Attention Part 2

Early Selection Model (Broadbent, 1958) inputdetectionrecognition FI L T E R Only information that passed the filter received further analysis (e.g. meaning).

Late Selection Theory (Deutsch & Deutsch, Norman) inputdetectionrecognition FI L T E R

Early Attenuation Model (Treisman) inputdetectionrecognition FI L T E R

Lab: Feature Search Parallel processing of simple visual features (e.g., color).

Typical Results for “Feature Search” # of items in display Reaction Time (msec) “Yes” “No”

Conjunction Search Combination of features (e.g., red AND horizontal) Spatial arrangements of features (e.g. black above white) When targets are defined by:

Lab: Conjunction Search ‘Find the blue square’

Lab: Conjunction Search

Treisman’s Results for “Conjunction Search” # of items in display Reaction Time (msec) “Yes” “No”

Lab: Voluntary Cueing Valid Trials 70% Invalid Trials 15% Neutral Trials 15%

Voluntary Cueing Same result for short and long cue-to-target delays (short ‘green’, long ‘blue’)

Lab: Automatic Cueing Cued Trials ??% + Miscued Trials + Neutral Trials +

Automatic Cueing For short cue-to-target delay (‘green’), same result as for voluntary cueing (validly cued faster than invalidly cued) For long cue-target delays, the reverse pattern (inhibition of return) + +

Neurological Deficits in Visuo-spatial attention Hemi-spatial Neglect lesion in right temporo-parietal junction Inability to –attend to the left side of visual space, and thus to –be aware of visual stimulus in the left visual field –Represent spatial relations.

Line-bisection task

RightLeft LVFRVF

Right hemisphere Left hemisphere LVFRVF

To study the neural substrate of visuo- Spatial Attention, we need A patient group: –Hemispatial neglect A simple method: –Spatial Cueing A cognitive theory: – Posner’s three stage model

Disengage: –stop attending to what is currently being attended Move: –refocus spotlight on new location Engage: –begin attending to new stimulus

Spatial Cueing Cued Trials + Miscued Trials +

RetinaLGNV1 V4 Parietal Cortex Inferotemporal Cortex (Relay Station) (Detects Edges) (Color, Form) (Shape, Object Recognition) (Location, How to reach or act upon) Which part of the brain is the source of attention? Where does attention have its effects?

time Memory/Attention Task (fMRI / ERP)

Regions of Interest RVF LVF

Stim 1Stim 2 Single-Unit Recording “spike” = single neuron’s action potential (Macaque monkey) Signal Analysis Receptive Field

Attention Effects in Single Neuron Responses 100 msec Frequency of spikes Attended bar Unattended bar ( Robert Desimone, NIH)

RetinaLGNV1 V4 Parietal Cortex Inferotemporal Cortex (Relay Station) (Detects Edges) (Color, Form) (Shape, Object Recognition) (Location, How to reach or act upon) Attention Effects Here No Attention Effects Here

Early visual processing IS affected by selective attention. This is a challenge for a pure late selection model. BUT, it does not mean that late selection is not occurring. Conclusions from Neuroscientific Evidence:

Automatic vs. Voluntary Priming +AA Warning signal Test signal neutral (Posner & Snyder, 1975)

SKK 15% P PP SKK GGG 15% 70% “No need to think of P” Automatic Priming “think of P! yeah baby!” Automatic Priming Voluntary Priming Often misleading GGG 70% Often predictive

Difference between experimental and neutral conditions faster slower 15% primed 70% misled 70% primed 15% misled Low validity (often misled) High validity P -> P P ->G P ->P Automatic Priming; Benefit without a cost Voluntary Priming Benefit with cost

Automatic vs Voluntary priming (part 2) Neely (1977) If you see a body part as a Prime, expect a building part as a target. For example, –Body -> door some pairs were semantically related, but unexpected – body -> heart

Priming Results Blue: Expected pair – Body -> door – voluntary priming –Evolves with time Green: Related but unexpected –Body -> heart – automatic priming, followed by a cost from voluntary priming Cue-target delay (ms) Cost facilitation (ms)

Question Predict pattern of performance when: –the delay between cue and target is very short, –the cue-target delay is longer –For automatic priming –For voluntary priming

1. Selectivity: only aware of a subset of stimuli-- selective attention. 2. Capacity Limitations: limited ability to handle different tasks or stimuli at once--divided attention. 3. Sustained mental effort: limited ability to engage in protracted thought, especially on the same subject--vigilance. 3 meanings of the word ‘Attention’

PSBONKG###### Attentional Blink You will see a stream of letters rapidly presented in the center Group 1: memorize any vowels Group 2: memorize any vowels and red letters

Target 2 S N O B Target 1 Encoding into Working Memory

Attentional Blink: Early or Late Selection? Instead of letters, use words. An initial word establishes context (e.g., milk) Target 2 is a word that is semantically related to the context word or not (e.g., sugar, shoes) When subjects fail to report T2, look at their brain waves (ERPs) to assess whether the meaning of that target has been processed or not N 400 (ERP marker of semantic processing)

Spotlight metaphor - metaphors are not right or wrong, they are useful or not…