Overshadowing, but not relative validity, between the elements of an outcome during human associative learning

Overshadowing and relative validity constitute two phenomena that inspired the development of the Rescorla-Wagner model in 1972. They demonstrate that cues will interact with one another for an association with the presence or absence of an outcome. Here, three experiments sought to explore whether these two effects extended to outcomes using a food allergist paradigm with human participants. In Experiment 1 (overshadowing) participants received trials in which a cue was followed by a compound of two outcomes (A-O1O2). Test trials revealed that participants learned less about the A-O2 association than they did between a control cue C, which had been paired with O2 in isolation (C-O2) in training - thus demonstrating an outcome overshadowing effect. In Experiment 2 (relative validity) participants received true discrimination trials, in which A was paired with an O1O3 compound and B was paired with an O2O3 compound, and pseudo discrimination trials, in which C and D were paired on 50% of the trials with an O4O6 compound and on the remaining trials with an O5O6 compound. Consequently, O3 is less well predicted by A and B relative to O1 and O2, whereas O6 is equally well predicted by C and D relative to O4 and O5. Despite the relative validity of A and B for O3 being less than the relative validity of C and D for O6, the ratings of A and B for O3 were the same as C and D for O6. This failure to observe an outcome relative validity effect was reproduced in Experiment 3, which replicated Experiment 2, but with an adjustment made to the number of training trials given to participants. These results are discussed in terms of a real-time development of the Rescorla-Wagner model provided by Wagner (1981).