Home > Human Factors history and studies > Miscited psychology concepts – Yerkes-Dodson law

Miscited psychology concepts – Yerkes-Dodson law

As I wanted to write an article about the well-known workload scale I found this interesting story. Usability engineers know the and work with the workload scale. A task performance has its ideal level of workload. Is the workload higher than the ideal level the operator compensates this with application of more resources. If the workload rises more the operator can no longer compensate and gets overloaded, performance declines. In the other direction, if workload is below the ideal level the operator applies additional resources to keep attention to the task. If workload declines further, attention can no longer be kept to a sufficient level and performance declines. Some literature refers for origin of this process to the Yerkes-Dodson law. Let us have a look what they originally did in their study from 1908.

The study conducted by Yerkes and Dodson (original paper) evaluated the relation of stimulus strength and habit formation. Habit formation is seen as a type of learning. The experiment was conducted with a set of mice. The mice’s task was to distinguish between a black and a white box and learn to choose the white box. Selection of the black box resulted in an electrical shock. In the first experiment they presented the electrical stimulus in different strengths and assumed that the rate of failures (choice of the black box) is declining with stimulus strength. But the result revealed a rise of failures in the setting with the highest electrical stimulus. So they mused if this result could be related to the difficulty of the task (discrepancy between black and white box). For proof they conducted two other experiments varying the ease of distinguishability between black and  white box. Indeed the results showed that for the easiest condition failure rate declined with rising electrical stimulus strength.

Beside the miscitation in literature the study itself has its drawbacks: first the sample set of mice used was very small, the difference of black and white box was not measured with a photometer, the task was just comparable simple perceptual one and the analysis of results could be more accurate, they seem mixed over the experimental settings.

In respect of the study one would assume it to be cited in context of stimulus strength and habit formation, or maybe in context of a behavioural learning theory. But teh study has been cited in the literature as base for performance, workload and (physiological) arousal, concepts which where not part of the original experimental setting. A citation in relation to the workload scale ignores their second finding – if the task is easy, failure rate declines with increasing stimulus strength. Following question would be, what happens if the task is even easier? Are those effects applicable to humans with a wider range and flexible learning algorithms? Further it is not clear if a learning induced by a negative stimulus, as applied in the experimental setting, is comparable to higher workload which means also higher stimulus (rate / variance) but that is not negative… there are many questions rising in my head from this experiment. Well, somehow the misciting started…

A good review of the miscitations is this paper from Karl Halvor Teigen, link. Sometimes it is very hard to get hold of the original paper or its hard to read all that many literature of a topic and if something like this theory is so often cited in many psychology books it is a simply belief that it is true.  However, a critical eye is in advantage.

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