Speed-Accuracy Trade-Offs and General Systems Performance Theory: Novel Application to Fitts’ Law and Beyond

Speed-accuracy trade-offs have long been of interest in human performance. General Systems Performance Theory (GSPT) was motivated by human performance measurement and modeling needs. It has subsequently been applied in those and other areas. In GSPT, all system performance attributes are modeled using a resource construct. Systems are characterized by multi-dimensional performance capacity envelopes (PCEs). The systems of interest here are considered to possess limited speed and accuracy performance resources defining a two-dimensional PCE. When considering human movement, relevance to Fitts’ law was conjectured. In multiple Fitts’ paradigm tasks, we found a near-perfect correlation between Index of Performance (IP) and PCE area. An almost exact prediction was obtained when scaled by Fitts\u27 index of task difficulty (ID). While the well-known Fitts’ law equation does not contain accuracy explicitly, the GSPT-derived expression (CPS-A= ID • Speed • Accuracy) contains both speed (motions/s) and accuracy (hits/attempts). Concepts are applicable beyond human movement; e.g., to visual, auditory, or other information processing types

An evaluation of standing-induced lower leg edema as a function of floor surace

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Includes bibliographical references.Issued also on microfiche from Lange Micrographics.Jobs requiring workers to stand for prolonged periods are common in industry. People whose work involves standing frequently complain of discomfort, particularly in the legs. A study was conducted to determine the amount of edema that occurs in the lower leg and the level of discomfort people experience as a result of standing on six industrial floor surfaces. Twelve (six female, six male) healthy, college-aged subjects stood for 16 hours (four experimental periods of four hours each)on each of the surfaces. The surfaces used included: two brands of anti-fatigue mat, three types of industrial grating, and concrete. Using water volume displacement, edema of three segments of the right leg (ankle-and-below, calf-and-below, and knee-and-below) was measured for each experiment period. The greatest edema was found in the knee-and-below segment followed by the calf-and-below and ankle-and-below segments. The floor surface (Pr>F=0.110) and the number of weeks the subjects participated in the study (Pr>F=0.140) had no significant effect on the edema of any of the segments. No significant interactions were noted. In the subjective discomfort analysis, significance was found due to gender (Prob=0.033). For the body regions of the legs and back, females generally reported experiencing greater discomfort than males as a result of standing. No significance was found due to floor surface (Prob=0.324) or the number of weeks the subjects participated in the study (Prob=0.116). The subjects ranked the two anti-fatigue mats as being the most preferable of the six surfaces