Attention Part 2Page 89 - 107

What Happens to Unattended Stimuli?

Evidence from Neglect Patients.Shown some pictures to the non-neglected visual field and others to the neglected visual field.Later asked to identify the same pictures in a degraded version. They are just as fast with those that had been presented to the neglected as the non-neglected visual field (priming).

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Neurological evidence also indicates that when the overall attentional load of a task was low, neglect patients showed increased brain activity to task irrelevant items presented in the neglected visual field (some processing is going on) even though the patients are not consciously aware of the stimuli.

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Hemi neglectPatients Suffering From 'Hemi-neglect' Ignore Things On Their Left, But They See Them Nonetheless

Click here to see Science Daily article (05/15/08.)This study demonstrates that in hemi-neglect the left part of the world is not a 'blind' region: in a way, patients read unconsciously what is there. However, the patients cannot make conscious use of this information

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Attention as Capacity• Attention is the process of allocating mental resources

to various cognitive tasks

Factors effecting allocation of Attention-Anxiety -Salience and Distinctiveness- Relevance-Task demands

Cross- Modality Effects

Ventriloquist IllusionRubber Hand Illusion

Phantom Limb Pain (begin at 13:00)

Body Swap Illusion

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Disorders of Visual Attention

Hemi-neglect – (Historical note) President Woodrow Wilson after suffering two strokes developed hemi neglect. When colleagues came to visit him, he failed to respond to them until they were escorted to his right side. He denied he had a problem and planned to run for a third term as president until his wife finally intervened.

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Spatial Extinction: can detect a single item in both the left and right visual fields but, under conditions of double simultaneous stimulation they fail to detect the item in the left field.

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Presented

Perceived

When stimuli is presented in the neglected field but has no competition for attention from the non-neglected visual field, the image is perceived. When there is competition for attention from the non-neglected visual field, attention is given only to the non-neglected visual field.

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Two Attention Systems (Corbetta)

Goal directed system - preparing and applying goal-directed (top-down) selection for stimuli and responses. Effected by expectations, knowledge and/or intentions.

Stimulus driven – (bottom-up) specialized for the detection of behaviorally relevant stimuli, particularly when they are salient or unexpected. Circuit breaker .

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The area were the two attention systems combine is in the parietal lobe. There is competition for attention from the two attentional systems. Hemi- neglect can occur due to impairment in either the goal-directed or the stimulus driven systems. Results in a failure to activate the parietal cortex enough to capture attention to that visual filed.Hemi-neglect is a disorder of Attention – not of perception.

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Reducing Neglect: Physiotherapy

Hemi-neglect patients when asked to point straight ahead – point several degrees to the left.

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Prism glasses that shift the visual field 10 degrees to the right allow patients to use the Goal-directed (top-down) processes to direct more attention to the neglected left visual field.

Demonstration• I will show you a scene quickly.• Report first the black numbers.• Report what you see at each of the 4 locations.

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Mask

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• Report first the black numbers.• Report what you saw at each of the 4 locations.

Illusionary conjunctions

• We tend to put different features from different objects together.

• Some brain damaged patients (parietal lobe) show illusionary conjunctions even when the patients were allowed to view the stimuli for 10 seconds.

Feature search

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Conjunction searchTreisman & Gelade 1980

Feature Integration Theory

Find the Green X

Find Which is more difficult?

Find Which is more difficult?

Typical Findings & interpretation

• Feature targets pop out• flat display size function

• Conjunction targets demand serial search

• non-zero slope

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Feature integration theory

• Attention is the “glue” that combines the information from the what and where systems.

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Multi-tasking

Ophir et al (2009) Correlation between multitasking and distractibility.When asked to do two tasks at once, participants who reported being multitaskers performed less well on the main task than did non-multitaskers. Perhaps multi-taskers are just less able to focus attention.

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Cell Phone Use

Hyman et al (2009)Cell phone users less likely (25%) than non-users (51%) to notice a unicyling clown!!!

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Practice and Dual Task Performance

Spelke, Neisser et al (1976)Two subjects read short stories while writing lists of words at dictation. After some weeks of practice, they were able to write words, discover relations among dictated words, and categorize words for meaning, while reading for comprehension at normal speed. The performance of these subjects is not consistent with the notion that there are fixed limits to attentional capacity.

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Automatic vs. Controlled

• Automatic Processes• Fast and efficient• Unavailable to

consciousness• Unavoidable• Unintentional • Controlled Processes

• Slow and less efficient• Available to consciousness• Controllable• Intentional

Attention as executive control

• In contrast to capacity theories (which see attention as a limitation) considering it as executive control of possibly conflicting multiple goals makes attention instead a source of efficiency

• Evidence: Psychological Refractory Period

Psychological Refractory Period

• 2 stimuli and 2 responses• Light: press button• Tone: press foot pedal

• Varying SOAs• At short SOAs, response to task 2 takes longer

• Varying stimulus processing difficulty• Lengthening processing of stimulus 1 slows RT to stimulus 2• Lengthening processing of stimulus 2 does not slow response to stimulus 2!!

PRP: Surprising Results

S1 R1

ProcessingOf Stimulus

Central Executive

Response to Stimulus

S2 R2

S1 R1S2 R2

S1 R1S2 R2