The (change) blindingly obvious
: investigating fixation behaviour and memory recall during CCTV observation

  • Gemma Graham

Student thesis: Doctoral Thesis


Relatively little is known about the strategies that people use when monitoring and interpreting (criminal) events observed in CCTV footage. Four studies reported in this thesis used a change blindness task to explore: (a) whether instructions and/or event type influence where people attend to during CCTV observation; (b) how factors such as task instructions and central and marginal information influence fixation behaviour during CCTV observation; (c) the effect of change detection on memory recall during CCTV observation; and (d) whether verbalisation, attentional set and/or repeated viewing improve change detection and memory recall rates for CCTV footage. In Experiment one, we found that change detectors fixated on the changing target directly before the change more so than non-detectors. We replicated this finding in Experiment two and additionally found that change detectors, more so than non-detectors, produced significantly more and longer fixations on the change target during the change. The findings from Experiments one and two demonstrated that observers were drawn to a criminal event, more so than a non-criminal event, and that this was especially the case for central rather than marginal events in the footage. We found no evidence that instructions significantly affected gaze behaviour. In Experiment three, we found that change detectors recalled more accurate detail from the CCTV footage compared to the non-detectors, but only once the severity of the crime had increased. Experiment four found improved rates of change detection during CCTV observation when participants were able to repeatedly view the footage. Verbalisation (thinking aloud) however made no difference in terms of change detection and the accuracy of memory recall. These findings may help to inform training courses aimed at instructing people how to optimally attend to CCTV footage.
Date of Award27 Jan 2016
Original languageEnglish
SupervisorLucy Akehurst (Supervisor), James Ost (Supervisor) & Jenny Page (Supervisor)

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