Kap. 4 - External attention

What is the distinction between internal and external attention?

• Are they completely unrelated to each other?

Attention

• Family of cognitive mechanisms that combine to help us select, modulate, and sustain focus (vigilance) on information that relevant for behaviour

• Helps us select and prioritize information because of our capacity-limited ability to process information

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External attention

• How we attend outwardly/select and modulate sensory information

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Internal attention

• How we select, modulate, and maintain internally generated information

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Relation to each other

• Useful to talk about them separately, but they are closely related

• Can influence each other!:

  • E.g.

    • Attention on daydreaming (internal) interferes with ability to attend to lecture (external)

Can you always tell where people are paying attention? Why/why not?

Overt attention

• “Outwardly observable sign of where people are paying attention”

• Measuring overt attention:

  • Eye tracking

    • Cameras recording saccades (eye movements)

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Covert attention

• Attention directed in a way that can’t be discerned by observable signs

  • “Processing an object or location in visual scene without shifting gaze“

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Does overt attention always correlate with covert attention?

• Attention is a function of the mind, not just the eyes

• Overt attention often match with covert, but not always!

  • E.g.

    • Experiment: Inattentional blindness with radiologists not covertly attending to the monkey, even though overtly seeing it

Describe different ways that attention can select information from the world

Selection

• “Singling out certain pieces of information among many

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Spatial attention

• “The ability to attend to regions in space“

  • Like a spotlight - illuminating and raising the profile of whatever falls within its focus

    • Enhances information in specific location and suppress information outside that location

  • Like a zoom lens - attentional resolution decreases as attentional breadth increases

    • Consistent with fMRI:

      • Attention to larger area visually —> spread of corresponding neural activation (in visual system) increased, but neural activity level within spread decreased

• E.g.

  • Posner cueing task

    • Faster and more accurate at responding to a target (in space) when a cue (in this case and arrow) predicts the target’s location

      • Slower if cue is invalid and doesn’t predict target

      • The difference of speed in reaction to valid vs invalid cues is used as index of movement spatial attention

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Feature-based attention

• “The ability to attend to or filter out information based on features like color, shape or motion“

• Neuroimaging:

  • Neural distinction between feature-based attention and spatial attention

  • Feature-based turning of attention often occur when preparing to search for a target that hasn’t appeared yet

  • Feature-based attention increase activity in neural regions that are sensitive to the target feature across the visual field

    • - even in absence of sensory stimulation

    • Neurons that are not responsive to the feature tuned to be prioritized exhibit suppressed sensitivity

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Temporal attention

• “The ability to pay attention to points in time”

• E.g.

  • Attentional blink

    • The second of two targets shown in rapid succession of items → more difficult to detect than the first

      • (within ca ½ a second)

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Object based attention

• “Selective attention to an object rather than to a point in space“

  • Objects as units of attention - i.e. attention to a part of the object entails attention to the whole object

  • Evidence

    • E.g. - reaction to cue and target within the same object vs in different objects (s. 88)

      

      • Result: The invalid cues slowed response time more when they appeared on the opposite rectangle than on the same rectangle as the target

      • Meaning of result: Visual attention is influenced by how we parse the world - (with objects as a unit of attention)

    • Spatial neglect by lesion in right hemisphere

      • Fail to process stimuli within left visual field - some fail to process left side of objects!

        • - even situated in their right visual field

How have researchers distinguished between voluntary and reflexive attention?

Voluntary attention

• The effort to select goal-relevant information

• Endogenous (central) cues in Posner cueing task

  • Engages voluntary attention and can appear between the potential target locations and can indicate symbolically where the target is likely to appear

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Reflexive attention

• Attending to a particular stimulus because it has seized your attention

  • Instead of you actively choosing to attend to it

• Exogenous (peripheral) cues in Posner cueing task

  • Engages reflexive attention and can appear at one of the target locations instead of between them

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Evidence to distinguish the two attentional mechanisms:

• Neural regions involved

  • Voluntary:

    • Certain areas along the dorsal portion of brain

  • Reflexive:

    • A network alongside the ventral side of brain

• Time course

  • Reflexive attentional shifts:

    • Transient:

      • Benefits of reflexively processing stimuli at specific location peak after ca 150 ms

      • After 150 ms —> inhibition of return

        • Short period when processing at the location is suppressed

        • Aiding ability to find things!

What is the biased competition model of attention?

One of the most influential and empirically supported models of attention!

Claims:

• “Stimuli in a cluttered visual environment compete with each other to drive the responses of neurons in the visual system”

  • i.e.

    • (A given neuron’s preferred region of the visual field is known as that neuron’s receptive field)

    • The competition among stimuli is particularly fierce when they fall within the same perceptive field

      • The smaller the distance among the stimuli - the greater overlap in the neuron populations that are activated —> increased competition among neural representations

• “Selective attention biases the competition in favor of one stimulus over the others“

  • Selective attention is biases by:

    • Bottom-up selection

      • Salience of the physical features

    • Top-down selection

      • Goal-relevance

  • Bias may be amplified by emotional arousal

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The model is supported by evidence of neural activity

• When competing stimuli simultaneously occupy a neuron’s receptive field, the visual cortical neuron highly sensitive to another stimulus - become less responsive

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Ambiguity resolution theory (of visual selective attention)

• Any one cluster of neurons can actively support several representations

  • So, presence of multiple stimuli —> ambiguity about which mental representation accurately reflect the external world

• Resolution: Attention

How do early selection and late selection accounts of attention differ?

• How do load theory and Treisman’s attenuator model fit in with/modify this distinction?

• What evidence supports these different accounts?

The relevant question: “at what point in the flow of information processing does attention do its selecting?“

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Early selection of attention

• The attention theory that we attentionally select stimuli on the basis of physical features - such as color, pitch, or location - and that we register their meaning only after we have selected them

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Late selection of attention

• The attention theory that we process the meaning of everything around us before we select what will gain entry to heightened awareness

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Treisman’s attentuator model

• Claims: “Meaningful information needs to meet a lower threshold of processing in order to reach awareness“

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Load theory of attention: - flexible locus of attention

• Availability of mental resources to process information depends partly on the demands of an attended task

  • If attended task has high load (demanding):

    • Few spare attentional resources for unattended information - filtering it out at early processing stage

      • Unattended information will not reach awareness nor interfere with attended task

  • If attended task has low load:

    • More spare attentional resources for unattended information - may let attention “spill over” to this

      • Unattended message more likely to reach awareness + interfere with task

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  • Perceptual load

    • Load is high because of difficult perceptual demands

    • Processing of non-targets is diminished

  
  

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  • Working memory load

    • Load is high because of taxing working memory

    • Processing of non-target information increase

      • Since working memory plays role in inhibition - inhibiting distractors is harder if higher load

What is preattentive processing, and what might our experience of the world be like during this stage of processing?

Reality: - a combination of early and late selection!

• Attention actually operate at many points in the information processing

  • Preattentive processing

    • The extent we process information before attentionally selecting it

  • Parallell processing

    • Analyzing of stimuli during preattentive processing - taking in stimuli quickly all at once

  • Serial processing

    • Further analyzing of stimuli as they get attentionally selected - more slowly and one bit at a time

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Evidence for different types/stages of selection

• Visual search task - parallel processing

  • Look for a target embedded in non-targets

  • Results:

    • When target is characterized by a distinctive feature (“popping out”): detection is quick — parallell processing

    • When target is charactarized by a conjuction of features: detection is slower

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• Feature Integration Theory - preattentive processing

  • Suggests:

    • During preattentive processing, we experience the world as a jumble of simple features that are not bound together into cohesive objects

    • Focusing on an object binds the features together - perceiving meaningful object

  • Evidence/support:

    • Illusory conjunctions

      • Incorrect binding of features in front of us

      • E.g.

        • Task:

          • When flashed arrays of four letters - asked to report identities of two digits + the colors and positions of the letters

        • Result:

          • Errors tended to reflect the incorrect combining of features presented

        • Ergo:

          • We process features prior to selection, but need attention to combine them accurately

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• Dichotic listening - preattentive processing / early selection

  • Task:

    • Listening to two different messages played simultaneously - actively only paying one of them attention (repeating this message out loud)

  • Result:

    • Barely able to report anything about the unattended message:

      • Only the physical properties of the stimuli

        • Like: gender switch / pitch, and replaced voice by a 400Hz tone

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  • Broadbent’s filter model of attention

    • Describe: “the flow of information processing pre- and post-attention“

      • Suggests: “information is attended / ignored based on early stimulus characteristics“

        • i.e. - based on physical properties before prior to semantic processing of meaning

      • Evidence against this model:

        • Words with relevant meaning: People noticing their own name when presented to the unattended ear

          • (Treismann’s attenuator model as resolution to this problem)

How are modulation and vigilance functions of attention different from the selection function of attention?

Selection of attention

• Acts like spotlight and filter out information - focusing on specific information

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Modulation of attention

• Attention’s ability to change the way we perceive a stimulus

  • i.e. Changes strength of neural processing for the selected stimuli

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Vigilance of attention

• Attention’s ability to highten attentional anticitpation, enabling us to better respond to stimuli before they appear

  • i.e. Maintains readiness over time

What evidence suggests that attention modulates our perceptions?

Study with Gabor patches

• Test:

  • Presented with two Gabor patches, asket to determine which of them had the highest dark/light contrast + the tilt

  • Patches were preceded by attention-grabbing cue in between flashes or at one of the patch locations

    • Goal: manipulating where allocating attention

• Result:

  • When cue flashed in between:

    • bias in reporting the tilt of one over the other

  • When cue flashed at one of the locations:

    • Perceive that patch as having higher contrast

• So,:

  • Spatial attention modulates how people perceive the visual qualities (i.e. contrast) of a stimulus

How are measures of attentional vigilance relevant to the real world?

When given information about when a stimulus will appear, people are faster to respond to the target than when they are given no warning

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E.g.

• Continous performance task

  • Stay “on task” for a prolonged time period

  • Understanding factors that enable people to stay vigilant during such tasks has real-world importance

    • Factors e.g.: brain damage or little sleep

    • E.g. Baggage screeners at airports - looking for specific objects

      • Bad at detecting targets that appear rarely

Describe at least one way that inattentional blindness and change blindness differ from each other?

Inattentional blindness

• When people fail to notice an unexpected item right in front of their eyes when their attention is preoccupied

• Influenced by expectations

  • (i.e. expecting to see the gorilla, but not the color change of the curtains)

  • i.e. radiologists looking for nodules in lungs, but not covertly seeing the gorilla

• Influenced by feature-based attention

  • i.e. “driving through” imaginary world on video, looking for a road sign with specific color - less likely to collide with motorcycle if it had the same color as the road sign

• Difference in overt and covert attention!

  • What is in covert attention depend on which aspect of visual information we select for further processing

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Change blindness

• Failure to notice large changes from one view to the next, and it reflects another, related failure of awareness in the absence of attention

• Difference from inattentional blindness:

  • Change blindness:

    • Can occur because people fail to compare two views of a stimulus in memory

  • Inattentional blindness

    • Occur because people fail to notice a stimulus at all

• E.g. - door experiment: asking for directions and changing the person

  • Result:

    • Many didn’t notice

  • Other suggestions based on results:

    • Likelihood of noticing the change depends on what aspect of the person’s appearance attended to:

      • If out-group member —> only encoding features enough to classify as out-group

      • In-group —> encoded more individuating features

What is one piece of evidence suggesting that attention and awareness may not be the same thing?

Attentional blink

• Test - finding two targets in a rapid serial visual presentation task

  • Pushes attention to its temporal limits

    • Increasing difficulty of attending to some stimuli because they appear too soon after another

  • Result:

    • Typically difficulty reporting the second target, it appearing too soon after the first target

  • So,

    • If attention is fully occupied, you can look directly at a stimulus without being consciously aware of it

      • i.e. focused attention is a required gateway for a stimulus to cross the threshold into conscious perception - without attention, no conscious perception

If we can be aware of only a few things at a time, why do we often feel like we experience a richly detailed world in any given moment?

• We can rapidly process the “gist” - the overall idea - of a scene more quickly than we can process a scene’s details

  • The gist information helps give a sense of a richly perceived world

  • Perception of the world is a construction of the mind:

    • Stitches together immediate sensory information with information from immediately preceding views

What are some factors that can guide our attention without our control or intention?

Attentional capture

• Stimuli that can draw our attention reflexively

• E.g.

  • Arrows - pointing in a direction

  • Eyes - looking in a direction

  • Exogenous cue flashing at location of upcoming target

  • High salience aspects (very different from surroundings)

• Saliency map - some cues have more power than others

  • In early processing, visual system computes the relative differences between visual signals across the visual field - forming topographical representation

  • E.g.

    • Response time slows if high salient distractor is shown (e.g. an irrelevant different color)

  • Overriding attentional capture by irrelevant information

    • If tuned attention for a particular feature

      • (i.e. if they know that a specific type of salient (e.g. sudden onset or different color) distractor will appear )

Describe different ways that emotion and learning appear to influence attention

Experience and learning directs attention

• Contextual cueing

  • Learning where to attend and what to expect based on statistical regularities in past experience

    • An effect that is observed when people search for a target in an array of non-targets over and over again, across many trials - faster at finding a target in repeated configurations

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Emotion-driven guidance of attention

• Emotion-driven attentional bias

  • When we show a preference to attend to emotional stimuli

  
  

• E.g. emotional influence on selection

  • Emotional disorders:

    • Heightened tendencies to attend to emotionally negative information

    • E.g.

      • Dot probe task

        • Test:

          • Try to respond quickly to a target that can appear in one of two locations

          • Prior to target, locations are occupied - one with threatening stimulus, the other neutral

        • Result:

          • Anxious: Respond more quickly if target appears where the threat was

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  • Emotion and temporal attention

    • Attentional blink

      • If first target is emotional, it causes more impairments for detection of the other stimuli

      • Connected to amygdala - if lesion, then this effect doesn’t occur

    • Emotion-induced blindness

      • The failure to see rapidly presented targets that appear right after a rapidly presented emotional non-target

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  • Value-modulated attentional capture

    • The reflexive allocation of attention based on learned value

    • E.g.

      • Doing a task where you know you’ll gain money - higher stakes —> worse performance

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• E.g. - emotional influence on modulation

  • Emotional face shown before Gabor patch —> contrast sensitivity increased for the task

    • Effect was independent of spatial location - when faces appeared in different location as Gabor patch

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• E.g. - Broaden-and-build theory on emotional states affecting attention

  • Positive emotions —> widen range of information people readily consider and attend to (global bias)

    • But if positive emotion is an “approach motivation” —> less likely to have global bias

  • Negative emotions —> narrow range of information people consider