Human Error as an Emergent Property of Action Selection and Task Place-Holding.

OBJECTIVE: A computational process model could explain how the dynamic interaction of human cognitive mechanisms produces each of multiple error types. BACKGROUND: With increasing capability and complexity of technological systems, the potential severity of consequences of human error is magnified. Interruption greatly increases people's error rates, as does the presence of other information to maintain in an active state. METHOD: The model executed as a software-instantiated Monte Carlo simulation. It drew on theoretical constructs such as associative spreading activation for prospective memory, explicit rehearsal strategies as a deliberate cognitive operation to aid retrospective memory, and decay. RESULTS: The model replicated the 30% effect of interruptions on postcompletion error in Ratwani and Trafton's Stock Trader task, the 45% interaction effect on postcompletion error of working memory capacity and working memory load from Byrne and Bovair's Phaser Task, as well as the 5% perseveration and 3% omission effects of interruption from the UNRAVEL Task. CONCLUSION: Error classes including perseveration, omission, and postcompletion error fall naturally out of the theory. APPLICATION: The model explains post-interruption error in terms of task state representation and priming for recall of subsequent steps. Its performance suggests that task environments providing more cues to current task state will mitigate error caused by interruption. For example, interfaces could provide labeled progress indicators or facilities for operators to quickly write notes about their task states when interrupted.

Spatial reasoning with multiple intrinsic frames of reference.

Establishing and updating spatial relationships between objects in the environment is vital to maintaining situation awareness and supporting many socio-spatial tasks. In a complex environment, people often need to utilize multiple reference systems that are intrinsic to different objects (intrinsic frame of reference, IFOR), but these IFORs may conflict with each other in one or more ways. Current spatial cognition theories do not adequately address how people handle multi-IFOR reasoning problems. Two experiments manipulated relative orientations of two task-relevant objects with intrinsic axes of orientation as well as their relative task salience. Response times (RTs) decreased with increasing salience of the targeted IFOR. In addition, RTs increased as a consequence of intrinsic orientation conflict, but not by amount of orientation difference. The results suggest that people encounter difficulties when they have to process two conflicting IFOR representations, and that they seem to prioritize processing of each IFOR by salience.

Planning in sentence production: evidence for the phrase as a default planning scope.

Controversy remains as to the scope of advanced planning in language production. Smith and Wheeldon (1999) found significantly longer onset latencies when subjects described moving-picture displays by producing sentences beginning with a complex noun phrase than for matched sentences beginning with a simple noun phrase. While these findings are consistent with a phrasal scope of planning, they might also be explained on the basis of: (1) greater retrieval fluency for the second content word in the simple initial noun phrase sentences and (2) visual grouping factors. In Experiments 1 and 2, retrieval fluency for the second content word was equated for the complex and simple initial noun phrase conditions. Experiments 3 and 4 addressed the visual grouping hypothesis by using stationary displays and by comparing onset latencies for the same display for sentence and list productions. Longer onset latencies for the sentences beginning with a complex noun phrase were obtained in all experiments, supporting the phrasal scope of planning hypothesis. The results indicate that in speech, as in other motor production domains, planning occurs beyond the minimal production unit.