- Many early studies of attention employed a task called shadowing hear a tape recording of someone speaking and echo this
speech back, word for word, while they are listening to it.
o Initially challenging, but it becomes relatively easy after practice
- In most experiments, the message to be shadowed, the attended channel, is presented through stereo headphones on the right
side. A different message—the unattended channel—is presented in the left earphone, and participants are instructed to ignore
o This overall setup is referred to as dichotic listening.
o In most cases, participants cannot even tell if the unattended channeled message was coherent or not. – However could
indicate if it is speech, music, or silence.
o Recently this has been done visually – asked to pay attention to game of basketball, and you don’t notice the
Some Unattended Inputs Are Detected
- In one study, people were asked to shadow one passage while ignoring a second passage.
o If their own name was mentioned, then most participants heard it.
- Cocktail party effect - There you are at a party, engaged in conversation. Many other conversations are taking place, but you
―tune them out.‖ You are aware that other people are talking, but you don’t have a clue what they’re saying.
Perceiving and the Limits on Cognitive Capacity
- Earlier theories said that we erect a filter that shields us from potential distractors (filter on desired info – attended channel).
- When a new distracted is brought in, we need to adapt to that additionally – we don’t adapt automatically.
- We don’t only block undesired info, we promote desired stimuli.
- In a study, a ―+‖ was put up on a computer screen and participants had to look for differences. There were 4 trials. On the 4 th
trial, a new shape appeared quickly after the +. 89% of participants did not notice this.
o In this case, the ―+‖ was referred to as the fixation target.
o Didn’t notice that the fixation target changed.
- Why did this happen?
o Some researchers have proposed that the participants in this experiment did see the target shapes but, a moment later,
couldn’t remember what they had just seen.
o Mack and Rock said the participants were not expecting any shapes to appear and were not in any way prepared for
these shapes… the participants literally failed to see the shapes, even though they were staring straight at them.
Conscious Perception, Unconscious Perception
- Mack and Rock argue there is no conscious perception without attention.
- Were judging about the line lengths… they were asked ―which line was longer, top or bottom?‖
- They didn’t notice that there were fins on the lines.
- Observers’ inability to detect changes in scenes they are looking directly at.
- For example, in one experiment participants were watching a video of women talking. When looking at one woman, the plates on
the table were white, however, with the other woman they were magically red.
- 2 pictures of a beach… the middle umbrella is changed a little bit.
- Picture of stairs… pictures of stairs and windows – large window changes to small window.
- Picture of food market… the colour of oranges goes from yellow to orange.
- We’re better at this task when they’re in the center and not the peripheral.
- At a university, people come and get a paper to sign, after they sign it… then the guy ducks down, and another guy is replaced.
Different shirt, looks totally different. But 75% of people didn’t see the change.
Early Versus Late Selection
- According to the early selection hypothesis, the attended input is identified and privileged from the start, so that the unattended
input receives little analysis (and so is never perceived). Doesn’t get in our heads.
- According to the late selection hypothesis, however, 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.
- Priming can come from your expectations about what the stimulus will be. - People can literally prepare themselves for perceiving by priming the suitable detectors – priming isn’t necessarily free… uses
- Why don’t participants notice the shapes in the inattentional blindness studies?
o It may be that they don’t expect any stimulus, so they have no reason to prepare for any stimulus.
o As a result, the stimulus, when it’s presented, falls on unprepared (thus, unresponsive) detectors.
- People notice their names being said in the unattended stimuli because throughout our lives we’ve been primed to hear and know
Two Types of Priming
- A pair of letters was shown on a computer screen, and participants had to decide, as swiftly as they could, whether the letters
were the same or different.
o Before each pair, participants saw a warning signal…
In the neutral condition, the warning signal was a plus sign (―+‖).
In a different condition, the warning signal was itself a letter (―C‖ for ―CC‖).
In a third condition, the warning signal was again a letter, but it was a letter different from the stimuli to come
(―F‖ for ―CC‖) – misleading.
o Low validity – creates a situation for stimulus-based priming (no expectation)
o High validity – expecting the same letter to come up… lower reaction time (mostly primed type –―C‖ for ―CC‖)
Explaining the Costs and Benefits
- Type 1 of priming: stimulus/repetition-based—produced merely by presentation of the priming stimulus, with no role for
o If you have experience with something, then you need less input to get it to fire.
- Type 2: expectation-based, and is created only when the participant believes the prime allows a prediction of what’s to come.
o More conceptional
o Getting prepared for one target seems to make people less prepared for other targets.
o “Limited budget‖ You can spend more on ice cream if you wish, but if you do, you’ll have that much less to spend
on other foods. Limited-capacity system.
- Selective attention - perceiving involves some work, and this work requires some limited mental resources. That is why you
can’t listen to two messages at the same time; doing so would demand more resources than you have.
Chronometric Studies and Spatial Attention
- Spatial attention—our ability to focus on a particular position in space, and thus to be better prepared for any stimulus that
appears in that position.