The relation of speeded and unspeeded reasoning with mental speed

Time constraints are commonly applied in the measurement of reasoning ability. We argue that time constraints introduce a spurious mental speed contribution to task performance. As a result, speeded measures of reasoning are conceived as a compound of two functions, namely working memory capacity and mental speed ability. We tested 277 participants with 12 reasoning tasks (six time constrained), and 9 mental speed tasks. Additionally, 90 participants worked on both batteries under timed conditions. The correlations of observed scores as well as factors in a latent variable model show the expected pattern: Mental speed correlates higher with speeded than with unspeeded reasoning measures. Two speeded reasoning tests correlate higher than a speeded and an unspeeded test. The results also indicate that the variance of a speeded reasoning factor can be explained completely by a linear function of unspeeded reasoning and mental speed. It is concluded that the use of speeded reasoning tests is likely to lead to overestimates of the relation between mental speed and reasoning ability. (C) 2002 Elsevier Science Inc. All rights reserved.