Chapter 3. Attention

1. 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 2°of visual angle

2. 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 target’s location and existence is unknown

3. 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

4. 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

5. 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? • Drury’s 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

6. 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 – SOA=200ms more effective than SOA=50ms • 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

7. 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 oremergent 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

8. 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

9. 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

10. 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

11. 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