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PSYB57H3 (369)
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Chapter 4

PSYB57 – Chapter 4 Notes.docx

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University of Toronto Scarborough
Dwayne Pare

PSYB57 – Chapter 4 Notes  The stimulus you’re attending to is only one of many that are available to you, and this fact invites two crucial observations o First, it seems clear that you could choose to pay attention to any of the things just mentioned, and if you did, you would be virtually oblivious to the other things on the list o Second, there seems to be one thing you cannot do: you cannot pay attention to all of these things at once  Many early studies of attention employed a task called shadowing o In this task, participants hear a tape recording of someone speaking and must echo this speech back, word for word, while they are listening to it  In most experiments, the message to be shadowed, the attended channel, is presented through stereo headphones, so that participants hear the attended channel through, say, the right earphone o A different message – the unattended channel – is presented in the left earphone, and participants are instructed simply to ignore this message; this overall step if referred to as dichotic listening o Can’t tell what unattended channel is  In selective listening experiments, people easily and accurately report whether the unattended channel contained human speech, musical instruments, or silence  It seems then that physical attributes of the unattended channel are heard, even though participants seem oblivious to the unattended channel’s semantic content  Words with some personal importance will be noticed (ex: your name in unattended channel) o Cocktail party effect  Two broad options for how we might think about attention o One option focuses on what we do with the unattended input  Proposal = somehow we block processing of the inputs we’re not interested in, much as sentry blocks the path of unwanted guests but simply stands back and allows legitimate guests to pass – we erect a filter that shields us from potential distractors; desired information (the attended channel) is not filtered out and so goes on to receive further processing o Not only do we block the processing or distractors, but we are also able to promote the processing of desired stimuli  The failure to see, caused by inattention, has been dubbed inattentional blindness (study done on + and shapes after is disappears and if anything changed; participants failed to notice change)  Our normal ability to see what’s around us, and to make use of what we see, is dramatically diminished in the absence of attention  Mack and Rock argue that there is no conscious perception without attention  Change blindness: observers’ inability to detect changes in scenes they are looking directly at  If the change involves some peripheral aspect of the scene, then as man as 25 alternations may be required  There are two ways we may think about these results (as noted from before): these 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 stimuli but immediately forget what they have just seen  Early Selection hypothesis: the attended input is identified and privileged from the start, so that the unattended input receives little analysis (and so it is never perceived)  Late Selection hypothesis: all inputs receive relatively complete analysis; but it is only the attended input that reaches consciousness, or (as a related idea) it is only the attended input that is remembered  Both capture part of the truth ^  Recording from neurons in Area V4 of the visual cortex shows that the neurons are more responsive to attended inputs than to unattended ones, almost as if attention made the light areas seem brighter and dim areas seem darker  These results argue that attention doesn’t just change what we remember or what we’re aware of; attention can also literally change what we perceive  If the input is particularly complex, then the processing of this input will demand a lot of effort and a lot of cognitive resources; in this case, little effort will be left over for other stimuli, with the consequence that the other stimuli receive les processing, leading to a data pattern consistent with early selection o If the attended input is relatively simple, processing will demand few resources, leaving more available for the unattended inputs; here the unattended inputs will probably receive more analysis, and so we’ll see the pattern of late selection  In some cases, priming is produced by one’s visual experience – specifically whether each detector has been used recently or frequently in the past; but also, priming can come from another source: your expectations about what the stimulus will be  The idea, in short, is that resources are needed to prime detectors, and that those resources are in limited supply  Response Times were reliably faster in the primed condition than in the neutral condition; apparently then, detectors can be primed by mere exposure to a stimulus  Performance in the misled condition was the same as performance in the neutral condition; priming the “wrong” detector it seems, takes nothing away from the other detectors – including the detectors actually needed for that trial  The combination of warm-up and expectations (high-validity prime), leads to faster responses than warm-up alone  Misleading participants actually hurt performance; with high-validity primes, responses in the misled condition were slower than responses in the neutral condition  Data shows there are two types of primes o One type is stimulus-based – produced merely by presentation of the priming stimulus, with no role for expectations o The other type of priming is expectation-based, and is created only when the participant believes the prime allows a prediction of what’s to come  Expectation-based priming is larger in magnitude, leading to a greater benefit in the RT data  It also takes longer to kick in: stimulus-based priming can be observed immediately after the prime; priming based on expectations takes roughly a half second to develop  The two types of priming can also be distinguished in terms of their “cost” o Stimulus-based priming appears to be “free”(cost), and so we can prime one detector without taking anything away from the other detectors (low validity condition, in the fact that the misled trials lead to responses just as fast as those in the neutral trials) o Expectation-based priming does have a cost (as we see in the high- validity condition) – priming the wrong detector does take something away from the other detectors, and so participants are worse off when they’re misled than when they received no prime at all  Expectation-based priming, by virtue of revealing costs when misled, reveals th
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