Date Published: January 21, 2014
Publisher: Public Library of Science
Author(s): Erika Näsholm, Sarah Rohlfing, James D. Sauer, Philip Allen.
Closed Circuit Television (CCTV) operators are responsible for maintaining security in various applied settings. However, research has largely ignored human factors that may contribute to CCTV operator error. One important source of error is inattentional blindness – the failure to detect unexpected but clearly visible stimuli when attending to a scene. We compared inattentional blindness rates for experienced (84 infantry personnel) and naïve (87 civilians) operators in a CCTV monitoring task. The task-relevance of the unexpected stimulus and the length of the monitoring period were manipulated between participants. Inattentional blindness rates were measured using typical post-event questionnaires, and participants’ real-time descriptions of the monitored event. Based on the post-event measure, 66% of the participants failed to detect salient, ongoing stimuli appearing in the spatial field of their attentional focus. The unexpected task-irrelevant stimulus was significantly more likely to go undetected (79%) than the unexpected task-relevant stimulus (55%). Prior task experience did not inoculate operators against inattentional blindness effects. Participants’ real-time descriptions revealed similar patterns, ruling out inattentional amnesia accounts.
Reliance on Closed Circuit Television (CCTV) surveillance is increasing –. Surveillance operators are responsible for maintaining the security of critical infrastructure (e.g., airports and government buildings) and public spaces (e.g., streets and shopping malls). Research on CCTV has typically evaluated technological effectiveness (e.g., image quality; see ), operators’ ability to match CCTV images of culprits with live or photographed suspects (e.g., ), or the impact of CCTV prevalence on crime rates and public perceptions of security (e.g., ). While the importance of human factors in CCTV operating has been identified , , research investigating human performance in the CCTV monitoring context is scarce , . This is surprising as ineffective monitoring can have serious consequences. The failure to detect criminal targets or events and intervene appropriately not only facilitates criminal activity but also fosters negative public perceptions of and apathy towards security measures. We investigated the effects of three factors (i.e., inattentional blindness, sustained attention and prior task experience) on CCTV monitoring performance.
We demonstrated inattentional blindness for naïve and experienced CCTV operators using both real-time verbalization measures and post-event recall measures of detection. Further, the effect persisted even when more lenient criteria for detection – representing a more conservative test of inattentional blindness – were applied. Inattentional blindness rates were lower (detection rates were higher) when the unexpected stimulus was relevant to the primary monitoring task than when the unexpected stimulus was irrelevant to the primary monitoring task. However, contrary to expectations, inattentional blindness rates did not increase when the task required longer periods of monitoring. Importantly, both experienced and naïve operators demonstrated inattentional blindness. Detection rates based on the post-event questionnaire were higher than those based on the transcripts, supporting previous work (e.g., , ) suggesting that inattentional blindness cannot be attributed to memory failure (cf. inattentional amnesia, ). These findings extend previous research (e.g., ) to demonstrate that inattentional blindness is a robust phenomenon in applied monitoring contexts, and that observer expectations influence detection rates. First, we discuss the effects of our manipulations on inattentional blindness rates, and relevant theoretical and applied implications. Second, we explore applied and methodological issues arising from data gathered using multiple methods for measuring inattentional blindness.