PSYB57H3 Chapter Notes - Chapter 4: Cocktail Party, Change Blindness, Briey
Chapter 4: Paying Attention
Selective Attention
•William James
Dichotic Listening
•Dichotic listening: participants wore headphones, and heard one input in the left ear and a
different input in the right ear
•Attended channel: the input participant is to pay attention to, opposing to the unattended
channel
•Shadowing: repeating what they hear from attended channel; to make sure they are listening.
Initially difficult but gets easier
•Participant’s shadowing performance is generally close to perfect
•Only 4 out of 30 participants detected the character of the unattended channel in a study,
otherwise people have no idea what it was
•Visual: participants missed the gorilla walk by in the middle of the ball game
•They can however, tell whether there was speech, music, or silence: physical attributes are
heard, but semantic attributes are not
Some Unattended Inputs Are Detected
•Your own name
•Mentioning a movie you just saw
•Your favourite restaurant
•Words with some personal importance can catch your attention
•Cocktail party effect: you are engaged in a conversation, not paying attention to the
conversation going on near you; but when your close friend’s name is mentioned in the other
conversation you stop paying attention to your own conversation and listen to the other one
Perceiving and the Limits on Cognitive Capacity
•Perhaps you somehow block processing of the inputs you’re not interested in
•Bottleneck theories: you erect a filter that shields you from potential distractors
•Not only do you block the processing of distractors, but you are also able to promote the
processing of desired stimuli
Inattentional Blindness
•Being absorbed in thoughts about other matters and becoming blind to an otherwise salient
stimulus
•Mack and Rock
•Chabris and Simon say that perception requires work, it’s not just about having stimuli in front
of your eyes
Conscious Perception, Unconscious Perception
•Mack and Rock argue that there is no conscious perception without attention
•Attention may be needed for conscious perception, however you can unconsciously detect
and be influenced by patterns 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
Early Versus Late Selection
•Is the limit on perception, so that participants don’t see the stimuli, or memory, so they see it
but don’t remember it?
•Early selection hypothesis: the attended input is identified and privileged from the start, so
that the unattended input receives little analysis and so is not perceived
•Late selection hypothesis: all inputs receive relatively complete analysis, and the selection
is done after all of this analysis is finished. Perhaps the selection is done just before the
stimulus reach consciousness, and so we become aware only of the attended input. Or
perhaps the selection is done later still, so that all the inputs make it briefly into
consciousness, but then the selection is done so only the attended channel is remembered
•Both of these hypotheses capture part of the truth
•Some data shows that attended inputs and unattended inputs are distinguishable 80 ms after
stimulus presentation, favouring late selection
•Recordings from neurons in Area V4 of the visual cortex show that these neurons are more
responsive to attended inputs than unattended inputs, favouring early selection
•The answer? If the attended input is complicated, more resources are required and so early
selection is used. If the attended input is simple, less resources are required and more room is
available for processing the unattended input
Selective Priming
•Priming can come from what you’ve seen or used shortly before, or even from what your
expectations were
•People can literally prepare themselves for perceiving by priming the suitable detectors
•Why don’t participants notice the shapes in inattentional blindness studies? The answer lies in
the facts that they don’t expect any stimulus to appear, so they have no reason to prepare for
any stimulus. The stimulus then falls on unprepared detectors
Two Types of Priming
•Perception requires primed detectors
•Sometimes the priming is a simple matter of the stimuli you’ve encountered, taking no effort
on your part and no resources
•Another type of priming is under your control, and dependent on your expectations. You can
control this by deliberately priming detectors for inputs you think will be upcoming
•Study by Posner and Snyder
•In the neutral condition, the warning signal was a plus sign and notified participants that the
stimuli were about to arrive but provided no other information
•In the primed condition, the warning signal was itself a letter and actually matched the
stimulus to come, so someone might see G before GG
•In the misled condition, the warning sign was misleading - a different letter from the stimulus
•If the warning signal was an excellent predictor of the upcoming stimuli, 80%, it is a high-
validity prime, as opposed to low-validity.
Explaining the Costs and Benefits
•Expectation-based priming takes longer to kick in than stimulus-based priming--maybe
because you need a moment to form an expectation and a bit longer to activate the detectors.
Thus, stimulus-based priming can be observed immediately after the prime; priming based on
expectations takes about half a second to develop
Document Summary
Change blindness: change blindness: observers" inability to detect changes in scenes they"re looking at directly. Perhaps the selection is done just before the stimulus reach consciousness, and so we become aware only of the attended input. If the attended input is complicated, more resources are required and so early selection is used. If the attended input is simple, less resources are required and more room is available for processing the unattended input. The answer lies in the facts that they don"t expect any stimulus to appear, so they have no reason to prepare for any stimulus. Explaining the costs and bene ts: expectation-based priming takes longer to kick in than stimulus-based priming--maybe because you need a moment to form an expectation and a bit longer to activate the detectors. Priming the wrong detectors takes something away from the other detectors.
