito (1997, see A2 Level Psychology page 110) reviewed previous research on apperceptive agnosia. One patient could only describe a circle as “lots of dots”, and another couldn’t discriminate between an “X” and an “O”.

  • Grossman et al. (1997, see A2 Level Psychology page 110) studied two patients, SZ, a 54-year-old male accountant, and AP, a 65-year-old female teacher. Both of these patients could recognise regular geometric shapes and colours in spite of their severely impaired ability to recognise common objects. However, they were very poor at recognising more complex shapes or when geometric shapes were presented upside down.

  • Humphreys and Riddoch (1987, see A2 Level Psychology page 110) studied a different form of agnosia, in which the person has great difficulty in combining or integrating an object’s features during object recognition, and so it is called integrative agnosia. It is somewhere between apperceptive and associative agnosia, but perhaps closer to apperceptive agnosia. The patient HJA was much better at recognising objects individually than when they were presented with other objects because he had very poor ability to separate out shapes.



Associative Agnosia

Patients with associative agnosia have reasonably good basic perceptual processes but are poor at accessing their stored semantic knowledge about objects because it is hard for them to access in long-term memory.
Research evidence

  • Anaki et al. (2007, see A2 Level Psychology page 111) described their patient (DBO) who had experienced brain damage to the left occipital lobe of the brain (at the back). He had severe visual agnosia as shown by his ability to name only 1 out of 20 common objects. In spite of his visual agnosia, DBO performed well on various tasks involving aspects of object recognition. The fact that he still possessed several visual perceptual skills indicated that he had associative rather than apperceptive agnosia.



Evaluation

  • Empirical evidence supports variations. The empirical research provides convincing evidence that the precise nature of visual agnosia varies considerably from one patient to another.

  • Individual differences. The distinction between apperceptive and associative agnosia accounts for some individual differences. However, it is oversimplified to try to categorise into just apperceptive or associative agnosia. For example, it is not easy to categorise integrative agnosics as having either apperceptive or associative agnosia

  • Lack a clear understanding of the cause. It is generally assumed that the main problem in associative agnosia lies in accessing the stored information about objects that they possess. However, it is hard to obtain clear evidence that that is in fact the main problem.

  • The distinction lacks relevance to specific deficits. The distinction between apperceptive and associative agnosia is more relevant to general deficits in object recognition than specific deficits. For example, prosopagnosics are generally reasonably good at object recognition for most objects other than faces.



So what does this mean?


Prosopagnosia is known as “face blindness” and is usually caused by brain damage. Research suggests that face recognition and object recognition rely on different processes.

Bruce and Young have provided a complex and detailed account of how there are many forms of visual processing in face recognition. They have provided a great deal of insight into the wide range of information that can be extracted from faces. The theory has contributed greatly to our understanding of the various problems with different aspects of face recognition shown by brain-damaged patients. There is empirical support for the different predictions, however the processes are unlikely to be completely separate.



Two further types of visual agnosias include apperceptive agnosia and associative agnosia; apperceptive is a greater deficit. The distinction between apperceptive and associative agnosia accounts for some individual differences. However, it is oversimplified to try to categorise into just apperceptive or associative agnosia. For example, it is not easy to categorise integrative agnosics as having either apperceptive or associative agnosia

Over to you


1. Outline and evaluate Bruce and Young’s theory of face recognition. (25 marks)


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