Lecture 3 - Early and late selection

Question 1

When does selection occur?

Answer 1

• Broadbent, Cherry & Treisman argued for early selection

Question 1

What is the capacity of the attentional filter?

Answer 1

• 3-4 items
• p’s can accurately track up to 5 objects
• there is a debate over the no. of locations that can be attended:
  -> some argue for multiple loci (up to 4)
  -> others argue for a single, invisible locus of attention

Question 2

Evidence for early selection?

Answer 2

• Broadbent argued that unfiltered stimuli are not processed at all
• shadowing - very poor recall for information presented to unattended ear
• there is some evidence that unfiltered stimuli can be processed as occasionally words from the unattended ear are reported
• Treisman argued that irrelevant information can pass through the filter if capacity is not filled by relevant information

Question 3

What are ERP’s (event related potentials)?

Answer 3

• an electrical signal associated with a mental event
• studies of ERP’s are consistent with early selection

Question 4

Sensory processing?

Answer 4

• attention produces signal enhancement in visual cortex
• attention enhances spatial resolution
• attended locations have higher perceived contrast
• evidence from neurophysiology:
  -> attention modulates the responses of early visual areas such as v1,v2,v4 and v5
  -> attention lowers phosphene thresholds in visual cortex

Question 5

Late selection - Deutsch & Deutsch?

Answer 5

• proposed that filtering occurred after perceptual processing
• selection based on which items are consistent with the observers goals

Question 6

Evidence for late selection Eriksen & Eriksen?

Answer 6

• Flanker interference effects
• present p’s with chevrons
• p’s have to identify direction of central chevrons (either left or right)
• reaction times faster and fewer errors in congruent condition

Question 7

Electrophysiology - Hillyard et al?

Answer 7

• electrophysical studies of auditory attention
• participants attend to 1 ear ignore the other
• detect occasional probe stimuli in a stream of ‘standards’ (non target sounds)
• suggest attention can modulate both early and late processing

Question 8

Perceptual load theory?

Answer 8

• proposed by Lavie
• assumptions:
  -> attentional resources are limited in capacity
  -> task-relevant stimuli are processed before task-irrelevant stimuli
  -> All of the attentional resources must be used
• in low load tasks all items in a display pass through the filter and get analysed, irrelevant items interfere with processing of relevant ones
• in high load tasks only task relevant items pass through filter + irrelevant items cannot interfere with processing of relevant stimuli
• in this model, selection occurs both in the early stages of processing (high-load condition) and in the late stages (low-load condition)