Visual search for drowning swimmers: Investigating the impact of lifeguarding experience

How does domain expertise influence dynamic visual search? Previous studies of visual search often use abstract search arrays that are devoid of applied context, with comparatively few studies exploring applied naturalistic and dynamic settings. The current research adds to this literature by examining lifeguard drowning‐detection across two studies using naturalistic, dynamic search tasks. Behavioural responses and eye‐movement data were recorded as participants watched staged video clips and attempted to identify if a swimmer was drowning. The results demonstrate lifeguard superiority in response times to drowning events, compared to non‐lifeguards. No differences between lifeguard and non‐lifeguard eye‐movements were noted however. This suggests that the experiential benefit in response times results from other underlying processes, rather than any scanning benefits. This research highlights the complex nature of naturalistic and dynamic searches, while demonstrating the robust nature of simulated videos in producing experience effects in visual search.     

Great Expectations: Perceptual Challenges of Visual Surveillance in Lifeguarding

The presence of lifeguards on beaches and at pools has the potential to prevent many drowning incidents. This article examines the visual components of the lifeguard's job, discussing some of the major challenges they face during surveillance. These include optical challenges (turbidity and turbulence of the water, light refraction, and glare), scene challenges (elevated set size affecting clutter and perceptual ‘blindnesses’), stimulus challenges (searching for multiple targets that are complex, dynamic, ill‐defined, and rare), and attentional challenges, including but not limited to vigilance issues. The differences between basic laboratory research and the lifeguarding task are explored, with recommendations for future study. Copyright © 2015 John Wiley & Sons, Ltd.     

Gaze behaviour of experienced and novice beach lifeguards – An exploratory in situ study

For lifeguards, recognizing a swimmer in trouble is a key factor in the rescue process. Although reports show that lifeguards outperform non‐lifeguards in their surveillance task, it is unclear to what extent this difference is reflected in gaze behaviour. In the current study, gaze behaviour of nine novice and seven experienced beach lifeguards was recorded for 45 min while they were on active duty. Results showed that fixation duration of experienced lifeguards was longer and more variable than that of novice lifeguards, and that these differences were more pronounced when looking at the task‐relevant region (i.e., swimming zone). Compared to experienced lifeguards, novices were found to be more distracted by the task‐irrelevant regions when there were more people swimming. These findings suggest that experienced lifeguards use a more flexible and task‐related gaze strategy, and that there might be differences in visual information processing between novice and experienced beach lifeguards.     

Why is visual search superior in autism spectrum disorder?

This study investigated the possibility that enhanced memory for rejected distractor locations underlies the superior visual search skills exhibited by individuals with autism spectrum disorder (ASD). We compared the performance of 21 children with ASD and 21 age‐ and IQ‐matched typically developing (TD) children in a standard static search task and a dynamic search task, in which targets and distractors randomly changed locations every 500 ms, precluding the use of memory in search. Children with ASD exhibited overall faster reaction time (RT) relative to TD children, and showed no disruption in search efficiency in the dynamic condition, discounting the possibility that memory for rejected distractors augments their visual search abilities. Analyses of RT x set size functions showed no group differences in slopes but lower intercepts for the ASD group in both static and dynamic search, suggesting that the ASD advantage derived from non‐search processes, such as an enhanced ability to discriminate between targets and distractors at the locus of attention. Eye‐movement analyses revealed that the ASD and TD groups were similar in the number and spatial distribution of fixations across the search array, but that fixation duration was significantly shorter among children with ASD. Lower intercepts in static search were related to increased symptom severity in children with ASD. In summary, ASD search superiority did not derive from differences in the manner in which individuals with ASD deployed their attention while searching, but from anomalously enhanced perception of stimulus features, which was in turn positively associated with autism symptom severity.     

Lifeguards and Physically Risky Prosocial Groups: A comparison based on personality theory

The goal of this study is to explore the personality of experienced professional lifeguards in terms of Eysenck and Eysenck's PEN model of personality and Zuckerman's sensation seeking trait. A sample of 144 male professional lifeguards were contrasted with three different samples: (1) a general population sample; (2) a sample of individuals engaged in physically risky sports; and (3) a sample of prosocial physically risky professionals. It was found that lifeguards resembled most closely the prosocials followed by the sportsmen and finally the general population. The most frequent and largest differences between lifeguards and the comparison groups were found on extraversion, experience seeking, and neuroticism. The implications for lifeguard selection procedures and future research are discussed.     

Intense classification training to increase the detection of drowning swimmers

Lifeguards engage in a continuous process of deciding whether swimmers are in danger or not. The variety of behaviours that distressed swimmers show makes it difficult to impart declarative knowledge to this effect during lifeguard training. As an alternative, we propose a novel training tool that requires novice participants to rapidly categorise 3-s video clips of real-life swimmers as either ‘safe’ or ‘drowning’. A control group also completed a sham intervention, with surfers that may ‘fall’. Due to the complex nature of swimming pools, a scaffolded training approach was employed, which gradually increased the amount of background information over subsequent training rounds. Results demonstrated that the drowning classification training improved responses in a subsequent drowning detection test, compared with the active control-group. The scaffolded approach appeared to prepare participants for processing swimmers in the drowning-detection test. The results provide a foundation for a novel training protocol to improve lifeguard skills.     

Selective attention and search images in pigeons

In a visual search task, pigeons detected targets when pretrial visual cues or blocked trial sequences signaled the target's identity. Sequential priming was robust over a wide range of intertrial intervals, but visual priming was unstable when the delay between cue offset and display onset was varied. Larger target set sizes enhanced sequential, but not visual, priming. Sequential priming did not depend on display size over the range of relatively large displays used. However, ambiguously cued targets in small displays were detected more quickly than primed targets in large displays. These findings suggest that naturalistic selection biases, or "search images," may be attributable to sequential priming and that the common attentional mechanism has moderately selective properties.     

The development of organized visual search

Visual search plays an important role in guiding behavior. Children have more difficulty performing conjunction search tasks than adults. The present research evaluates whether developmental differences in children's ability to organize serial visual search (i.e., search organization skills) contribute to performance limitations in a typical conjunction search task. We evaluated 134 children between the ages of 2 and 17 on separate tasks measuring search for targets defined by a conjunction of features or by distinct features. Our results demonstrated that children organize their visual search better as they get older. As children's skills at organizing visual search improve they become more accurate at locating targets with conjunction of features amongst distractors, but not for targets with distinct features. Developmental limitations in children's abilities to organize their visual search of the environment are an important component of poor conjunction search in young children. In addition, our findings provide preliminary evidence that, like other visuospatial tasks, exposure to reading may influence children's spatial orientation to the visual environment when performing a visual search.     

Allocation of attention in texture segregation, visual search, and location-precuing paradigms

Is there a common mechanism (or set of mechanisms) that controls the allocation of spatial attention in texture segregation, visual search, and location-precuing tasks? This question was addressed by comparing data from our previous research on location-cuing and search tasks with data from a new set of experiments on texture segregation, in which a common set of stimuli was used across the three paradigms. However, when we ranked the scores for the targets on texture segregation speed, search rate, and improvement due to precuing effects, agreement between these measures was less than perfect. Further analyses of these results led to the following conclusions: (a) speed of texture segregation is affected by perceptual aspects of the display other than the attentional salience of a particular target; (b) visual search rate and the size of precuing effects are strongly related over most of the set of targets we used; and (c) some cases in which search rate was not consistent with size of precue effects may be related to the presence of nearby distractors in the search task.     

Enhanced visual performance in obsessive compulsive personality disorder

Visual performance is considered as commanding modality in human perception. We tested whether Obsessive–compulsive personality disorder (OCPD) people do differently in visual performance tasks than people without OCPD. One hundred ten students of Ferdowsi University of Mashhad and non‐student participants were tested by Structured Clinical Interview for DSM‐IV Axis II Personality Disorders (SCID‐II), among whom 18 (mean age = 29.55; SD = 5.26; 84% female) met the criteria for OCPD classification; controls were 20 persons (mean age = 27.85; SD = 5.26; female = 84%), who did not met the OCPD criteria. Both groups were tested on a modified Flicker task for two dimensions of visual performance (i.e., visual acuity: detecting the location of change, complexity, and size; and visual contrast sensitivity). The OCPD group had responded more accurately on pairs related to size, complexity, and contrast, but spent more time to detect a change on pairs related to complexity and contrast. The OCPD individuals seem to have more accurate visual performance than non‐OCPD controls. The findings support the relationship between personality characteristics and visual performance within the framework of top‐down processing model.     

Comparison of the Effects of Formal and Informal Accountability on the Correct Performance of a Lifeguard Rescue

We compared instructional strategies used to train lifeguards. Fifteen undergraduates participated in the study during their twice weekly 90 minute lifeguard classes. A checklist of 15 steps was used to define correct performance of a lifeguard (water) rescue. The dependent variable was the percentage of steps completed correctly. Data were collected from videotapes of 32 sessions. A multi-treatment reversal design was used to assess the efficacy of typical peer instruction, a triad where students verbally supported one another, a triad where members used a checklist to prompt correct performance, and a instructor-mediated condition where for each 90% or better correct performance the participant received a bonus grade point. The significance of the rescue was not enough to produce competent performance, neither was peer support, nor peer-mediated instruction using a checklist, but all participants achieved 90% correct performance or better during the instructor-mediated condition. Our results suggest that the instructor-mediated condition is considerably more effective than informal accountability.     

Visual search in a multi-element asynchronous dynamic (MAD) world

In visual search tasks participants search for a target among distractors in strictly controlled displays. We show that visual search principles observed in these tasks do not necessarily apply in more ecologically valid search conditions, using dynamic and complex displays. A multi-element asynchronous dynamic (MAD) visual search was developed in which the stimuli could either be moving, stationary, and/or changing in luminance. The set sizes were high and participants did not know the specific target template. Experiments 1 through 4 showed that, contrary to previous studies, search for moving items was less efficient than search for static items and targets were missed a high percentage of the time. However, error rates were reduced when participants knew the exact target template (Experiment 5) and the difference in search efficiency for moving and stationary targets disappeared when lower set sizes were used (Experiment 6). In all experiments there was no benefit to finding targets defined by a luminance change. The data show that visual search principles previously shown in the literature do not apply to these more complex and "realistically" driven displays.     

Awareness of the continuously visible: information acquisition during preview

What can we learn about a scene while we stare at it, but before we know what we will be looking for? Three experiments were performed to investigate whether previewing a search array prior to knowing the target allows search to operate more quickly (lower reaction time [RT]), more efficiently (reduced set size slope), and/or by consulting abstract mental representations. Experiment 1 compared RTs for previewed and nonpreviewed arrays, some of which were highly degraded with visual noise. Preview reduced RTs for the noisy displays but did not affect search efficiency. Limited interactions of visual quality and preview suggested that prior exposure allowed the extraction and maintenance of about three abstract identities. If the target was one of those items, the observer responded without searching; if not, the observer searched the remaining items as if there had been no preview. Experiment 2 replicated these findings with less extreme noise. In Experiment 3, subjects previewed 0-6 items of a 12-item display. RTs decreased linearly as the number of previewed items increased from 0 to 3 and then reached a plateau, confirming that the capacity of the representation was about 3 items. Implications for visual awareness are discussed.     

Effects of speed and accuracy instructions on performance in a visual search task by children with good or poor attention

Children rated by teachers as having good or poor attention ability carried out a visual search task in which they were required to find a series of targets in a complex display. Different groups were told to concentrate on either speed or accuracy. Previous studies using this task have consistently shown that children rated as having poor attention make more errors (false alarms to non‐targets in the display), but do not differ in the time to make a correct response; this result was replicated. Though the instructions produced wide differences in speed and error rates in the expected directions, these differences were similar in both attention groups and the differences in error rates between the two groups remained unchanged. It is suggested that these findings are not compatible with the view that children with poor attention make errors primarily due to fast impulsive responding, nor with an explanation in terms of slower processing of the input by such children. An alternative explanation of the high error rates in such children is offered in terms of weak executive function resulting in poor ability to inhibit false alarms to non‐targets.     

Attentional Capture by Emotional Stimuli: Manipulation of Emotional Valence by the Sample Pre‐rating Method

Eye movements directed at emotional and neutral pictures were investigated. Participants were instructed to fixate on a target and avoid looking at a non‐target. Results of trials consisting of emotional and neutral pictures were analyzed based on participants’ evaluations of the stimuli before the experiment. Results indicated that the number and duration of fixations were larger and longer for targets than for non‐targets. Further, the probability of first fixation was less for neutral targets than for emotional targets. This suggests that unpleasant pictures capture visual attention and that the attentional orienting is subject to automatic response. The possibility that top‐down processes of visual attention may be involved in attentional capture was also discussed.     

Visual search for global/local stimulus features in humans and baboons

Fagot and Deruelle (1997) demonstrated that, when tested with identical visual stimuli, baboons exhibit an advantage in processing local features, whereas humans show the “global precedence” effect initially reported by Navon (1977). In the present experiments, we investigated the cause of this species difference. Humans and baboons performed a visual search task in which the target differed from the distractors at either the global or the local level. Humans responded more quickly to global than to local targets, whereas baboons did the opposite (Experiment 1). Human response times (RTs) were independent of display size, for both local and global processing. Baboon RTs increased linearly with display size, more so for global than for local processing. The search slope for baboons disappeared for continuous targets (Experiment 2). That effect was not due to variations in stimulus luminance (Experiment 3). Finally, variations in stimulus density affected global search slopes in baboons but not in humans (Experiment 4). Overall, results suggest that perceptual grouping operations involved during the processing of hierarchical stimuli are attention demanding for baboons, but not for humans.     

Toddlers with Autism Spectrum Disorder are more successful at visual search than typically developing toddlers

Plaisted, O'Riordan and colleagues (Plaisted, O'Riordan & Baron-Cohen, 1998; O'Riordan, 2004) showed that school-age children and adults with Autism Spectrum Disorder (ASD) are faster at finding targets in certain types of visual search tasks than typical controls. Currently though, there is very little known about the visual search skills of very young children (1-3-year-olds) - either typically developing or with ASD. We used an eye-tracker to measure looking behavior, providing fine-grained measures of visual search in 2.5-year-old toddlers with and without ASD (this representing the age by which many children may first receive a diagnosis of ASD). Importantly, our paradigm required no verbal instructions or feedback, making the task appropriate for toddlers who are pre- or nonverbal. We found that toddlers with ASD were more successful at finding the target than typically developing, age-matched controls. Further, our paradigm allowed us to estimate the number of items scrutinized per trial, revealing that for large set size conjunctive search, toddlers with ASD scrutinized as many as twice the number of items as typically developing toddlers, in the same amount of time.     

Monitoring eye movements while searching for affective faces

A single experiment is reported in which we provide a novel analysis of eye movements during visual search to disentangle the contributions of unattended guidance and focal target processing to visual search performance. This technique is used to examine the controversial claim that unattended affective faces can guide attention during search. Results indicated that facial expression influences how efficiently the target was fixated for the first time as a function of set size. However, affective faces did not influence how efficiently the target was identified as a function of set size after it was first fixated. These findings suggest that, in the present context, facial expression can influence search before the target is attended and that the present measures are able to distinguish between the guidance of attention by targets and the processing of targets within the focus of attention.     

Saved by a log: how do humans perform hybrid visual and memory search?

Could you find 1 of your 1,000 Facebook friends in a crowd of 100? Even at a rate of 25 ms per comparison, determining that no friends were in the crowd would take more than 40 min if memory and visual search interacted linearly. In the experiment reported here, observers memorized pictures of 1 to 100 targets and then searched for any of these targets in visual displays of 1 to 16 objects. Response times varied linearly with visual set size but logarithmically with memory set size. Data from memory set sizes of 1 through 16 accurately predicted response times for different observers holding 100 objects in memory. The results would be consistent with a binary coding of visual objects in memory and are relevant to applied searches in which experts look for any of many items of interest (e.g., a radiologist running through a mental checklist of what might be wrong in a car-crash victim or an airport screener looking for any of a list of prohibited items in a carry-on bag).     

Visual search in children and adults: Top-down and bottom-up mechanisms

Three experiments investigated visual search for targets that differed from distractors in colour, size, or orientation. In one condition the target was defined by a conjunction of these features, while in the other condition the target was the odd one out. In all experiments, 6–7- and 9–10-year-old children were compared with young adults. Experiment 1 showed that children's search differed from adults' search in two ways. In conjunction searches children searched more slowly and took longer to reject trials when no target was present. In the odd-one-out experiments, 6–7-year-old children were slower to respond to size targets than to orientation targets, and slower for orientation targets than for colour targets. Both the other groups showed no difference in their rate of responding to colour and orientation. Experiments 2 and 3 highlighted that these results were not a function of either differential density across set sizes (Experiment 2) or discriminability of orientation and colour (Experiment 3). Across all three experiments, the results of both conjunction and odd-one-out searches highlighted a development in visual search from middle to late childhood.