Spontaneous and imposed speed of cognitive test responses

Based on data from a cognitive test presented in a condition with time constraints per item and a condition without time constraints, the effect of speed on accuracy is investigated. First, if the effect of imposed speed on accuracy is negative it can be explained by the speed–accuracy trade-off, and if it can be captured through the corresponding latent variables, then measurement invariance applies between a condition with and a condition without time constraints. The results do show a negative effect and a lack of measurement invariance. Second, the conditional accuracy function (CAF) is investigated in both conditions, with and without time constraints. The CAF shows an (item-dependent) negative conditional dependence between response time and response accuracy and thus a positive relationship between speed and accuracy, which implies that faster responses are more accurate. In sum, there seem to be two kinds of speed effects: a speed–accuracy trade-off effect induced by imposed speed and an opposite CAF effect associated with speed within conditions. The second effect is interpreted as stemming from a within-person variation of the cognitive capacity during the test which simultaneously favours or disfavours speed and accuracy.