Running head : QUALITATIVE INDIVIDUAL DIFFERENCES 1 Beyond Means : Are There Stable Qualitative Individual Differences in Cognition ?

Abstract

In this paper we propose a new set of questions that focus on the direction of effects. In almost all studies the direction is important. For example, in a Stroop task it implies one theoretical explanation if incongruent words are slowed relative to congruent ones, but a completely different theoretical explanation if congruent words are slowed down relative to incongruent ones. We ask a ‘does everybody’ question, such as, ‘does every individual show a Stroop effect?’ Or, ‘does every individual respond faster to loud as soft tones?’ If all individuals truly have effects in the same direction that implicate a common theory we term the differences among them as quantitative individual differences. Conversely, if all individuals truly have effects in contrasting directions that implicate different theories we term the differences among them as qualitative individual differences. Here, we provide a users-guide to the question of whether individual differences are qualitative or quantitative. We discuss new software for assessment, and, more importantly, how the question impacts theory development in cognitive science. Our hope is that this mode of analysis is a productive tool in researchers’ toolkits.