A Working Memory Model of a Common Procedural Error

Abstract

Systematic errors In performance are an important aspect of human behavior that have not received adequate explanation. One such systematic error is termed postcompletion error; a typical example is leaving one's card In the automatic teller after withdrawing cash. This type of error seems to occur when people have an extra step to perform in a procedure after the main goal has been satisfied. The fact that people frequently make this type of error, but do not make this error every time, may best be explained by considering the working memory load at the time the step is to be performed: The error is made when the load on working memory is high, but will not be made when the load is low. A model of performance In the task was constructed using Just and Carpenter's (1992) CAPS that predicted that high working memory load should be associated with postcompletion errors. Two experiments confirmed that such errors can be produced in a laboratory as well as a naturalistic setting, and that the conditions under which the CAPS model makes the error are consistent with the conditions under which the errors occur in the laboratory.

Tower of Hanoi: Evidence for the cost of goal retrieval.

“…Interestingly, Byrne and Bovair (1997) find that what they call postcompletion errors (e.g., leaving a card in an ATM machine) occur when people forget a goal and the problem display does not support reconstructing the goal. Thus, people fail to adequately rehearse and suffer retrieval errors even in situations where the external display does not support goal memory.…”

The Design with Intent Method: A design tool for influencing user behaviour

“…This was primarily because the cash was dispensed before the card was returned (i.e. a different sequence for Plan 3 in the HTA of Figure 3), leading to a postcompletion error-"errors such as leaving the original document behind in a photocopier... [or] forgetting to replace the gas cap after filling the tank" (Byrne & Bovair 1997). Postcompletion error is an error of omission (Matthews et al 2000); the user's main goal (Plan 0 in Figure 3) of getting cash was completed so the further "hanging postcompletion action" (Chung & Byrne 2008) of retrieving the card was easily forgotten.…”

Interruption of the Tower of London task: Support for a goal-activation approach.

“…This representation provides a convenient parallel to the processes of goal decomposition in means-ends analysis whereby goals are hierarchically broken down into smaller, more manageable subgoals, with each, upon completion, pointing back to a preceding parent goal. Experience tells us, however, that goal memory is rarely this precise: Action slips occur if the correct goal is not retrieved at the correct time (Reason, 1990), or goals may be forgotten altogether in the absence of a cue appropriate to prime retrieval (Byrne & Bovair, 1997). Although it does not challenge other aspects of the ACT-R architecture, recent research contests ACT-R's assumption of a goal stack and instead suggests that goal memory may be subject to the same processes that govern declarative memory.…”