Selective Attention

A tale of bottlenecks and basketballs

Two Distinct Processes

• There are two processes which get bundled into our idea of attention:– orienting - shifting attention (usually in space, but also to non-spatial

features such as pitch)– selection - what attention does to perception

• These are often confused and used interchangeably

• We’ll switch back and forth between the two, but we’ll try to keep them separate

• First: the consequences of selection

Information Theory:

• ~1950’s: Psychologists began to think of the human perceptual mechanisms as “information processors”

Information Theory:

• ~1950’s: Psychologists began to think of the human perceptual mechanisms as “information processors”

• Began asking questions such as “how much information can the human mind handle at once?”

Information Theory

• Donald Broadbent - earliest systematic investigations of selective attention

Information Theory

• Donald Broadbent - earliest systematic investigations of selective attention

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Information Theory

• Donald Broadbent - earliest systematic investigations of selective attention

Information Theory

• Donald Broadbent - earliest systematic investigations of selective attention

– when simultaneous questions were asked, subject performed poorly on all questions

Information Theory

• Donald Broadbent - earliest systematic investigations of selective attention

•First principle of human information processing: capacity is limited

Information Theory

• Donald Broadbent - earliest systematic investigations of selective attention

Information Theory

• Donald Broadbent - earliest systematic investigations of selective attention

– when simultaneous questions were asked from physically separate speakers, and subject instructed in advance which question to answer, performance was nearly perfect

Information Theory

• Donald Broadbent - earliest systematic investigations of selective attention

Second principle of human information processing: information sources can be selected

Shadowing

• Many early studies employed variations on a paradigm called “shadowing”

“Four score and seven years ago…”

“It was the best of times, it was the worst of times…”

“Four score and seven years ago…”

Shadowing

• Many early studies employed variations on a paradigm called “shadowing”– subjects could easily recall details of the shadowed passage

but not of the ignored passage

Shadowing

• Many early studies employed variations on a paradigm called “shadowing”– subjects could easily recall details of the shadowed passage

but not of the ignored passage

– led to the idea that the perceptual mechanisms involve one or more “filters” to shut out unwanted information

Stages of Selection

• Broadbent: Early Selection - a bottleneck exists early in the course of sensory processing that filters out all but the attended channel

• Alternative theory: Late Selection - the bottleneck exists not at the lowest stages, but at the highest - such as response planning, memory and consciousness

Stages of Selection

Stages of Selection

• Testing Early Selection Theory - what prediction can be made?

Stages of Selection

• Testing Early Selection Theory - what prediction can be made?

• Information (such as words) in unattended channel shouldn’t be processed for meaning

Stages of Selection

• Testing Early Selection Theory - what prediction can be made?

• Information (such as words) in unattended channel shouldn’t be processed for meaning

• Demonstrates that Early Selection Theory is not entirely correct

Stages of Selection

• Testing Early Selection Theory - what is another prediction that can be made?

Stages of Selection

• Testing Early Selection Theory - what is another prediction that can be made?

• Should be able to find differences in brain activity in primary sensory areas (A1, V1)

Stages of Selection

• Electrical activity recorded at scalp (EEG) shows differences between attended and unattended stimuli in A1 within 90 ms

Hansen & Hillyard (1980)

Stages of Selection

• Evidence exists for both early and late selection mechanisms

– One interpretation: early reduction in “sensory gain” followed by late suppression of unselected information

Next Time

• Read article by Anne Treisman