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Lecture 6

Class 3, Lecture 6, Chapter 4- Paying Attention.docx

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Carolyn Ensley

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Class 3, Lecture 6, Chapter 4: Paying Attention Selective Attention  Other studies of attention focus on a phenomenon known as change blindness, the inability of observers to detect changes in scenes they are looking directly at.  See if you can detect the differences between the following pairs of pictures:  Similar effects of change blindness occur when people fail to notice continuity errors in films.  In a particularly striking example, participants failed to notice when the person asking them for directions changed identity (following a brief interruption by two people carrying a door).  Early studies of attention focused on when the perceiver selects the desired input.  According to the early-selection hypothesis, the unattended input receives little to no analysis o based on  According to the late-selection hypothesis, all input receives analysis but only the attended input reaches consciousness or is remembered. o Things with meaning are picked up indicating that it has to be processed with meaning before processing on it is stopped.  Both the early- and late-selection hypotheses capture part of the truth. o For instance, the study discussed earlier showing that unattended stimuli have effects on perception seems to be a case of late selection.  The idea that we process things up to a level of meaning and pay attention to what we select up to o However, the electrical activity of the brain for attended versus unattended inputs differs within 70 ms of stimulus presentation, suggesting early selection.  Selection is occurring with 70 ms, brain activity is the same for unattended and attended for up to 70 ms. After 70ms, there is a difference in processing between the two.  It is only with those things that are high in meaning to us are recognized early/quickly enough that they get to that level of meaning before this 70ms level of change.  An experiment by Posner and Snyder (1975) illustrates that there are two kinds of priming related to attention. o One kind of priming is stimulus-based, the other is expectation-based.  Both speed up response times, top down and bottom up can produce priming  For this type of study, the dependent variable is the response time to make a decision about the stimuli. o Showed that priming can be turned “off” and “on”  Posner and Snyder (1975) found in the low-validity condition (the condition where your prime wasn’t a good predictor of the next stimulus) that the primed condition was faster than neutral. o This demonstrates an effect of repetition priming; the receptors were “warmed up.”  There was no expectation priming  no expectation  But, the misled condition was not any slower than neutral. o Warming up the “wrong” detector does not take activation away from the correct one. o People learned to ignore that prime and not be affected by it, or were not using it to their advantage  Posner and Snyder (1975) found in the high-validity condition that the primed condition was much faster than neutral. o This demonstrates an additional effect of expectation in addition to repetition priming. o Faster then the low validity because the individual was able to take the stimulus cue and the meaning cue  Further, the misled condition was slower than the neutral condition. o Expectation is limited in capacity; the “wrong” expectation interferes with activating the correct detectors.  When they were expecting that prime to tell them what is coming next, their response time was slower. Have the least advantage of priming  We only use expectation when it is valid  Studies of spatial attention examine the ability to focus on a particular position in space and to be prepared for stimuli appearing in that position.  For example, when detecting a stimulus on the right or left side of the screen, participants benefit if an arrow provides a cue indicating on which side the stimulus is about to appear (Posner et al., 1980). o They do this with eye trackers going, even when the eyes are not moving are still able to move our attention  Note that directing spatial attention is different than moving the eyes.  Spatial attention is sometimes thought of as a “searchlight.”  We can move this searchlight in space, as well as adjust the size of the “beam.” o  Do we attend to positions in space or to objects?  Evidence from unilateral neglect syndrome, caused by damage to the right parietal lobe, could be argued to support a space-based view. These individuals cannot attend to the left side of space. o Damage to the right affecting the left visual field  contralateral processing  However, some experiments suggest that the deficit is also object-based.  Unilateral-neglect patients attended to the red circle, initially presented on the right, even after it rotated to the left side of the object. o In the beginning they could not attend to the circle in the left visual field. o Only able to pay attention to the left visual field as long as they followed t
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