Learning & Behavior - June 2018

Volume 46, Issue 2

**Comparing cognition by integrating concept learning, proactive interference, and list memory; Wright, A. A., Kelly, D. M., & Katz, J. S.**
Theoretical paper describing approaches for training various species on same/different abstract-concept tasks

**Divergences in learning and memory among wild zebrafish: Do sex and body size play a role?; Roy, T., & Bhat, A.**
The authors aimed to explain individual differences in wild zebrafish learning and memory. To do this they studied fish from four populations across India, testing individual fish on a food reward task requiring them to navigate a maze to find the food reward chamber. Information about the fish habitats (relative abundance of zebrafish, relative abundance of predatory fish, the diversity of the substrate and vegetation of the native habitats) and their sex and body size were looked at to explain variations in maze performance and errors during training. The ability of the fish to remember the learned task was also tested after 4-days. The results showed that zebrafish learned the maze task across training trials, with three populations learning quicker than the fourth population. Individual differences were seen in learning across the populations, with one population varying significantly more than the others. The authors emphasize that environmental factors explain diversity in learning.

**Measuring the “transfer of meaning” through members of equivalence classes merged via a class-specific reinforcement procedure; Silveira, M. V., Mackay, H. A., & de Rose, J. C.**
The authors aimed to test the prediction that class-specific reinforcers go beyond operant conditioning and stimulus control by becoming members of the category and the reinforced information being transferred to all members of the category, despite the reinforcement having only be trained to one member. The task used to test this theory involved categorization of faces portraying emotions and abstract stimuli equivalent to them. Categorization of these stimuli to the same category would demonstrate transfer learning. The categories (emotion faces and arbitrary forms) were taught using MTS training and class-specific reinforcers (one-to-many training design). Relational learning of “meaning” between category members related only by a common reinforcer was then tested. The researchers found that arbitrary stimuli made equivalent to emotion faces (via associative training with a common reinforcer) were categorized as the same category, reflecting transfer of meaning.

**Associative structure of second-order conditioning in humans; Craddock, P., Wasserman, J. S., Polack, C. W., Kosinski, T., Renaux, C., & Miller, R. R.**
Operational second-order conditioning (SOC) was defined as S1-US pairings followed by S2-S1 pairings. S1 is a first-order conditioned stimulus, S2 is a second-order conditioned stimulus, and US remains an unconditioned stimulus. The researchers aimed to find the associative structure underlying SOC, specifically post-SOC extinction of S1 resulting in extinction of S2 in SOC without direct S2-outcome associations. The results suggested that S2 responding was dependent on the associative status of S1.