Cognitive Psychology Chapter 10

Unilateral Neglect

A condition caused by damage to the parietal lobes Ex. Drawing half of a daisy

Imagery Debate

A debate about whether imagery is based on spatial mechanisms, such as those involved in perception, or on mechanisms related to language, called propositional mechanisms. Started by Pylyshyn.

Spatial Representation

A representation in which different parts of an image can be described as corresponding to specific locations in space.

Conceptual Peg Hypothesis

Created by Paivio- concrete nouns create images that other words can "hang onto."

M.G.S.

Farah and coworkers had M.G.S. perform the mental walk task, in which she imagined walking toward an animal and estimated how close she was when the image began to overflow her visual field. Before the operation, M.G.S. felt she was about 15 feet from an imaginary horse before its image overflowed. But when Farah had her repeat this task after her right occipital lobe had been removed, the distance increased to 35 feet because removing part of the visual cortex reduced the size of her field of view, so the horse filled up the field when she was farther away. This result supports the idea that the visual cortex is important for imagery.

Imageless thought debate

Is thought possible without images?

Early Behaviorists' view of Imagery

It was "mythical", impossible to prove, not worth studying

Propositional Mechanisms

Mechanisms related to language

Glen Lea

Proposed that as subjects scanned, they may have encountered other interesting parts, such as the cabin, and this distraction may have increased their reaction time.

Visual Imagery

Seeing in the absence of visual stimulus

Epiphenomenon

Something that accompanies the real mechanism but is not actually part of the mechanism. Ex. Lights on a computer.

Tacit Knowledge Explanation

Subjects unconsciously use knowledge about the world in making their judgments. (Pylyshyn)

Island Experiment ( Kosslyn)

Subjects were told to imagine an island that contained 7 different locations. By having subjects scan between every possible pair of locations (a total of 21 trips), Kosslyn's results support the idea that visual imagery is spatial

Propositional Representation

A representation in which relationships can be represented by abstract symbols. Ex. The cat is under the table.

Dissociations between Imagery and Perception

Cases have also been reported of dissociations between imagery and perception. Ex1. Cecilia Guariglia and coworkers studied a patient whose brain damage had little effect on his ability to perceive but caused neglect in his mental images (his mental images were limited to only one side) Ex2. R.M. had suffered damage to his occipital and parietal lobes (Farah). R.M. was able to recognize objects and to draw accurate pictures of objects that were placed before him. However, he was unable to draw objects from memory, a task that requires imagery. He also had trouble answering questions that depend on imagery, such as verifying whether the sentence "A grapefruit is larger than an orange" is correct. Ex.3 C.K. could recognize parts of objects but couldn't integrate them into a meaningful whole. But C.K. was able to draw objects from memory, a task that depends on imagery. When he was shown his own drawings after enough time had passed, he had forgotten the actual drawing.

Paired- Associate Learning

Created by Paivio- subjects are presented with pairs of words, like boat-hat or car-house , during a study period. They are then presented, during the test period, with the first word from each pair. Their task is to recall the word that was paired with it during the study period. Thus, if they were presented with the word boat , the correct response would be hat

Mental Chronometry (Shepard & Metzler)

Determining the amount of time needed to carry out various cognitive tasks (Used with rotating spatial figures)

Finke & Pinker

Did the experiment with the dots and arrows to prove that tacit knowledge could not account for all time delays.

Imagery Neurons (Krieman)

Neurons that responded to some objects but not to others- For example, the records show a neuron that responded to a picture of a baseball but did not respond to a picture of a face. Notice that this neuron fired in the same way when the person closed his or her eyes and imagined a baseball (good firing) or a face (no firing). -- these neurons respond in the same way to perceiving an object and to imagining it, thereby supporting the idea of a close relation between perception and imagery.

Alan Paivio

Paivio showed that it was easier to remember concrete nouns, like truck or tree , that can be imaged, than it is to remember abstract nouns, like truth or justice , that are difficult to image.

TMS (Transcranial Magnetic Stimulation) by Kosslyn and Coworkers

Presented TMS to the visual cortex while subjects were carrying out either a perception task or an imagery task. Perception Task- subjects briefly viewed a display and were asked to make a judgment about the stripes in two of the quadrants. Imagery Task- subjects closed their eyes and based their judgments on their mental image of the display. Results- stimulation caused subjects to respond more slowly, and that this slowing effect occurred both for perception and for imagery. Based on these results, Kosslyn concluded that the brain activation that occurs in response to imagery is not an epiphenomenon and that brain activity in the visual cortex plays a causal role in both perception and imagery.

Depictive Representations

Representations that are like realistic pictures of an object, so that parts of the representation correspond to parts of the object. Also in the category of spatial representation. Ex. Diagram of the cat under a table.

Mental Scanning

Subjects create mental images and then scan them in their minds (Kosslyn) Thought that as scanning a boat, reaction time would be slower because they would have to mentally travel the length of the boat.

Conclusions from the Imagery Debate

The idea of shared mechanisms follows from all of the parallels and interactions between perception and imagery. The idea that not all mechanisms are shared follows from some of the fMRI results, which show that the overlap between brain activation is not complete; some of the neuropsychological results, which show dissociations between imagery and perception; and also from differences between the experience of imagery and perception. Perception occurs automatically. Imagery requires effort.

Mental Walk Task (Kosslyn)

They had to imagine that they were walking toward their mental image of an animal. Their task was to estimate how far away they were from the animal when they began to experience "overflow"—when the image filled the visual field or when its edges started becoming fuzzy. The result was that subjects had to move closer for small animals (less than a foot away for a mouse) than for larger animals (about 11 feet away for an elephant), just as they would have to do if they were walking toward actual animals. This result provides further evidence for the idea that images are spatial, just like perception.

Tree Experiment (Ganis and Coworkers)

Used fMRI to test 2 Conditions. Condition 1: Perception- Subjects observed a drawing of an object, such as a tree Condition 2: Imagery- Subjects were told to imagine a picture that they had studied before, when they heard a tone. Results: Thus, there is almost complete overlap of the activation caused by perception and imagery in the front of the brain, but some difference near the back of the brain.

Pegword Technique

You associate items with concrete words using imagery.

H or T Experiment (Farah)

imagine either the letter H or the letter T on a screen- Once they had formed a clear image on the screen, they pressed a button that caused two squares to flash, one after the other. One of the squares contained a target letter, which was either an H or a T. The subjects' task was to indicate whether the letter was in the first square or the second one. The results indicate that the target letter was detected more accurately when the subject had been imagining the same letter rather than the different letter. Farah interpreted this result as showing that perception and imagery share mechanisms;

Mental Imagery

the ability to recreate the sensory world in the absence of physical stimuli (taste, smell, tactile)