Fatigue, oscillation, and blocks.

Abstract

A study of the successive reaction times in the continuous performance of a homogeneous mental task discloses pauses or lengthened reaction times which appear at more or less regular intervals. In such simple tasks as color-naming, form-naming, code substitution, addition, naming opposites, and the like, these pauses occur on the average about three times a minute. In a previous article, (i), the author has described these pauses under the title 'blocks,' and has pointed out that they decrease in frequency and size with practice, increase with fatigue, and vary from individual to individual, being most frequent and longest in slow workers and vice versa. For purposes of quantitative study, blocks were arbitrarily defined as pauses equivalent in length to the time of two or more average responses. This definition is not entirely arbitrary, however, for if a given subject's reaction times are plotted in the form of a frequency polygon, in which the base represents reaction time in eighths of a second, it is found that two distinct modes appear, one of which is due to the central tendency in normal reaction times, while the other shows the central tendency of the blocks. The block mode appears at a point representing approximately double the normal reaction time mode.The relative periodicity of these blocks suggested an interpretation in terms of some hypothetical periodicity in nervous energy or capacity. A number of studies by different authors at widely different times have given evidence of periodic fluctuations in mental efficiency; among which are fluctuations in the threshold for apprehension of minimal stimuli, fluctuations in the focus of attention, fluctuations in performance level, such as those recently described in ' 563

Mental Set and Mental Shift Revisited

“…A second possible source of interference on the pure lists derives from the work of Bills and Robinson (Bills, 1931(Bills, , 1935a(Bills, , 1935bRobinson and Bills, 1926), who suggested that homogeneous (pure) lists are more likely to suffer 'mental blocks.' They defined a mental block as a temporary stop in a continuous task and, using tasks such as continuously writing or saying 'ababab...' or 'abcdefabcdef...,' found that as task homogeneity and response competition increased, so did the tendency toward more frequent and longer mental blocks.…”

Inhibition in Prolonged Work Tasks

“…This led to the formulation of the so-called Poisson-Erlang model. The notion of intermediate periods of distraction has already been suggested by many authors, such as Peak and Boring (1926), Bills (1931, 1935, and Berger (1982). The Poisson-Erlang model accounts for short-term variation in the latencies, but not for any long-term trend effect.…”

Fatigue Stressors in Simulated Long-Duration Flight. Effects on Performance, Information Processing, Subjective Fatigue, and Physiological Cost

“…This phenomenon appears to have been recognized first by Woodworth and Wells (232), and has subsequently been referred to as "fluctuations" or "oscillations" in behavior (Entwistle: 66; FlUgel: 74; and Philpott: 168). Bills (22,23,27) has made a thorough investigation of this effect during short-term fatigue and has referred to it as "blocking. "…”