PSYC 330 Chapter Notes - Chapter 5: Zoom Lens, Iconic Memory, Electric Spark
4 Jun 2018
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CH5 Orienting of Attention
Introduction
Overt & covert orienting
- Orienting response: response that animals make (adjustment of animal’s position)
toward stimuli that captures their attention
■ When confronted with a novel stimulus → strong orienting response towards it
■ When the same stimulus is repeatedly presented → animal will gradually
habituate to it → orienting response will progressively weaken
- The habituation → gradual
decrease in cortical arousal
caused by reticular activating
system (RAS)
- The RAS arouses the cortex by
a pathway that projects to the
thalamus
- 1949: electrical stimulation of
the RAS of cats produced
arousal and orienting responses
1. Overt orienting: shifts of attention associated with detectable body movements (eye/
head/ body movements)
2. Covert orienting: shifts of attention not associated with any directly observable body
movements
Why not just move your eyes? (Overt)
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- Might not be worth moving your eyes → as it’s time consuming (4/second)
- Covert attention is much faster than overt orienting
- When we move our eyes, vision is temporarily suspended
- Don’t move your eyes too much while driving
Helmholtz’s study of attention orienting
- First to study attention shifts in a systematic manner (Hermann von Helmholtz, 1880s)
- Had a gift for improvisation to build optical models, using household materials,
eg children’s building blocks, candle wax
- Demonstrated our capacity to (voluntarily and selectively) concentrate attention on a
different portion of the visual field than where our eyes are pointing (attentional focal
point can be shifted independently of ocular fixation)
- During experiments, subjects is always
looking at the fixation point
- Decide which part of the darkened
display he wanted to focus on →
concentrate his attention at that
location before spark illumination →
those letters in the area where
attention had been concentrated were
most identifiable (A)
- However, letters in the vicinity of the
ocular fixation point were difficult to
identify (B)
- Covertly oriented his attention to
location within a stimulus display while overtly maintaining position of eyes and gaze
toward central fixation
Location Cueing (covert orienting)
Sperling’s auditory cue experiment
- Different tone (high, med, low) =
different location to attend to (top,
middle, bottom)
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- Studying iconic memory
- Cues comes after stimulus
Posner task (visual cue)
- Developed a location cueing method
■ Central fixation point that subjects must continually direct their eyes toward
throughout each experimental trial
■ Visually presented target item to
which subjects must respond
■ Location cue that is presented
immediately before the target’s
appearance
- The cue indicates, with a
certain probability, the
impending target’s location
- Therefore directing attention
toward the expected target
location prior to its onset
- Cue-target onset asynchrony (CTOA): delay between the cue and the target
■ Subjects are required to make a simple detection response (eg pressing a button)
■ If CTOA is less than 200ms, subjects will not have enough time to make an eye
movement to the cued location before the target appears
- Time required to program and execute a regular saccadic eye movement is
about 220 ms
■ To ensure that attention was shifted independently of eye
fixation
- Helmholtz illuminated his stimulus displays with an
electric spark so that they were visible only briefly
and there was not enough for eye movements to be
made
● Cost-benefit analysis of cueing effects
- Posner, 1978, Experiment 3
- Subjects were required to detect the onset of a target that could occur at one of two
possible locations 6.9 degrees to the left/ right of the centre
- 80% of the trials: target appeared at the cued location
- 20% of the trials: target appeared somewhere else
■ Valid-cue trials: target appears at the cued location
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