In the modern landscape, cognitive abilities—perception, language, problem solving, memory among others—are considered information-processing skills. Research questions center on how structure in the environment is mentally represented, manipulated, combined, stored, retrieved, and evaluated. And one of the key questions is how people might differ in these activities.
We develop models of how people might differ in information-processing abilities. Our current main focus is on the distinction between between quantitative and qualitative individual differences. Qualitative individual differences refer to variation in how people represent or process information. For example, it is widely thought that numbers are mentally represented in an analog fashion much like length. Yet, suppose some people represent numbers as propositions without explicitly encoding a number-line representation. That difference would be qualitative. Quantitative individual differences refer to differences not in representation or encoding, but just in degree—everyone has an analog representation but some people have more resolution than others. A task that has only quantitative differences is detecting soft tones in noise. The louder the tone, the quicker the response. Although people may vary in just how much faster they respond to loud than soft tones, there is nobody that reverses this ordering and responds quicker to soft than loud tones. In this sense the differences are quantitative rather than qualitative.
We have been focusing on tasks with qualitative differences. If differences are qualitative, then rich theoretical interpretations with multiple representations, processes, or strategies may be warranted. Moreover, the focus shifts to who is in which qualitative category, and what are the correlates of this category membership. Currently, we are using the quantitative-vs.-qualitative distinction to explore tasks requiring cognitive control. The main question is whether there is a unified concept of cognitive control that extends across all tasks requiring attention.