A Return to the Gorilla What Effects What

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1 A Return to the Gorilla What Effects What We Attend to and What We Don t Simons and Chabis found that although only 43% of people noticed the gorilla, there was no way to predict who would and who would not. It did not seem to be a matter of individual differences, rather it was situational.

2 A Return to the Gorilla What Effects What We Attend to and What We Don t According to Eysenck and Keane (2011), Simons and Chabis did another similar experiment to the invisible gorilla experiment, but in this one, the participants had to count the number of passes made by either the team in black or the team in white. Out of the participants who were counting passes on the white team, only 42% saw the gorilla, but for the participants who counted passes on the black team, 83% of them saw the gorilla. "This shows the impact of similarity between the unexpected stimulus (gorilla) and task-relevant stimuli (members of the attended team)," note Eysenck and Keane.

3 Two Attention Systems (Corbetta & Shulman 2002) Goal directed system - (Ventral system) preparing and applying goal-directed (top-down) selection for stimuli and responses. Effected by expectations, knowledge and/or intentions. Stimulus driven (dorsal system; bottom-up) specialized for the detection of behaviorally relevant stimuli, particularly when they are salient or unexpected. Circuit breaker - grabs out attention. cogch3 Attention 3

4 Change Blindness Inattentional Blindness

5 Change Blindness Change Blindness Demo cogch2 pt 2 5

6 Detection more likely if the changed object received attention (fixated) before it changes. Other researchers have discovered that mental processing in change blindness begins even before the change is presented. More specifically, there is increased brain activity in the parietal lobe (Dorsal pathway) prior to the emergence of a change in a change blindness task.

7 Mindsight change blindness revisited About 1/3 of participants can detect THAT a change is happening before or without being able to WHAT is changing. It was not the same 1/3 who were able to do this (Enright, 2006). Like inattentional blindness it appears to be situational, the dorsal pathway either responds to the change or does not.

8 Does Perception Require Conscious Awareness? Subliminal Perception Limen = subjective threshold. Subjective vs. Objective threshold Subliminal Perception: occurs when a stimulus is too weak to be perceived yet a person is influenced by it.

9 Subliminal Perception

10 Repitition Priming Naccache et al. (2002) Task: Decide as quickly as possible if the letter presented is larger or smaller than 5. Masked (Subliminal) Prime preceded the visible presentation.

11 Participants reported no conscious perception of the prime. However, their performance on the task indicated that they were effected by the subliminal prime. Congruent condition - both prime and visible digit produce same answer. Incongruent condition - prime and visible digit produce different answer. The incongruent prime condition slower than congruent.

12 Corteen & Wood (1972): Experiment in which participants were first given mild shocks whenever certain words--city names--were presented in a long list. This set up a conditioned autonomic response, the galvanic skin response or GSR, which measures changes in the resistance of the skin with sweating. After training, just seeing the city name increased GSR. Then participants SHADOWED prose in one ear and heard a list of words in the other. The list included the city names plus new city names, and neutral words. Measured GSR. cogch3 Attention 12

13 Participant produced a GSR even though they were not consciously aware of the city names being presented. Participants also showed GSR responses to city names that were not conditioned. Shows that the effect generalized to semantically similar words (similar in meaning).

14 How Long Does the Objective Effect Last Lexical Priming Procedure Stimulus flashed for a split second then quickly masked with another stimulus. e.g. Doctor Then a target stimuli is shown either an unrelated word (e.g., bread), a related word (e.g. nurse) or a letter string (djotr).

15 Lexical Decision Task (is target a word?) If the priming stimulus bears a close relationship to the target word, the subject can respond slightly faster. This is a subliminal effect, because the priming stimulus cannot be seen consciously, and subjects cannot report what it is. However, the effect lasts only a tenth of a second (Greenwald, Draine, & Abrams, 1996).

16 Attention Disorders Hemineglect AKA unilateral neglect, hemispatial neglect, hemiagnosia, spatial neglect, contralateral neglect, unilateral visual inattention, hemiinattention, neglect syndrome and contralateral hemispatialagnosia

17 Hemineglect is an unawareness or unresponsiveness to objects, people, and other stimuli Video - Neglect is most prominent and long-lasting after damage to the right Parietal lobe of the human brain, particularly following a stroke. - sometimes patients even ignore or disown their own left limbs - it is not that the patient can't see the stimuli, but rather that they have lost the ability to attend to them or respond to them.

18 Case Study Neglect Patient

19 Disorders of Visual Attention Hemi-neglect (Historical note) President Woodrow Wilson after suffering two strokes developed hemineglect. 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. cogch3 Attention 19

20 What Happens to Unattended Stimuli? Shown some pictures to the nonneglected 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). cogch3 Attention 20

21 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. cogch3 Attention 21

22 Spatial Extinction (milder form of hemineglect) 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. Presented Perceived cogch3 Attention 22

23 When stimuli is presented in the neglected field but has no competition for attention from the nonneglected visual field, the image is perceived. When there is competition for attention from the nonneglected visual field, attention is given only to the non-neglected visual field. cogch3 Attention 23

24 The area were the two attention systems combine is in the parietal lobe. There is competition for attention from the two attentional systems. Hemineglect 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. cogch3 Attention 24

25 Reducing Neglect: Physiotherapy Hemineglect patients when asked to point straight ahead point several degrees to the left. 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. cogch3 Attention 25