Humans deploy diverse strategies in learning same–different discrimination tasks

Prior research suggests that variability discrimination is basic to same–different conceptualization (Young and Wasserman, 2001). In that research, people were trained with 16-item arrays; this training might have encouraged people to use perceptual variability to solve the task. Here, two groups of participants were trained with either 2- or 16-item Same and Different arrays (Groups 2 and 16, respectively). Participants had to learn which of two arbitrary responses was correct for the arrays without being told about the “sameness” or “differentness” of the stimuli. Surprisingly, 52% of participants in Group 2 did not learn the discrimination compared to only 21% of participants in Group 16; also, learners in Group 16 reached higher accuracy levels sooner and their choice responding was faster than learners in Group 2. A large disparity in the variability (measured by entropy) between the Same and Different arrays evidently helped participants to learn the same–different task. As well, in Group 16, we found the same two patterns of performance—Categorical and Continuous—as in prior research (Castro et al., 2006 and Young and Wasserman, 2001). In Group 2, we again found the Categorical cluster, but we lost the genuine Continuous cluster and we observed a novel strategy: some participants developed a highly inclusive notion of “sameness” that applied to any array containing at least two identical icons. These findings indicate that individuals may deploy a multiplicity of possible strategies when learning a seemingly simple same–different discrimination.

► We trained participants on a nonverbal 2-item or 16-item same–different task.
► Half of the participants in the 2-item group failed to learn the discrimination.
► Learning to discriminate Same vs. Different arrays was easier with 16-item arrays.
► Nonlearners scored lower than learners on the Raven Matrices test.
► Individuals deploy multiple strategies when learning a simple same–different task.