Chapter 3. Attention

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Chapter 3. Attention

• OVERVIEW
• Selective attention (cognitive tunneling)
• Pay attention to multiple things in sequence
  intentional but unwise choice
• Focused attention
• Pay attention to 1 thing tendency to be
  distracted by external environmental info.
• Divided attention
• Pay attention to multiple things at the same time
  simultaneously- limited ability to time sharing
  performance
• SELECTIVE ATTENTION
• Visual Sampling
• eye and visual sampling ? seek information and
  searches for targets
• Visual scanning behavior (attentional
  searchlight)
• Eye fixation system
• Fovea area perceives detail about 2of visual
  angle

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• Pursuit movement the eye follows the target
• Saccadic movement
• discrete, jerky from one stationary in the visual
  field to next
• Sometimes superimposed on pursuit movement
• Saccade suppresses visual input
• Fixation display info. processed during
  fixation
• Location center of the fixation
• Useful field of view diameter around the
  central location which info. is extracted
• Dwell time how long the eye remains at that
  location
• Supervisory control context
• scans the display of a complex system under
  supervision
• allocates attention through visual fixations to
  various instruments
• the target is known
• Target search context
• scans a region of the visual world
• a targets location and existence is unknown

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• Supervisory Control Sampling
• Optimality of Selective Attention
• stimulus environment -- channels and critical
  events
• Mental model guides sampling
• form a mental model of the statistical properties
  of events frequency and correlations
• Adjustment to event rate sluggish beta
• the sampling rate is not adjusted with event
  frequency
• Sampling affected by arrangement more likely to
  make horizontal scans than diagonal scans
  simplifying rules and heuristics
• Memory imperfect sampling imperfect sampling
  remainder
• Preview helps as the number of channels
  increases, fail to take advantage of preview
• Processing strategies cognitive tunneling
• failed system, delayed feedback
• Eye Movement in Target Search
• Environmental Expectancies
• fixate most on areas of containing the most
  information (Yarbus, 1967)
• a scan path over same picture dependent upon
  seeking info. (Yarbus, 1967)
• Display Factors and Salience
• neither consistent pattern of display scanning
  nor optimal scan pattern in search

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• certain display factors to the allocation of
  visual attention
• salience and abrupt stimulus onset in the visual
  periphery may bias decision making
• presence of unique stimuli (singletons) slowed
  the detection of other targets
• physical location in the display the upper
  left, concentrated on the center (edge effect)
• dominated by conceptually or knowledge-driven
  scan strategies
• Display-Driven and Conceptually driven processing
• they commonly interact standardization of
  roadway and sign design
• positive guidance forecast the unexpected event
• Search Coverage and the Useful Field of View
• the highest acuity region of fovea an angel of
  no more than 2 degrees
• UFOV a circular area around the fixation point
  -- 1 to 4 degrees of visual angle
• size determined by the density of information
  the discriminability of the target
• aging restricted UFOV
• training enlarge UFOV, benefits are equal across
  age groups
• reduction in UFOV has serious implication such as
  driving
• UFOV is sensitive to task demand in the foveal
  region
• Fixation Dwells
• survey dwells short, used to establish the
  regions more likely to contain a target
• examination dwells used to provide a detailed
  examination of the region for an embedded target

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• difficulty of information extraction
• low familiarity, low frequency, and out of
  context higher information content (longer
  dwells)
• expertise
• Visual Search Models
• How long to find a target? What is the
  probability in a given period of time?
• Drurys Model (1975, 1982)
• 1st stage target search stage
• the probability of locating a target increases
  with more search time (fig. 3.2) diminishing
  rate
• 2nd Stage decision stage
• uses the expectancy of flaws to set a decision
  criterion
• Variables affecting search speed (fig 3.3)
• the number of elements to be searched serial
  search (50 msec/item)
• exceptions to serial search one level along one
  salient dimension
• greater search efficiency for parallel than
  serial
• preattentive (requiring few attentional
  resources) for parallel and attentive for serial
• serial search the target is difficult to
  discriminate from distractors
• exceptions to serial search the presence of
  features rather than absent
• different discriminabilities of targets in the
  two situations

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• dispersion of targets -- scanning distance and
  visual clutter trade off
• any of several different target types slower than
  only one
• exception a single common feature
• extensive training automaticity ? parallel
  search (consistent mapping not varied mapping)
• Structured Search
• Basics
• information that may help guide the search is
  available
• Application Menus
• target items are reached in the minimum average
  time (fig 3.4)
• linear visual search model frequently searched
  items positioned toward the top of the menu
• optimal number of items per menu is between three
  and ten (Lee and MacGregor, 1985)
• criterion-based model (Pierce, Sisson, and
  Parkinson, 1992)
• the effect of similarity in menu search
• Directing Attention
• advise an operator in advance where attention
  should be directed
• more accurate as the stimulus-onset asynchrony
  between the warning (cue) and the target
  increases SOA200ms more effective than
  SOA50ms
• peripheral cues (out of foveal area) more
  effective with short SOAs, a transient effect,
  stimulus-driven, automatic process
• central cues more effective with longer SOAs,
  long lasting, goal-directed, controlled
  interpretation

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• PARALLEL PROCESSING AND DIVIDED ATTENTION
• Preattentive Processing and Perceptual
  Organization
• visual processing of a multiple-element world
  two main phases
• preattentive phase (STSS, automatic, grouping)
  and attentive phase (perception, selecting)
• Gestalt psychologists (fig 3.5) items to be
  preattentively grouped together on the display --
  proximity, similarity, common fate, good
  continuation, closure ? high redundancy
• all items of an organized display must be
  processed together to reveal the organization
  (parallel processing) -- global or holistic
  processing
• single object within the display -- local
  processing (fig 3.6) -- response conflict
  global precedence
• emergent features global property of a set of
  stimuli (displays) (fig 3.8)
• global processing tends to be preattentive and
  automatic -- reduce attentional demands
• Gestalt principles produce groupings or
  emergent features
• spatial proximity of different elements
  compatible with task demands
• Spatial Proximity
• Overlapping Views The Head-Up Display
• although spatial proximity will allow parallel
  processing, it certainly will not guarantee it
• Neisser and Becklin (1975) separation defined
  not only in terms of differences in visual or
  retinal location but also in terms of the nature
  of the perceived activity
• Wickens and Long (1995) an unexpected obstacle
  was detected more poorly with the HUD than with
  the head-down configuration -- HUD could improve
  control of position during landing, both in view
  and when the runway was obscured by clouds

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• the HUD appears to facilitate parallel processing
  of scene and symbology when the pilot expects the
  stimulus and interferes when the stimulus is
  quite unexpected
• conformal nature of the symbology
• Visual Confusion, Conflict, and Focused Attention
• spatial proximity confusion
• spatial density little effect on visual search
  time
• Wickens and Andre (1990) -- critical variable in
  predicting performance is the degree of spatial
  separation of relevant item from irrelevant, not
  the spatial separation between the relevant items
  themselves
• Holahan, Culler, and Wilcox (1978) to locate
  and respond to a stop sign in a cluttered display
  is directly inhibited by the proximity of other
  irrelevant signs in the UFOV
• Eriksen and Eriksen (1974) -- perceptual
  competition a failure of focused attention
  caused by the competition (ex. UHP)
• response conflict (ex. FHF), redundant gain (ex.
  HHH)
• Object-Based Proximity
• different attributes of a single stimulus object
  at one spatial location
• concurrent processing of elements lying close
  together in space (space-based model of
  attention)
• concurrent processing occurs when elements lie
  within a single object (object-based model)
• Stroop task subject is asked to report the
  color of a series of stimuli as rapidly as
  possible
• multiple dimensions belonging to s single object
  are likely to be processed in parallel
• integral dimensions produce a cost for a
  filtering task and a benefit with redundant
  dimensions

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• Applications of Object-Based Processing
• in cognitive psychology, an object has three
  features
• surrounding contours or connectedness between
  parts
• rigidity of motion of the part
• familiarity
• benefits of objects in two contexts
• conformal symbology mapping of display objects
  to real-world objects
• object displays multiple information sources
  are encoded as the stimulus dimensions of a
  single object
• Conformal Symbology and Augmented Reality
• conformal symbology helped the pilot divide
  attention between the display and the world
  beyond, align the display object to the real
  object, and reduce tracking error
• Object Displays
• parallel processing of object features to create
  multidimensional object displays (fig 3.10)
• The Proximity Compatibility Principle
• three ways in which multiple display channels can
  be integrated emergent features, spatial
  proximity, object integration
• proximity-compatibility principle whether
  different tasks are served differently by more or
  less integrated displays
• to the extent that information sources must be
  integrated, there will be a benefit to presenting
  those sources either close together, in an
  object-like format, or by configuring them to
  create emergent features

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• to the extent that information sources must be
  treated separately, the benefit of the
  high-proximity object display will be reduced, if
  not sometimes reversed
• close proximity increases the possibility of
  parallel processing
• close proximity and objectness can create useful
  emergent feature that help information
  integration if they correspond to the key
  variables of the task
• emergent features can hurt performance if they
  are not mapped into the task
• response conflict can result if proximity
  combines variables that require focused attention
  
• Color Coding
• benefits
• rapid localization
• capitalizes on population stereotypes
• tie together spatially separated display elements
• redundancy in combination with shape, size, or
  location
• limitations
• failure of absolute judgment five or six
  colors, glare or low illumination (affected by
  ambient light)
• no ordered continuum brightness (saturation)
  rather than hue
• population stereotype poor design with a
  conflict meaning
• irrelevant color coding can be distracting --
  display-cognitive compatibility

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• ATTENTION IN THE AUDITORY MODALITY
• omnidirectional no analog to visual scanning as
  an index of selective attention
• transient
• Auditory Divided Attention
• an unattended channel of auditory input remains
  in preattentive STAS (3 6 sec)
• attention switch
• on examined
• off LTM (preattentive) pertinent enough
  ?focused attention
• negative priming -- information presented in an
  unattended channel is temporarily inhibited for
  several seconds following presentation slower
• auditory object as a sound with several
  dimensions -- parallel processing
• Focusing Auditory Attention
• monaural and dichotic listening large benefits
  of dichotic over monaural listening in filtering
  out the unwanted channel
• cocktail party effect auditory selective
  attention (pitch, intensity, semantic properties)
• auditory attention can be directed by cueing
• Cross-Modality Attention
• parallel inputs across modalities
• redundancy gain -- speeds up processing
• dividing attention between modalities may be
  better than dividing attention within a modality
• visual dominance over auditory and proprioceptive

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