Selective attention I

What is selective attention

• Prioritisation of a subset of information and where we direct our attention

• Our brain receives information from multiple sensory systems and not all of it is relevant so it is important to select out only the crucial information

What determines spatial resolution

The gradient of visual acuity sampled in a single fixation

What is covert attention

• Ability to select locations or objects that are most likely to be relevant when making eye movements

• Prioritises areas (objects) for action (eye movements)

• Also prioritises information for analyses and retention

Post perceptual processes in selective attention

• Working memory, has about 4 objects and 4 locations

• Capacity limited temporal store,

• Verbal STM ( 7+2)

• Verbal VM ( <=4)

What is accuracy of recall determined by

• Capacity/ load * decay

• When we select we are accessing a small amount of information for our capacity limited temporal store

• Attention enhances accuracy of recall

• Decay function (exponential)

• Selective attention gates access to verbal working memory (reduces load)

• We perceive something, bring our attention to it then it gets stored in our short term memory

How does selective attention protect capacity limit

• Effector systems (eg our eyes and hands)

• Cognitive systems (VWM) and cortical computation

• Selection biases perceptual sampling and post perceptual processes eg what we encode and the capacity of it

What is orientating attention (Muller and Rabbitt, 1989)

• Attentional guidance can be:

• Exogenous (bottom up), stimulus driven

• Endogenous (top down)

What is exogenous attention

• Stimulus driven (bottom up) capture of attention by salient signal eg bright flash

• It is usually involuntary because the attention is captured by non predictive cues

• Has a fast time rise

• Inhibition of return (IOR)

What is endogenous attention

• Goal driven (top down) selection

• Slow rise time

• Long lasting bias therefore no evidence of inhibition of return

How can we measure attention

• Selective attention is a cognitive construct used to explain behaviour

• It isn’t directly measurable

• We can’t process everything however we can orient attention around the world and select particular objects

• We manipulate stimuli and measure changes in behavioural and physiological responses to make inferences about selective attention

Attention and spatial acuity (Montana et al 2009)

• Investigated the effects of exogenous and endogenous cues on spatial acuity

• (The ability to discriminate between smaller features)

• Argued if shifts of attention are used to allocate limited capacity perceptual resources:

• Spatial acuity at cued locations should be > uncued baseline

• Spatial acuity at uncued locations should be < uncued baseline

Attention and signal to noise

• Previous studies present stimuli very fast to make discrimination difficult

• Objects outside the lab are often accompanied by noise eg:

• Occluding objects in visual scenes

• Competing voices in auditory scenes

Dosher and Lu noise exclusion mechanism

• Investigated whether attention includes a noise exclusion mechanism

• Looked at the target contrast first but then evaluated how external noise affected the process

• Need to inhibit the irrelevant contrast

• Target contrast was that observers were required to obtain 62.5% accuracy

Attention and signal to noise results

• Discriminability of the target at cued locations was higher than uncued locations

• The affect of cueing was more pronounced in displays containing high levels of external noise

• Selective attention increases detection at cued location by increasing signal to noise ratio

Auditory selective attention (Spence and Driver, 1997,1994)

• Investigated benefits of auditory spatial attention using an “orthogonal” cueing paradigm

• They manipulated the top down knowledge

What is selective auditory attention

• Increases spatial acuity of auditory localisation

• Increases acuity of non spatial judgements

• Protects selected items from degradation in auditory working memory

• Exogenous and endogenous cues produce similiar benefits but have different time courses

Results of Montana’s study

• Spatial acuity at cued location was significantly higher than uncued baseline

• Concomitant decrease in acuity at uncued locations

• Based on the data, covert attention mediates changes in observers spatial acuity in the absence of eye movement

• Using prior knowledge to make eye movements