Effects of speed–accuracy instructions on oculomotor scanning and target recognition in a simulated baggage X-ray screening task

Abstract

Visual search tasks are often carried out under high levels of time stress. Transportation security screeners, for example, face demands to achieve high levels of accuracy while maintaining rapid passenger throughput. An experiment examined the strategies by which operators regulate visual search performance under such conditions. Observers performed a simulated baggage-screening task under instructions to emphasise either response speed or accuracy. Behavioural measures and eye movements were recorded. Observers made fewer and briefer fixations under emphasise-speed than under emphasise-accuracy instructions. Losses in accuracy were produced by more frequent failures to fixate on targets and a decrease in the detection rate of non-fixated targets. The likelihood with which observers detected a fixated target was similar across speed–accuracy instructions. Results will inform efforts to model visual search in naturalistic tasks, allowing more accurate prediction of response times and error rate and may aid the design of training programmes and other interventions to improve search performance under stress.

Keywords:

• visual search
• attention
• eye movements
• time stress

Acknowledgements

This work was sponsored by a grant to J.S.M. from the Transportation Security Administration. Mandatory disclaimer: Note that as part of the Transportation Security Administration basic research program, the research reported in this paper did not involve Transportation Security Administration screener personnel, screener training materials, and did not take place at and does not represent a true airport screening checkpoint. The views expressed here are those of the authors and do not necessarily reflect those of the organisations with which they are affiliated or their sponsoring agencies. Thanks to Josh Rubinstein at the Transportation Security Lab of the TSA for providing stimulus imagery and to Ron Carbonari and Chris Grant at the University of Illinois for assistance in programming and data collection.