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
x x x
o o o
x o o
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…”
“Four score
and seven
years
ago…”
“It was the
best of
times, it was
the worst of
times…”
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