#14070 - Human Attention - Psychology

What is meant by the term ‘inattention’ and how does inattention affect information processing?

What is unilateral neglect? What studies of unilateral neglect told us about human attention?

What evidence suggests that we don’t process information about stimuli to which we are not currently attending? A) Studies of attention in healthy people b) neuropsychological studies of patients with visual neglect.

Definition of attention and inattention

Attention: Process by which certain information is selected, for further processing and other information is discarded. It is important to avoid sensory overload and attention is important in cognition.

-O’regan et al: Role of attention is shown by change blindness

• -When brief blank fields are placed between alternating displays of an original and a modified scene, identification of changes become extremely difficult even when changes are large and are made repeatedly.

• Identification is much faster when a verbal cue is provided showing that poor visibility is not the cause of this difficulty .

• Identification is also faster for objects considered to be important in the scene.

• These results support the idea that observers never form a complete detailed representation of their surroundings. In addition results show that attention is needed to perceive a change and attention is guided on the basis of high level interest

Evidence there is inattention

-Studies of attention in healthy people

Often studied in terms of visual attention- referred to as a spotlight- this highlights a particular location in space (e.g location contains a salient object) where there is a natural tendency for attention and eye fixation to go together because visual acuity- discriminating fine detail is greatest at point of fixation

Posner illustrated that attention operates on a spatial basis- participants were presented with three boxes on the screen in different positions; left, central, right- task of the participants was to press a button when they detected a target in one of the boxes

• At a brief interval before the onset of the target a cue would appear in one of the locations- the purpose of the cue was to summon attention to that location

• On some trials the cue would be in the same box as the target on others it would not-So cue is completely uninformative with regards to the later position of the target

• When the cue precedes the target by up to 150ms- participants are faster at detecting the target at that location- this is because the cue captured the attentional spotlight and this facilitated subsequent perceptual processing at that location

• At longer delays- above 300ms- the reverse pattern is found- participants are slower at detecting a target in the same location as cue- this can be explained by assuming that the spotlight initially shifts to the cued location but if the target doesn’t appear attention shits to another location- this is known as disengagement

• There is a processing cost in terms of reaction time associated with going back to previously attended location- this is known as inhibition of return

Cues for attention

In the Posner spatial cueing task- spotlight is attracted by sudden change in periphery

So attention is externally guided- this is known as exogenous orienting

Attention can also be guided by goals of perceiver- this is referred to as endogenous orienting

• -La Berge 1983: presented participants with words and varied instructions

  • -Participants were asked to attend to central letter and on another occasion they were asked to attend to whole word

  • -When attending to central letter, participants were faster at making judgements about the letter but not other letters in the word

  • -When asked to attend to the whole word they were faster at making judgments about all the letters.

  • -So attentional focus can be manipulated by the demands of the task

• -Another example of endogenous attention is called visual search- Spatial selective attention

  • -Participants are asked to detect the prescence or absence of specified target object- the letter F in an array of other distracing objects (E and T)- One theory of how we find targets in cluttered field is referred to as Feature Integration Theory/FIT- this theory is not only a theory of spatial/visual attention

    • -Theory explains that perceptual features such as colour and shape are coded in parallel and prior to attention

    • -If an object doesn’t share features with other objects in array it appears to pop out. However if distractors are made up of the same features that define the object- the object can’t be detected by inspecting th colour module alone or by inspecting shape alone- so to detect target one needs to bring together information about several features

    • -FIT assumes that this occurs by allocating the location of candidate objects- if the object turns out not to be the target then the spotlight inspects the next candidate and so on in a serial fashion

Space, attention, parietal lobes

• Parietal lobes- important role is spatial selective attention

• From the visual cortex the dorsal pathway is important for the where pathway- important in locating objects in space. Parietal neurons also respond according to behavioural saliency of a stimulus

• Patients with lesions to the posterior parietal lobe have a syndrome called hemi-spatial neglect- in which they fail to attend to stimuli on opposite side of space to the lesion- neglect is more severe following right hemisphere lesions resulting in failure to attend to the left- suggests there is hemispheric asymmetry suggesting that the right parietal lobe is more specialised for spatial representation than the left – this could be due to right hemisphere controlling attention across space

Importance of attention

-Sustained attention- the ability to direct and focus cognitive activity

-Important for attention, planning and intelligence

Neuropscyhological studies of patients with visual neglect

• -Patients with Blaint’s syndrome have damage to left and right parietal lobes- severe spatial disturbances- these patients only recognise objects one at a time, inability to reach in proper direction of an object under visual guidance, fixation of gaze without a primary deficit of eye movement

• Patients with visuospatial neglect fail to attend to stimuli on opposite side of space to their lesion- in more than 60% cases lesion is in the right hemisphere- neglect in the left space.

• This could be due to -Loss of neurons dedicated to representing parts of space, failure to shift attention to one side of space

• Testing for neglect:

  • patients omit features from left side when drawing or copying

  • In tests of line bisection patients misplace the centre of the line towards the right as they underestimate the extent of the left side

  • -Albert’s test of neglect: Cancellation tasks – where patients go through an array of objects and strike them through as they are found. They will typically not strike ones on the left. Increasing the...