CHEX (Change History EXplicit)

Users monitor situations to identify significant changes and respond to them quickly. Yet detecting changes is surprisingly difficult. Human attention is notoriously "leaky" and interruptions due to multi-tasking or other distractions exacerbate the problem. Current display technologies provide surprisingly little support for detecting and identifying significant situation changes and therefore do not provide much support for the recovery of situation awareness following interruptions. Instead, situation displays typically only represent the current situation, which forces users to rely on their own ability to extract changes by cognitively integrating events over time. Dangerously, users over-estimate their change detection ability.

Sustained situation awareness can be greatly improved by augmenting users' abilities with automated situation change detection. But the design of the presentation of change information turns out to be crucial and hinges on the issue of how to alert and inform the user effectively without distracting from other important on-going tasks. PSE has developed a novel display concept called CHEX (Change History EXplicit). CHEX augments the human attentional system with a set of intelligent change detectors whose output is logged in a re-configurable table format that is linked back to the situation display. CHEX is extremely effective both for maintaining situation awareness when monitoring a situation as well as when recovering situation awareness following an interruption. CHEX improved response times as much as 80% and the rate of misses dropped to zero.

An intuitively appealing solution to the problem of situation awareness recovery might appear to be Instant Replay. With replay, users can see interrupted periods at high speed to quickly perceive changes. Instant Replay's appeal seems to rest on its familiarity and realistic re-presentation of the temporal sequence of the interrupted situation. But Instant Replay throws users back on their far from perfect natural change detection ability and our research has shown it to provide worse than no support at all.

The CHEX concept is applicable to a wide range of complex monitoring tasks such as air traffic control, missile defense, anti-submarine warfare, meteorology, oceanography, tactical situation awareness, intelligence, surveillance, and reconnaissance.