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Chapter 4

PSYB57 - Cognition Ch. 4

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Pare, Dwayne

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PSYB57 – Chapter 4: Paying Attention Selective Attention Dichotic Listening  Participants wear headphones and hear a different stimulus in each ear o Stimulus they are instructed to pay attention to = attended channel o Stimulus they are instructed to ignore = unattended channel  To make sure they were paying attention, the participants were given a task called shadowing in which they would have to hear the speech in the attended channel and repeat it back word for word while ignoring the unattended stimulus  Shadowing performance was almost close to perfect  The participants had no idea about what was said in the unattended stimulus  Physical attributes of an unattended channel are heard even though participants seem oblivious to the unattended channel’s semantic content Some Unattended Inputs are Detected  Words with some personal performance are often noticed, even though the rest of the unattended channel is perceived only as an undifferentiated blur  Cocktail party effect = attended to only 1 conversation in a room with multiple conversations which you tune out Perceiving and the Limits on Cognitive Capacity  You somehow block processing of the inputs you’re not interested in  This proposal was central for early theories of attention, “bottleneck theories”, which suggested that you erect a filter that shields you from potential distractors  More recent evidence suggests that this filtering is rather specific and is done on a distractor-by- distractor basis  You seem able to inhibit your response to “this” distractor and “that” distractor but those efforts are of little value if some new, unexpected distractor comes along  You are also able to promote the processing of desired of stimuli Inattentional Blindness  In an experiment, participants were instructed to point their eyes at the dot in the middle of the screen and make judgments about a cross shown off to the side. The dot itself briefly changed to another shape  If the participants were not warned about the change, they never noticed the change even though it was in front of them  The failure to see the change was caused by the fact that the participants were not expecting any shapes to appear and were not in any way prepared for these changes (inattentional blindness) Conscious Perception, Unconscious Perception  There is no conscious perception without attention  In an experiment, participants were shown a series of images, containing a pair of horizontal lines and fins at the end of the lines. The task was to decide which of the two lines was longer.  For the first 3 trials, the background dots were arranged randomly. In the fourth trial, the dots were arranged in a way that they produced an illusion  The participants didn’t perceive the fins consciously, but they were influenced by the fins in a way that they followed the misconception of the illusion  This shows that attention may be needed for conscious perception but perhaps you can unconsciously detect pattern in the world even in the absence of attention Change Blindness  Change blindness = observers’ inability to detect changes in scenes they’re looking at directly  In demonstration, participants see one picture and then a second and they alternate the pictures, trying to the detect the difference  If the change involves something central to the scene, observers may need as many as a dozen alternations between the pictures before they detect the change  If the change involves some peripheral aspect of the scene, then as many as 25 alternations may be needed  In another demonstration, participants were to watch a video in which every time there was a shift in the camera angle, there was a change in the scene. When the viewers watched the video, they noticed none of the changes Early Versus Late Selection  The studies may reveal genuine limits on perception, so that participants literally don’t see these stimuli, or these studies may reveal limits on memory, so that people do see the stimulus but immediately forget what they’ve seen  According to the early selection hypothesis, the attended input is identified and privileged from the start, so that the unattended input receives little analysis  According to the late selection hypothesis, all inputs receive relatively complete analysis, and the selection is done after all of this analysis is finished  Each hypothesis captures a part of the truth  If the input is particularly complex, then the processing of this input will demand a lot of effort and a lot of cognitive resources. Little effort will be left over for other stimuli, with the consequence that the other stimuli receive is less processing, leading to a data pattern consistent with early selection  If the attended input is simple, processing will demand few resources, leaving more available for the unattended inputs. The unattended inputs will probably receive more analysis and show a late pattern of selection Selective Priming  Looking directly at an input is not enough to allow conscious perception  Priming is produced by your visual experience and can also come from your expectations of what the stimulus will be  People can literally prepare themselves for perceiving by priming the suitable detectors  We don’t notice any changes in the inattentional blindness because we don’t expect any stimulus to appear, so they have no reason to prepare for any stimulus. Thus, when the stimulus is presented, it falls on unprepared (unprimed) detectors. The detectors don’t respond to the stimulus and we end up not perceiving it  In selective listening, we don’t want to hear the distractor so devoting resources to the distractor would be a waste of resources. Therefore, the detectors needed for the distractor receive no resources and thus are unprimed, making it more difficult to hear the distractor Two Types of Priming  Perception requires primed detectors and this priming can come from 2 different sources  Sometimes priming is a simple matter of the stimuli you’ve encountered in the past o This takes no effort on your part and requires no resources  You can deliberately prime detectors for inputs you think are upcoming so that you’re ready for those inputs you think are upcoming, so that you’re ready for those inputs when they arrive  This priming is under your control and dependent on your expectations  The detectors for these inputs remain unprimed  In a study, a pair of letters were shown on a computer screen , and participants had to decide whether the letters were the same or different  Before each pair, the participants saw a warning signal. 3 conditions: o Neutral – warning signal was a + sign; notified participants that stimuli is about to arrive o Primed – warning signal was a letter and matched the signal to come o Misled – warning signal was a letter but different from the stimuli to come  The study recorded the response times in each condition. Accuracy rates were high in each condition but the speed of response changed from condition to condition  The experiment was done in 2 different versions o Warning signal was excellent predictor of the upcoming stimuli (high validity)  Faster response times are expected in this version. Participants had good reason to trust the primes and good reason to generate an expectation based on the prime (repetition priming)  Produce a warm-up effect and an expectation effect o Warning signal was poor predictor of the upcoming stimuli (low validity)  In this version, participants cannot use the prime as a basis for predicting the stimuli therefore the prime should not lead to any specific expectations  Produces only the warm-up effect  Response times were faster in the primed condition than in the neutral condition.  Priming is observed even in the absence of expectations. Priming seems stimulus-based  Performance in the misled condition was the same as in the neutral condition  Priming one detector influences the functioning of that specific detector but neither helps nr hinders the other detectors Explaining the Costs and Benefits  2 types of primes o Stimulus-based = produced by presentation of priming stimulus with no role for expectations 
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