Subitizing And Counting: Preattentive And Attentive Processing In Visual Enumeration

Subitizing, the process of visual enumeration when there are fewer than four items, is rapid (40-100 msec/item), accurate and effortless. In contrast, counting, the process of enumerating more than four items is comparatively slow (250-350 msec/item), effortful and error prone. Why does this occur? In this paper an attempt is made to incorporate subitizing and counting into a general theory of visual perception and spatial attention, as espoused by Marr(1982), Ullman(1984), and Treisman(1988). In particular, it is argued that the rapid apprehension of number in the 1-4 range is parasitic on a preattentive limited capacity mechanism that individuates feature clusters by assigning spatial reference tokens or FINSTs to them(Pylyshyn, 1989). These spatial reference tokens permit the identities of a small number of items to be maintained though their properties and retinal coordinates change, a capability important for directing the attentional focus and coordinating eye and hand movements. If the subitizing process makes use of such preattentive information, then it should not be possible to subitize when spatial attention is required to compute spatial relations, resolve the item as a whole or discern items to be counted from other distractor items. Thus, it was predicted that the slope of the latency function in the 1-4 range should approximate that of the 5+ range if spatial attention is required to perform a particular enumeration task. In contrast, it was predicted that subitizing should be possible when preattentive information could be used to distinguish the items to be counted from one another, or from other distractor items. Therefore, it was predicted that there should be discontinuities in slopes of the latency function between the 1-4 and 5+ range, as shown by deviations from linearity in trend analysis.;Five experiments were performed. In the first, subjects were shown capable of subitizing when the task was to enumerate items of a particular colour though they were not capable of subitizing when the task was to enumerate items that were connected to each other by a contour. This result was expected because spatial attention is presumed necessary to compute the connected relation(Ullman, 1984; Jolicoeur, 1988). The second pair of experiments showed that though subjects can easily subitize when items are defined by groups of contours instead of simple edge points, they cannot easily enumerate such items if they are concentric, as would be predicted given that preattentive grouping processes would cluster all the contours into a unit in this case. The fourth and fifth experiments show that subjects can subitize certain target items in a field of distractors, but only if the property that differentiates targets from distractors is a feature, or a property thought to emerge preattentively. In situations where attention is required to form a unified object description by joining different dimensions (e.g., colour and orientation), or by joining different parts of an item (e.g., an O and a stem to form a Q), subitizing was not apparent. Overall, these experiments suggest that the subitizing process relies on preattentive information

How Missing a Treatment of Mixed Amphetamine Salts Extended Release Affects Performance in Teen Drivers with ADHD

Mixed Amphetamine Salts Extended Release (MAS-XR or Adderall XR®) is a stimulant medication used to control symptoms of ADHD. People occasionally fail to take their medications. The goal of this pilot study was to assess the impact of a single missed medication on driving performance in 14 teen drivers with ADHD mixed type as a function of driving skill. A double-blind placebo control crossover design was used and participants were tested in a driving simulator. On the evening of the first day, baseline measures of driving performance were taken to assess driving skills (on medication). Then on two consecutive days drivers were tested three times a day, one day on medication and the other day off. Results indicated increased collisions and hazard response time off medication, with performance worst on 36 hours post-medication. Participants with the least developed driving skills benefited most from medication. This highlights the importance of consistent medication use in inexperienced teen drivers with ADHD

Manipulating Drive Characteristics to Study the Effects of Mental Load on Older and Younger Drivers

A driving simulator was used to assess performance in younger and older drivers (M ages 18 and 71 years). The impacts of three challenges were assessed: visibility (clear day, fog), traffic density (low, high) and wayfinding (no challenge, drivers challenged to use signs and landmarks to find their destination). Performance was measured in terms of hazard RT, collisions, wayfinding errors (missed or extra turns), and driving speed. The challenge manipulations produced interactive effects and age was a factor in some of these interactions. Older drivers missed more turns in wayfinding but overall they performed as well or better than younger drivers and reduced their speed more to driving challenges

Can Galvanic Vestibular Stimulation Reduce Simulator Adaptation Syndrome?

Electrical stimulation of the vestibular sensory system during virtual environment simulations has been proposed as a method to reduce the incidence of simulator adaptation syndrome (SAS). However, there is limited empirical evidence to support this hypothesis. It is especially important to provide vestibular stimulation in driving simulators because an absence of vestibular cues may alter driver behaviour and reduce vehicle control. This study examined the application of galvanic vestibular stimulation (GVS) as a technique to reduce symptoms of SAS and improve vehicular control in a fixed-based driving simulator. Nineteen participants drove two visually distinct virtual environments (high and low visual cues). In addition, each of these worlds was experienced with and without GVS. Post-drive scores on the Simulator Sickness Questionnaire (SSQ) were used to evaluate the effect of GVS on SAS. In addition, three driving variables were measured to examine driving performance: steering variability, lane departures, and average vehicular speed. GVS application while driving resulted in significant decreases in total SSQ and disorientation symptoms. Greater vehicular control was also observed (as shown by reduced steering variability) when GVS was used in combination with visual cues along the simulated edge of the road. These results support that GVS may be used in fixed-base driving simulators to create vestibular motion cues and reduce SAS

Judging Magnitude: Is there a Common Cognitive System for Different Types ofMagnitude Judgments?

It has been suggested that a common cognitive system is employed in magnitude judgments across multiple modal-ities (Walsh, 2003). To test this theory, we examined whether performance on magnitude judgments of number, surface area,duration, and loudness correlated with each other in both magnitude comparison (e.g., determine which is more), and mag-nitude estimation (e.g., if magnitude 1 value = 100, estimate the value of magnitude 2) tasks. For magnitude comparison,significant correlations were observed between number, surface area, and loudness (but not duration) tasks (percent correctmeasured). Similar results were observed for magnitude estimation (mean absolute percent deviation of value estimates fromcorrect measured). These results are indicative of a common cognitive system for at least some magnitude judgment modalities,and suggest that such a system may play a role not only in more-than/less-than magnitude judgments, but also in the process ofassigning numerical values to magnitudes

Too Close for Comfort: Evaluating a Reward-Based Approach to Increase Drivers\u27 Headway

Tailgating is often implicated as a leading contributor to rear-end collisions but this behaviour is difficult to remediate because drivers are poor at estimating their own headway. Our first goal was to compare novice and fully licensed drivers as they applied existing headway interventions in a driving simulator. Our second goal was to develop an automated, reward-based approach to encourage longer headways. We first compared headway in the driving simulator to previous studies on real-world car following behaviour by asking drivers to (i) achieve what they perceived to be the minimum safe headway or to (ii) employ the common “2 second rule” intervention. We observed a close agreement between the headways achieved in the simulator and those achieved in prior real-world car-following paradigms. We then implemented our headway evaluation system and compared headway across instruction type: (i) minimum safe headway, (ii) “2 second rule”, or (iii) the headway evaluation system. We observed that fully licensed motorists maintained the longest headways while using our system. While drivers reported that the headway evaluation system was easy and appealing to use, they did not foresee continuing to use the device in the future. The current system may be beneficial for driver training applications or to promote situation awareness during the use of automated driver assistance systems such as adaptive cruise control

EFFECT OF DRIVING EXPERIENCE ON CHANGE DETECTION BASED ON TARGET RELEVANCE AND SIZE

Summary: Earlier studies that investigated the effects of driving experience and target safety relevance on change detection have produced conflicting results. Using a flicker change detection task to investigate the effect of driving experience on the ability to detect changes in objects that vary in safety relevance and size, the present study attempted to clarify some controversies by addressing three important methodological issues. The data showed that experienced drivers exhibited more efficient selection strategies than novice drivers and thus may have more spare resources to analyze less relevant objects in the driving environment. Selection strategies for relevant information appear to be sensitive to object size whereas selection of irrelevant information is downgraded comparatively and unaffected by size. Findings are discussed as they relate to theoretical and practical implications

Mind-Wandering and Driving: Comparing Thought Report and Individual Difference Measures

Mind-wandering is a cognitive state in which attention is diverted from the main task and towards more personal thoughts, which can interfere with performance. This study investigated differences in patterns of mind-wandering and driving performance measured during thought-probe versus post-task selfreport conditions, and further differentiated based on individual differences in working memory—as measured by the Operation Span (OSPAN) and Sustained Attention to Response Task (SART). Participants completed two 30-minute drives. Those in the thought-probe condition were asked whether they were thinking of driving; the proportion of trials where they answered “no” was used as the index of mind-wandering. In the post-task condition participants estimated the percentage of time they had mind-wandered during each drive. Speed, steering variability, headway distance, and hazard response time to a lead vehicle braking were also measured. Results showed that the magnitude of mind-wandering captured in the thought-probe condition was greater than in the post-task condition, though hazard response times were also faster despite greater mindwandering reports. Higher OSPAN scores were associated with greater reports of mind-wandering, but only in the post-task condition. Conversely, in the post-task condition those with low SART scores responded slower to hazards than those with high scores; in the thought-probe condition these groups did not differ. Findings indicate a differential impact of report-type on participant experience, emphasizing the need for more covert measures of mind-wandering—e.g., eyetracking or electroencephalography—that provide accurate estimates of task engagement but don’t interfere with task flow

Effect of Alert Presentation Mode and Hazard Direction on Driver Takeover from an Autonomous Vehicle

Autonomous vehicles are becoming increasingly common. Although the level of automation varies between vehicles even the most advanced occasionally require driver input when the driving situation is complex, or the quality of the sensory data is poor. If driver input is needed the system must alert drivers that they will have to take over but these alerts may vary in their effectiveness in prompting rapid driver takeover (time to grip the steering wheel, percentage of appropriate takeover maneuvers) and situational awareness (driver attention to the threat that necessitated take over and understanding for why take over is necessary). In this study, we used a driving simulator operating in autonomous mode to compare 2 alert types (audio-visual, and audio alone) in 3 different takeover scenarios where hazards emerged from the front (a construction zone) or the left or right side (erratic behaviour in another driver: a rogue vehicle heading toward the drivers’ lane). We found that the takeover-time was faster after the audio-visual alert than the audio alert and situation awareness was better. The nature and direction of the hazard also had an effect. Situation awareness was poorer for hazards in front of the vehicle (a looming construction zone) as compared to the left and right of the driver (rogue vehicles heading toward the driver). These findings have important implications for interface design in autonomous vehicles