Agnosia Overview and Studies

Agnosia - "Not knowing"

• Agnosia is the inability to recognize objects
• Agnosia is a perceptual disorder of recognition

Lissauer (1890)

• Agnosia isn’t a unitary disorder, it has multiple types and levels
• Apperceptive and Associative agnosia

Unconventional Views Test

• Shown multiple objects in different orientations
• Agnosia patients can recognize the object in multiple orientations, as well as other orientations

De Renzi et al (1969)

• De Renzi's study uses a visual matching task
• One object, then several, where one is the match - participant has to pick the match
• Patients successfully recognize matching objects

Warrington & Taylor (1978)

• Warrington and Taylor's model uses the identification of matching objects based on visual properties like: Shape, Size, Color, and Texture
• The model uses visual information to create a perceptual representation of the object

Patient MS (Ratcliff & Newcombe (1982)

• Able to copy objects
• Able to match objects based on visual properties
• Able to give descriptions of the objects
• Unable to recognize or name objects

Patient FRA

• Able to identify objects and copy them
• Unable to name the object
• Unable to match objects based on visual properties

Patient JB

• Able to draw from memory of the object
• Able to provide a verbal description of the object
• Unable to identify the object

Humphres & Riddoch (1984): Two unconventional views

• The model suggests that agnosia is due to a breakdown in visual processing
• The other model suggests that agnosia is a deficit in object representation, even if visual processing is intact

Warrington & James (1986)

• Suggest that it is harder to match objects based on their properties when there is no context

Distinctive features model (Warrington)

• The model proposes that objects are represented by distinctive features
• Features can be both visual or non-visual, and can be perceptual or conceptual
• Perceptual features are based on appearance, while conceptual features are based on function

Hierarchical Processing Approach

• The model suggests that representations of objects are formed through a hierarchical process:
• Features are combined to form objects are combined to form objects which are combined to form categories

Two routes to object constancy

• The dorsal stream - involved in spatial processing - used for visual guidance of action
• The ventral stream - involved in object recognition - used for conscious awareness of object properties

Face inversion effect

• Faces are harder to recognize when they are upside down
• This suggests that face recognition is based on processing specific features
• Face recognition is not just based on basic visual features

Unteroffizier S (Bodamer, 1947)

• Unable to recognize people’s faces, even faces of family members
• Prosopagnosia - inability to recognize faces
• Could recognize people by voices and other features

Mr.W (Bruyer et al., 1983)

• Able to recognize familiar faces while looking at them directly
• Unable to recognize familiar faces when seeing them in photos
• Could recognize familiar faces when seeing them in videos

Model of face processing - Bruce and Young (1986)

• The model proposes that face processing is a hierarchical process that involves different stages of processing
• First stage involves encoding face features which are then used to create a representation of the face
• This representation is then used to access information about the person

Covert Recognition in Prosopagnosia

• Covert recognition is the ability to recognize faces without conscious awareness
• Patients may not be able to say who they are seeing but their physiological responses show that they are recognizing the face.

Tranel & Damasio (1988)

• Tranel & Damasio devised a study to test covert recognition in prosopagnosic patients
• The study used a familiarity rating scale to assess the patients’ ability to recognize faces

Patient PH

• Patient PH was unable to recognize the faces of family members
• The patient's physiological responses showed that they were recognizing the faces of family members

Are faces special?

• Face recognition is a type of object recognition
• Faces are a type of object
• Face recognition is a specialized form of object recognition
• It is harder to recognize faces than other types of objects

McNeil & Washington - Patient WJ

• Patient WJ showed that prosopagnosia can be selective impairment because WJ's face recognition was impaired but his recognition of other objects was unaffected

Developmental perspective on Face Expertise

• From birth to age 3, infants develop the ability to recognize faces, but they don't become experts at face recognition until adolescence
• In adolescence, the ability to recognize individual faces improves

Two pathways to see faces

• The dorsal stream is involved in extracting information about the spatial relationship between objects and the observer
• The ventral stream is involved in recognizing objects

Blindsight

• Blindsight is the ability to detect visual stimuli without conscious awareness
• Patients may be able to detect or locate the stimuli even if they don't see it

Poppel et al.(1973)

• The experiment tested the hypothesis that people with cortical blindness can respond to stimuli even if they are unable to see them

Patient DB (Weiskrantz, 1986)

• Patient DB was able to detect the movement of stimuli but they were unable to see them

Patient GY (Weiskrantz et al. 1995)

• Patient GY was able to detect the movement of stimuli even when they were unaware of their presence

Challenges to Blindsight

• The claim that blindsight supports the existence of unconscious processing is a problematic claim, even within the theoretical frameworks that it is supposed to support
• The idea that blindsight is a genuine visual experience is also problematic because it's unclear how one could have a visual experience without being conscious of it

Potential pathways supporting Blindsight

• The dorsal stream is involved in spatial processing
• The ventral stream is involved in object recognition

Form Discrimination in DB (focus on ventral stream)

• Patient DB showed a higher level of performance when the stimuli were located in the middle of the visual field

Prime Sight in DB

• Presenting a prime stimulus before the target stimulus can affect the perception of a target when the target was presented in the same location as the prime

Golden Age 1

• 1870-90s
• Psychologists wanted to understand and measure mental processes

Diagram makers

• Used to denote the location of psychological processing
• They depict simple concepts of the mind

1960s - cognitive revolution 2nd Golden Age

• The revolution involved focusing on cognitive functions, such as attention, memory, and language
• New experimental techniques were developed

Patient Populations

• Patients with brain damage helped to unravel how the brain works
• Patients with different brain damage patterns could show different disorders
• This allowed researchers to understand how the brain is organized

Explore the concept of agnosia, a perceptual disorder characterized by the inability to recognize objects. This quiz delves into various studies and classifications of agnosia, including insights from notable researchers like Lissauer, De Renzi, and Warrington & Taylor. Test your understanding of different types and models related to this intriguing disorder.