attention to visual search (week 4)

Question 1

what is inattentional blindness?

Answer 1

we overestimate how much of the world we are aware of, even very salient (e.g., attention-grabbing) things can be missed

Question 2

what was concluded about inattentional blindness from the original gorilla study (Simons & Chabris, 1990)?

Answer 2

Inattentional blindness:
1. can be induced easily in healthy participants
2. occurs more frequently if the display is transparent
3. depends on the difficulty of the task - the more primary tasks occupy attention, the less likely they are to see the gorilla

Question 3

what is the central capacity theory (Kahneman, 1973)?

Answer 3

a single central capacity that can be used flexibly - participants talked on a hands-free mobile from whilst driving in a simulator - ERPs elicited by the onset of a pace car’s brake light when talking on a mobile phone and when not talking on a cell phone

Question 4

what is change blindness?

Question 5

what is the attentional blink?

Answer 5

we can make something invisible by showing it too people very quickly after we’ve shown something else that is important to them (Raymond & Shapiro)

Question 6

what are the key ingredients to investigate the attentional blink?

Answer 6

1. rapid visual stimuli (at ~10Hz)
2. participants asked to look out for two targets and report if they saw them at the end of each trial
3. the first target is referred to as T1, the second as T2

Question 7

what happens to T2? (Luck et al., 1996)

Answer 7

T2 is processed by our brains, even if we have no conscious experience of seeing it - in the study from luck et al, (1986) the N400 is the same size regardless of the time passed since T1, demonstrating our brain did some processing of what it means

Question 8

what is the N400?

Answer 8

the N400 is a negative event-related potential (ERP) that can be seen when our brains access the meaning of almost any stimulus - the N400 reflects cognitive processes related to accessing the meaning of a stimulus

Question 9

theories of the AB: what is the interference theory (Shapiro et al., 1994)?

Answer 9

T1, T2 and their masks (distractors) are all encoded into a temporal buffer e.g., visual short-term memory - the AB is competition for retrieval amoun all items in short-term memory?

Question 10

what is the evidence for interference theory?

Answer 10

Isaak et al. (1999) reported that the AB increases with increasing numbers of distractors - a unified model: due to the distractor following T1, increased attention is required to process T1 which leaves less attention for processing T2, therefore leaving T2 vulnerable to decay or interference from distractors

Question 11

what is the cocktail party problem?

Answer 11

Unattended auditory information is processed to a lower level of complexity than attended information - we are better at paying attention to something, if the thing you have to ignore is something you have experience in

Question 12

attention as early selections: broadbent’s (1958) theory - (theories of selective attention)

Answer 12

1. parallel input into sensory register
2. inputs are then filtered on the basis of physical characteristics - this prevents overloading of limited capacity, and the remaining inputs are available for later semantic processing
3. but… some parts of the unattended stream are processed semantically (e.g., hearing your name in a conversation you aren’t paying attention to)

Question 13

attention as late selection: deutsch and deutsch’s (1967) theory - (theories of selective attention)

Answer 13

1. all stimuli are fully analysided - the bottleneck occurs late, and the most relevant stimulus determines what response is made
2. but… early sensory ERPs are smaller if unattended, which places the bottleneck much earlier during processing

Question 14

attention as flexible selection: Treisman’s (1960) leaky filter - (theories of selective attention)

Answer 14

1. unattended information is filtered after the sensory register
2. stimulus analysis proceeds through a hierarchy from physical characteristics of the stimulus up to its meaning and beyond
3. when capacity is reached, tests at the top of the hierarchy are precluded for all but the ‘attended’ stimulus
4. precise location of the bottleneck is more flexible than broadbent’s model

Question 15

when is attention selection happening?

Answer 15

1. initially the field considered a distinction between early and late selection
2. in reality it is probably flexible and influenced by many top-down and bottom-up processes

Question 16

what is the posner cueing paradigm (covert attention)?

Answer 16

sighted people can pay attention to a part of space that they aren’t directly looking at - called “covert attention” - posner (1980) designed a paradigm to measure how that works

Question 17

what were the results of the posner cueing paradigm?

Answer 17

endogenous attention - choosing to pay attention to a particular part of space makes you react faster to things that happen in that part of space
exogenous attention - the same is true if your attention is draw to that part of the space without you intending to, but only if the something happens in that part of space very quickly after you shift attention to it

Question 18

what are Posner’s attentional systems?

Answer 18

the endogenous system - comes from within us and is controlled by an individual’s intentions and expectations, involved when central cues are presented (top-down)
the exogenous system - automatically shifts attention to things that are important, involved when uninformative peripheral cues are presented, stimuli that are salient or that differ from other stimuli are most likely to be attended (bottom-up)

Question 19

what are the visual search paradigms?

Answer 19

feature search - target has a unique feature that is not shared by other items and therefore “pops out”
conjunction search - target has no unique feature that is not shared by other items

Question 20

what is feature integration theory (FIT)? (Anne Treisman.,1988:1992)

Answer 20

1. perceptual features are encoding in parallel and prior to attention - if an object has a unique feature, it may be detected without the need for attention.
2. if an object shares features with another object, then it cannot be detected from a single perceptual feature, and spatial attention is needed to search all candidates serially.
3. in other words, an object is only an object if you pay attention to it

Question 21

what are the stages of visual search?

Answer 21

1. rapid initial parallel process to identify features
2. next a slow serial process to form objects by combining features

Question 22

what is the evidence for feature integration theory?

Answer 22

1. illusory conjunctions (or features) can occur when focussed attention is absent, relevant stored knowledge is absent, when spatial attention is diverted, and when display is presented in peripheral vision
2. illusory conjunctions are not just guessing - they can occur with high confidence and they do not occur under all circumstances that decrease performance

Question 23

what is the evidence against feature integration theory?

Answer 23

1. FIT argues that an object is only an object if attended to, however, negative priming tasks show semantic processing of unattended stimuli
2. FIT argues you have to pay attention to the features in order to bind them to an object - but here we have evidence that even if you aren’t paying attention to it, an object can change the way you respond to a subsequent object

Question 24

what is priming?

Answer 24

when you present someone with some sort of stimulus (a prime), and then you present them with another stimulus (a target/probe) - the prime can then be manipulated in terms of its relation to the probe, in order to change the speed of which people can make decisions about it

Question 25

what are the strengths and weaknesses of feature integration theory?

Answer 25

strengths: important contribution to the explanation of what happens within the attentional spotlight
weaknesses: doesn’t explain why the similarity of distractors is influential, and neglect/extinction patients have problems with both conjunctive and single-figure targets

Question 26

what is the guided search theory/dual path model (Wolfe, 1998)?

Answer 26

1. in real life, people have expectations of where to find certain things - prior knowledge makes search more efficient
2. unlike FIT, where processing moves from parallel (pre-attentive) to serial (attentive), Wolfe assumes a simultaneous mix of serial and parallel strategies for visual search