Stages of Selection

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 meaning of words) in unattended channel shouldn’t be processed for meaning

Stages of Selection

• Shadowing Task: ignore one input, repeat back the other

• Subjects are largely unaware of unshadowed message but…

• Certain words such as their name distract them!?

• Why is this puzzling?

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

Orienting Attention

Control of Attention

• Major Distinctions:

Voluntary Reflexive

Control of Attention

• Major Distinctions:

Voluntary Reflexive

Overt Covert

Voluntary Orienting

• Attention can be oriented covertly – a commonly used metaphor is “the spotlight of attention”

Orienting Attention

• Posner Cue - Target Paradigm:

Subject presses a button as soon as x appears

Orienting Attention

• Posner Cue - Target Paradigm:

Orienting Attention

• Posner Cue - Target Paradigm:

Orienting Attention

• Posner Cue - Target Paradigm:

Orienting Attention

• Posner Cue - Target Paradigm:

X

Orienting Attention

• Posner Cue - Target Paradigm:

Orienting Attention

• Posner Cue - Target Paradigm:

That was a validly cued trial because the x appeared in the box that flashed

Orienting Attention

• Posner Cue - Target Paradigm:

Orienting Attention

• Posner Cue - Target Paradigm:

Orienting Attention

• Posner Cue - Target Paradigm:

Orienting Attention

• Posner Cue - Target Paradigm:

X

Orienting Attention

• Posner Cue - Target Paradigm:

Orienting Attention

• Posner Cue - Target Paradigm:

That was an invalidly cued trial because the x appeared in the box that didn’t flash

Paradigms Used To Study Attention

• Posner Cue - Target Paradigm:

Attention Effect = Valid RT - Invalid RT

Voluntary Orienting

• Under what circumstances would a cue lead to a voluntary shift of attention?

Voluntary Orienting

• Under what circumstances would a cue lead to a voluntary shift of attention?– Informative cue– Validity = greater than 50%

Voluntary Orienting

• Under what circumstances would a cue lead to a voluntary shift of attention?– Informative cue– Validity = greater than 50%

• What is another way to make this paradigm a voluntary orienting paradigm?

Voluntary Orienting

• What is another way to make this paradigm a voluntary orienting paradigm?

Symbolic cues may orient attention towards another location.Stimulus cues orient attention to the stimulated location.

Symbolic Cue

Reflexive Orienting

• Attention can be automatically “summoned” to a location at which an important event has occurred:

Reflexive Orienting

• Attention can be automatically “summoned” to a location at which an important event has occurred:– Loud noise– Motion– New Object

• We call this attentional capture

Transients

Reflexive Orienting

• The Posner cueing paradigm (with blinking boxes) confounds reflexive and voluntary orienting

… in what way?

Reflexive Orienting

• The Posner cueing paradigm (with blinking boxes) confounds reflexive and voluntary orienting

• How could we change the Posner cueing paradigm to make it asses only reflexive orienting?

Reflexive Orienting

• The Posner cueing paradigm (with blinking boxes) confounds reflexive and voluntary orienting

• How could we change the Posner cueing paradigm to make it asses only reflexive orienting?

• Make validity 50% (non-informative cue)

Reflexive Orienting

• The Posner cueing paradigm (with blinking boxes) confounds reflexive and voluntary orienting

• How could we change the Posner cueing paradigm to make it asses only reflexive orienting?

• Make validity 50% (non-informative cue)

• Viewers are still faster and more accurate!

Reflexive Orienting

• Can symbolic cues be reflexive?

Almost never but …

Reflexive Orienting

• Can symbolic cues be reflexive?

Reflexive orienting to direction of eye gaze

Reflexive Orienting

• Potential cues for Reflexive Orienting– Loud noise– Motion– New Object

• New Objects are powerful attention grabbers!

Transients

New Objects Capture Attention

IS THERE AN “H”?

Initial scene viewed for several hundred ms

Yantis & Jonides (1990): New-Object Paradigm

New Objects Capture Attention

New scene: search for target letter

IS THERE AN “H”?

Yantis & Jonides (1990): New-Object Paradigm

H may be revealed from an 8 or may appear as a new object

Reflexive Orienting

• Steven Yantis and colleagues– Result:

Reflexive Orienting

• Steven Yantis and colleagues– Result:

Targets are found faster when they are “new objects” than when they are revealed from “old” objects

Reflexive Orienting

• Steven Yantis and colleagues– Interpretation:

The visual system prioritizes in dealing with visual objects - relatively recent objects are “flagged” while older objects are disregarded

Attention and Consciousness

• The attention orienting mechanism can be confused leading to something called “change blindness”

Attention and Consciousness