An introduction to attention
Peter König
What is attention
Everyone knows what attention is. It is
the taking possession of the mind, in
clear and vivid form, of one out of what
seem several simultaneous possible
objects or trains of thought.
Focalization, concentration of
consciousness are of its essence. It
implies withdrawal from some things in
order to deal effectively with others,
and is a condition which has a real
opposite in the confused, dazed,
scatterbrain state….
– William James (1890)
Overt attention
• Movements of the
eyes allow selective
aquisition of visual
signals.
• Other sensory organs
equally allow selective
capturing of
environmental signals.
Selection of signals by sensors
sensory organ
environmental signals
How are salient points selected?
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GIF decompressor
are needed to see this picture.
• The concept of a
saliency map
• “Where is the
action?”
• Bottom-up
approach
• But … !
Spotlight of attention
•
Helmholtz observed
that we can enhance
perception, if we focus our
attention on a location in the
visual field.
•
However, enhancing
perception in one part of the
visual field takes place at the
expense of other areas.
The shadowing task I
Condition 1: 65% correct
Condition 2: 20% correct
Shadowing task II
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old to miner select hid one a message box
from of another. Gold. We Although do several
this hundred by people focusing have our
looked attention for on it, certain they cues
have such not as found type it style.
Covert attention
A physiological substrate I
Attentional systems
Plaza Milano
Broadbend‘s filter theory
• Early selection.
• Selection is based on physical properties of the
stimulus (e.g., pitch, loudness, etc...).
• Only one input channel can
higher processing stage
be processed at a time.
• Semantic interpretation
only after selection.
• Conscious control.
• It takes time to shift attention. sensory signals
Late selection
Attended Channel: THE GIRL WAS dogs, six, beach ...
Unattended Channel: world, eight, WAITING FOR HER ...
Reported: THE GIRL WAS WAITING FOR HER ...
Popout
• Popout as pre-attentive processing.
The more popout, the later selection!?
• Can be trained!
Stroop task
red
yellow
blue
green
yellow
green
red
blue
blue
red
green
yellow
green
blue
yellow
red
But!?
Effects in early visual cortex
Effects of attention
Competing hypothesis
• early selection - Broadbent (1958) proposed that
physical characteristics of messages are used to select
one message for further processing and all others are lost
• attenuation - Treisman (1964) proposed higher processing stage
that physical characteristics are
used to select one message for
full processing and other messages are given partial processing
sensory signals
• late selection - Deutsch & Deutsch (1963) proposed
that
all messages get through, but that only one response can
be made (late selection).
The temporal domain
V4
Applications?!
What did we learn / the next time
•
•
•
•
Overt/covert attention
When: Early, middle, late …
What: Spatial … Object oriented attention
Where: Areas, -band … Single neurons,
Clinical syndromes
• How: Saliency maps … Top-down models
• Suggested readings: Kastner, Annual Review
neurosciences, 2000; JR Anderson, Chapter 3
A definition by exclusion
Awake
Inattentiveness
(drowsy, relaxed)
Ignore
Asleep
Alert
Attend
Different
sleep stages
Popout
•
•
•
•
Popout as pre-attentive processing.
The more popout, the later selection.
T among I and Y vs. T among I and Z.
Can be trained!
Covert attention
Treisman’s attenuation theory
higher processing stage
sensory signals
What did we learn?
• Types of attention
– Overt attention, covert attention
• What can we attend to
– Spatial attention, object based attention
- Physical characteristics, semantic contents
• Properties of attention
• Mechanisms of attention
• Why attention
What do we want to know?
•
•
•
•
•
Types of attention
What can we attend to
Properties of attention
Mechanisms of attention
Why attention
Selection by processing stages
higher processing stage
sensory signals
Parallel and serial search
Central peripheral cues
Early or late?
Treisman and Geffen (1967) set about to test
whether the filter was early or late in the processing
stream. They had subjects shadow a message on one
ear, and tap whenever they heard a certain word in
either ear. When the key word appeared in the
attended ear, subjects tapped 87% of the time, but
when the key word appeared in the unattended ear,
subjects tapped 8% of the time. This indicates that
early selection is occurring.
Conjunction search
Lesions
Monkey cortex
What can we attend to?
Spatially oriented attention
vs.
Object oriented attention
Popout as a pre-attentive mechanism
Change blindness
Selective
Divided
and divided
attention
attention
• Attention is studied by • In selective (focused)
presenting participants
attention tasks, people
with two or more
are instructed to respond
stimuli at the same time. to one input only.
• This is called dual-task • In divided attention
performance.
tasks, people are asked
to process and respond
to more than one input.
Divided attention
• Tracking task. Can track several targets
simultaneously.
Dilation in space and time
• Expanding dot demo.
Physiological mechanisms
• Partiel lobe lesions
• Balint‘s syndrome
• Attention is a gateway
to consciousness.
Covert attention, cortex
Details of parallel search
Problems with spotlight
Spotlight or zoom-lens
Object centered attention
Scaling tuning curves
Neuroscience <-> Psychology
what do these examples tell us about the relation between mental phenomena and physical
states of the brain?
*
unrelated ? complete independence -- too many corresponding phenomena
*
irrelevant ? somehow related, but without any serious implications -- unlikely,
because it is possible to influence percepts by affecting neurons (TMS)
*
correlated ? not independent, but possibly not more than common result from
unknown cause -- possible from the above, but perhaps not enough?
*
causal ? neuronal state determines mental state -- likely in some instances, but
applicable to all mental events? is consciousness emerging from neural activity?
if we would reach a complete understanding of all brain mechanisms, from the single
molecule to the function of extended neural networks, would we be able to comprehensively
predict mental states? A. Snyder (Centre for the Mind): Yes
Yet another definition
Attention - Attention is what enables us to process information about the world around us. We
can only be aware of things around us if we pay attention to them. We can think of attention as
a spotlight that we shine on things in the world around us to make them stand out. When
something "stands out," we notice it, bringing it into our awareness, and then process or
interpret it. Attention can change rapidly, switching from one thing to another. It can be
steered by our intentions ("top-down"), as when we look for a particular face in a crowd, or it
can be steered by features of objects in the world ("bottom-up"), as when our attention is
grabbed by a police car's flashing lights in our rearview mirror. Preattentive processes help us
decide what to pay attention to and what to filter out and ignore. Attention filters and feeds
information about the world around us into our minds