The effects of outcome value and pretraining on the differential outcomes effect in a visual discrimination task with rats

Abstract

The differential outcomes effect (DOE) occurs when learning is facilitated by the delivery of different outcomes (e.g., food vs. water) correlated with different responses. The current experiments examined the effects of reinforcer value and pretraining with different outcomes compared to mixed-outcomes (MO) groups, in which the two outcomes are uncorrelated. Rats were trained to press the left lever during one stimulus (a steady light) and right lever during another (a flashing light). Experiment 1 compared DO and MO groups when using higher-valued versus lower-valued reinforcers. The higher value DO group acquired the discrimination faster relative to its respective MO group. Experiment 2 examined pretraining with DO or MO prior to DO or MO discrimination training. There was no direct effect of pretraining, but only the group with MO pretraining demonstrated a typical DOE. Though more research is needed, higher-value rewards may facilitate learning, but only after overcoming a response bias.