Selective attention II

What do we use to direct our attention

• Locations, where is the object we want?

• Features, colours/contrasts/orientation

• Objects, single and groups

What do we consider in object based attention

• Features

• Objects

What are the models of attention

• Spotlight

• Feature integration theory (FIT)

• Integrated competition hypothesis

What is object based attention

The visual processes that select a segregated shape from amongst several segregated shapes

What is feature based attention

Enhances the representation of image characteristics throughout the visual field, useful when searching for a specific stimulus feature

Feature integration theory, Treisman 1980,1998)

• Attention was conceptualised as the glue that binds visual features encoded by separate anatomical modules

• Based on behavioural evidence of a qualitative distinction in performance in visual search tasks

• Accounts for the difference between features and conjunction searches

• Not all conjunction searches are slower than feature searches

What are biased competition models

• Selection is the result of competitive interactions between objects

• Stimuli presented within a receptive field generates strongest competition

• Competition can be biased by bottom up and top down processes

• Competition co-ordinates activity in distributed cortical regions

Feature based attention study (Martinez-Trujillo et al 2004)

• Trying to figure out how attention might operate across objects that are distributed across the visual scene

• Eg with a flock of birds very hard to pick out a single bird from an entire flock, you see a pattern

• They used random dots, a drifting field of dots

• They want to present these stimuli and use the dual task paradigm

• Manipulated attention but not the stimulus

• When we select the periphery we enhance our neural response

• Tried to see if we continue that periphery across our neural field and results showed that we do

• No change in stimulus but a change in the response of neurones

What is the emotional superiority effect (Maratos et al, 2008)

• Important in social interactions to have a sense of how people feel and looks at selection over time

• This experiment presents lots of different faces in a sequence very close together in time with no expression (jumbled up faces)

• We are evaluating what features are important when competing for attention

• Found that when two faces are presented close together it is harder to identify the second one

• The second face would be competing for selection

• There is a constraint of your ability to report the faces when they are close together #

• If the second face has a particular emotion expression, you are much more likely to report it however if it is neutral it is much less likely to be seen

What does feature and object based attention focus on

• Selective attention enhances perceptual processing at locations

• Enhancement is constrained by perceptual information that governs object recognition

• Attention can be directed towards non spatial features eg colour

• Feature and object based attention focus perceptual resources upon relevant items across the visual field