attention Flashcards
what are unattended stimuli?
pieces of sensory information that are present in the environment but do not receive conscious attention and full processing in the brain
what is the early selection theory of attention?
unattended information stops being processed at the perceptual stage and thus we shouldn’t know the meaning of unattended information
what is the late selection theory of attention?
that unattended information, even if selected against, will be processed at quite a high level, and the limitation lies at the capacity for action but allows for the selection of meaningful objects
what does the existence of attention imply?
that we must select and withdraw from some things in order to effectively process others
we have a limitation to how much we can process, but where is it?
what are the experiments that support early selection?
auditory: Cherry 1953, cocktail party problem
visual: Rock and Gutman 1981, red/green memory test
neglect: patients copy just RHS of image and don’t know left side is there
what are the experiments that support late selection?
auditory: Moray 1959, cocktail party but w electric shocks for cities
visual: Rock and Gutman 1981, red/green negative priming
neglect: Marshall and Halligan, 2 houses, one burning, choose non-burning
Describe Cherry’s 1953 exp. about auditory selection
subjects listened to 2 different messages, 1 in each ear, and were asked to repeat back one of the messages
subjects were later asked about things said in the unattended message, they were unable to recall very much
if the unattended message was changed to a different language or even just a repetition of the same word subjects often didn’t notice
notice if the second conversation was replaced with a beep, or if the speaker’s gender changed due to the pitch shift in their voice
implies that only surface level perceptual processing is occurring to the unattended information.
describe the modified auditory selection experiment by Moray, 1959
subjects conditioned to expect electrical shock when they hear the name of a city
in the second, unattended message, random words are said interspersed with city names and participants are asked to press a button when they hear cities in the unattended message
due to previous conditioning, they become nervous and sweat on hearing city names, even though no shock is given. Significant galvanic skin response can be seen to occur when city names appear in the unattended message, even when subjects cannot remember hearing them, and when the city names are not ones to which they have been conditioned
the subject must be extracting semantic meaning from the unattended information, identifying it as a city and then associating it with the electric shock, supporting the late selection theory.
describe the Rock and Gutman visual selection task (1981)
2 objects are shown overlapping on a screen, 1 in red, 1 in green
asked to judge pleasantness of red object
later on given test about objects: remember most of red but rarely remember unattended green objects
implies little processing of the objects has occurred outside the subjects of attention
describe the modified Rock and Gutman 1981 experiment that supports late selection
subjects are asked to make a speeded judgement about the red object as quickly as possible by pressing a button
key manipulation = stimuli appearing in successive trials, with 1 that appeared in green before appears in red in 2nd trial (thus requires response)
‘negative priming’, subjects are about 20ms slower to respond in the current trial if the object was unattended on the previous trial
suggests higher level of processing has occurred for that object when it was unattended the first time, because something is interfering with the current processing of it
Additionally, if a green cat is seen in trial 1 followed by a red dog in trial 2, it will still take longer for the participant to respond, even though the objects are only semantically related
describe the unilateral neglect experiment supporting early selection
lesion in right hemisphere
patients unresponsive to stimuli in contralateral hemifield
If asked to copy the whole image, affected patients will just copy the RHS, without even being aware that the left hand side is missing
suggests pathological bias towards processing on the right rather than the left, and the occurrence of little processing outside attention
[Marshall and Halligan]
describe the unilateral neglect experiment supporting late selection
if patients presented with 2 images of houses, in which 1 was on fire on the LHS and asked them to choose which house is more appealing, initially say they are the same
if pressed while choose the house not on fire 9/11 times
some degree of high level processing of meaning of unattended information, of which the patients are completely unaware
and so why can we not prove either the late or early selection theory?
not early: high level processing happening in neglect
not late: evidently not all info is processed up to the high levels, seen in fMRIs of lateral geniculate nucleus + V1 (clear advantage for attended over unattended)
what is difficulty better described as in the case of attention
high perceptual load i.e. a lot of sensory-perceptual info coming at you
(also high cognitive load)
therefore how can we reconcile the evidence for early and late selection?
flexible selection: we have fixed capacity for processing information but the point at which we select for attended info depends on the perceptual load of the task
how does the amount of unattended info we process relate to the perceptual load of the task?
inversely proportional
