Citation

Page J, Bates V, Long G, Dawes P, Tipton MJ. Ophthalmic. Physiol. Opt. 2011; 31(3): 216-224.

Affiliation

Department of Sport and Exercise Sciences, University of Portsmouth, Portsmouth, UK Royal National Lifeboat Institution, Poole, UK.

Copyright

(Copyright © 2011, John Wiley and Sons)

DOI

10.1111/j.1475-1313.2011.00824.x

PMID

21410495

Abstract

Purpose:  Lifeguard surveillance is critical to any water safety program. This study determined the rates of detection of a 'drowning' individual by beach lifeguards, and whether scanning patterns differed between groups of lifeguards (experienced/less experienced, male/females, surf/non-surf). It was hypothesized that (1) Experienced lifeguards would perform better and produce less fixations of longer duration than inexperienced; (2) A greater detection rate would be seen in a 'biased' compared to a 'non-biased' condition; (3) There would be no differences between the surf compared to non-surf lifeguards, and male compared to female lifeguards with regard to scanning patterns or detection rates. Method:  A mobile eye tracker was worn by each lifeguard (n = 69, 52 males, 17 females) as they watched 12 min of animated beach footage projected onto a screen in two conditions: a. 'Non-biased' (uniform scene). b. 'Biased' (uniform scene with presumed 'rip' on right side of screen). The lifeguards were informed that at any point during the 12 min a person may or may not disappear and to highlight if and where, a person disappeared. Unknown to the participants, a person always disappeared after 10 min at the same position within, but not between, conditions. Data were analysed using anova, t-tests and binary logistic regression. Results:  Experienced lifeguards were five times (p < 0.05) more likely to detect the drowning individual than inexperienced lifeguards. There were no significant differences between the visual search patterns of the groups between 2 and 10 min. The detection rates averaged 16% in the non-biased condition and 29% in biased conditions (p < 0.1), probably because lifeguards searched more on the right of the water. Furthermore, 40% (biased) and 42% (non-biased) did not detect the person disappearing, even though they fixated in the correct location in the 3.5 s before the person completely disappeared. This suggests that some lifeguards may have fixated on, but not processed, relevant visual data ('looked at but not seen'). 25% (biased) and 36% (non-biased) of the lifeguards did not fixate in the location of the person disappearing, but were able to identify their disappearance. Conclusions:  Visual search patterns used by lifeguards can be altered by instruction and detection rates improve as a consequence. Peripheral vision is used effectively by some lifeguards, but cue extraction may be problematic for others.

Language: en