targets

The psychological and neural mechanisms of attention
Detect the change
Continuity Errors in Motion Pictures
• Cuts within filmed scenes often produce large spatiotemporal discontinuities introduced during the interleaved editing of multiple takes
• Because attention is typically devoted to the actors’ faces or other salient events, peripheral continuity errors are usually missed.
Continuity: In the Mace Windu/Palpatine fight scene, the glass window is shattered after being hit by a lightsaber. However, while Palpatine is talking to Anakin after the fight, you can still see Anakin's reflection in the space where the glass was.
Attention selects one modality over another
Cell phone use while driving
What is attention?
• Selective
– “Everyone knows what attention is. It is the taking possession by the mind in clear and vivid form, of one out of what seem several simultaneously possible objects or trains of thought… It implies withdrawal from some things in order to deal effectively with others.”
­William James (1890)
• Capacity limited
Four Domains of Perceptual Selectivity
• Space: the “spotlight of attention”
• Features: color, motion, orientation, etc.
• Objects: overlap, occlusion, transparency, grouping, segmentation, etc.
• Sensory Modalities: driving with a mobile phone
– Vision
– Audition
– Touch
Three Modes of Attentional Control
• Stimulus­driven, bottom­up, involuntary, automatic
• Goal­driven, top­down, voluntary, deliberate
• Hybrid: contingent attentional capture (a deliberate top­down attentional set evokes an “involuntary” redeployment of attention)
Early studies of attention­Dichotic listening
• Cherry (1953) shadowing experiments: spatial separation supports selective listening, and little semantic analysis of ignored information is reportable (but “low­level” changes, such as a change in the gender of the speaker, are detected)
• Moray (1959) found that the listener detected their own name in the unattended channel fairly often (but not always). This could mean
– All ignored information is fully represented at a semantic level and then discarded (“late selection”)
– An early filter is set that permits pertinent information (e.g., one’s own name)
to pass (“early selection”)
Early vs. late selection
•
•
•
•
Early: selection based on basic physical properties, e.g., color, location, frequency…
Late: all stimuli are processed, selection occurs on high level representations.
Early attenuation model (Treisman).
Multi­level selection model.
Capacity limitation in the temporal domain
• Attentional blink (show demo)
Overt vs. covert visual attention
• Overt: with eye movements
• Covert: without eye movements
“It is a curious fact, by the way, that the observer may be gazing steadily at the two pinholes and holding them in exact coincidence, and yet at the same time he can concentrate his attention on any part of the dark field he likes, so that when the spark comes, he will get an impression about objects in that particular region only. In this experiment the attention is entirely independent of the position and accommodation of the eyes, or indeed, of any known variations in or on the organ of vision. Thus it is possible, simply by a conscious and voluntary effort, to focus the attention on some definite spot in an absolutely dark and featureless field. In the development of a theory of the attention, this is one of the most striking experiments that can be made.”
(Helmholtz, 1867, Physiological Optics, Vol, 3, p. 455. Thoemmes Press Ed.)
Visual spatial attention
• Endogenous attention: voluntary deployment of attention according to goals
• Endogenous cueing paradigm
– Cue precedes target
– Valid most of the time
Visual spatial attention
• Exogenous attention: involuntary shifts of attention to salient objects/events.
• Exogenous cueing
– Cue can be uninformative
– Effect is transient
– At longer cue­to­target interval, starts to show inhibition­of­
return (IOR)
Visual search
Treisman & Gelade (1980)
• Target is easy to find among distracters that do not share the critical target feature (pop­out search)
• Target is hard to find among distracters that share features with target (conjunction search) Search function
• Pop­out search­­flat slope
• Conjunction search­­slope indicates speed of serial scanning of items
– target absent slope is ~ twice of that target present slope.
– Self­terminating for present, exhaustive for absent
Feature integration theory
• Separate feature maps, parallel processing
• Preattentive (parallel) processing is sufficient for feature search (pop­out)
• Focal attention for conjunction search to conjoint different features (binding)
Domains of selection: Objects
Domains of selection: Objects
Duncan (1984)
•Breifly flashed stimulus consisting of two objects: box and line
•Each object has two attributes:
•Box is tall or short and has a gap on the left or right
•line is solid or dashed and tilted left or right
•Report two atributes: both on one object or one on each object
Performance was worse when one attribute on each object had to be reported, suggesting that all the attributes of an attended object are apprehended as a whole: an instance of “object­based selection.”
Attentional systems in the brain
Questions about visual attention:
• How does attention modulate perceptual representations—that is, what are the effects of attention?
• How is attention controlled—that is, what is the source of attentional control signals?
Some targets of attentional modulation in vision
hMT+ (motion)
V1­V4 (early vision
)
Superior temporal gyrus (early audition)
Fusiform gyrus (faces/houses)
V4 receptive field
Instructio
nal fixation pt
Attention out of rf
Attention into rf
Respond to red
Motter (1994). J. Neuroscience, 14, 2190­2199.
V4
Switch attention into RF
Switch attention out of RF
Motter (1994). J. Neuroscience, 14, 2190­2199.
Spatial Attention Task
Instruction Trials
Test Trials
Fixation
Point
Cue
Box
Non
Target
Distractor
Receptive
Field
Target
Reynolds, Chelazzi and Desimone, 1999, J. Neurosci.
Spikes per second
Preferred,
Att Away
V4
80
60
40
20
0
0
100
200
ms. after stimulus onset
300
Poor,
Att Away
Preferred,
Att Away
Spikes per second
Pair,
Att Away
V4
80
60
40
20
0
0
100
200
ms. after stimulus onset
300
Poor,
Att Away
Preferred,
Att Away
Spikes per second
Pair,
Att Away
V4
80
Pair,
Att
Preferred
60
40
Attention
20
0
0
100
200
ms. after stimulus onset
300
Poor,
Att Away
Preferred,
Att Away
Spikes per second
Pair,
Att Away
V4
80
Pair,
Att
Preferred
60
40
Attention
20
0
0
100
200
ms. after stimulus onset
300
Poor,
Att Away
Critical Points:
1. The representation of visual objects is distributed throughout the cortical hierarchy; local high­resolution information is carried by neurons at early levels, while abstract global information about identity, category, meaning, and value are carried at later levels.
2. Most neurons have multiple objects within their receptive fields. Selection must occur in order that a given neuron ‘knows’ which of the objects in its receptive field it is to represent. Some sources of attentional control
Frontal eye fields (FEF)
Superior parietal lobule (SPL) and precuneus
Intraparietal sulcus (IPS)