Positive post-disaster images: A daydream machine?

This study explores the impact of post-earthquake images inserted in a vigilance task, in terms of performance, self-reports of task-focus, and cerebral activity using functional near-infrared spectroscopy (fNIRS). Vigilance tasks present a sequence of stimuli in which only a few are pre-designated critical or target stimuli requiring an overt response from the participant. Seventy-one residents participated (51 women, 20 men) by taking part in a vigilance task with task-irrelevant images inserted in the sequence. There were three conditions consisting positive (emotive inducing), negative (emotive inducing), and control (devoid of meaning) images embedded in the vigilance task to assess possible impacts on vigilance performance. The images were obtained through crowdsourcing and represented parts of the city 3-4 years post-earthquake. Task performance was assessed with signal detection theory metrics of sensitivity A' and bias β''. This enables the separation of an individual's ability to accurately discriminate critical signals from non-critical stimuli (sensitivity) and shifts in their willingness to respond to any stimuli whether critical or not (bias). Individuals viewing the positive images, relating to progress, rebuild, or aesthetic aspects within the city, had a more conservative response bias (they responded less to both rare critical and distractor stimuli) than those in the other conditions. These individuals also reported lower task-focus, as would be expected. However, contrary to expectations, indicators of cerebral activity (fNIRS) did not differ significantly between the experimental groups. These results, when combined, suggest that mind wandering events may be being generated when exposed to positive post-earthquake images.