Effects of format complexity on user performance and facial electromyographic activity: II

Abstract

Twenty-four experienced male and female computer users evaluated a 16-row database record that was presented successively 256 times on a video display terminal (VDT) screen. Each evaluation required the decision that the data adjacent to a target label field was identical to or different from a target data item. Target label fields and data items were presented successively and singly prior to the presentation of the database record to be evaluated. Label fields and data items were controlled for word familiarity. The database record had four configurations (i.e., formats) that differed in terms of bit-level complexity, which also produced differences in local density. Decision times (i.e., latencies) were assessed in a repeated-measures experimental design, and, concurrently, electromyographic (EMG) activity was recorded for the masseter (jaw) and corrugator supercilii (eyebrow) muscles. The results showed that decision times differed among the four formats, but bit-level complexity was found to be unrelated to decision times. Masseter EMG activity differed between presentations of the formats and presentations of the target label fields and data items. Corrugator supercilii EMG activity differed between an “eyes open” baseline interval and presentations of the formats and target label fields and data items. These data show that different configurations of information can affect user response times and that masseter and corrugator supercilii EMG responses are differentially sensitive to various components of a task. The results, however, do not support the conclusion that bit-level complexity of a database record, displayed on a VDT screen, will predict user performance or facial EMG activity, although the latter data are promising as on-line indices of affect-laden information processing. Local density of information and estimates of eye movement distances may best predict user performance.