Second-Order Conditioning and Conditioned Inhibition in Different Moments of the Same Training: The Effect of A+ and AX- Trial Number

Abstract

The feature negative discrimination (A+/AX-) can result in X gaining excitatory properties (second-order conditioning, SOC) or in X gaining inhibitory properties (conditioned inhibition, CI), a challenging finding for most current associative learning theories. Research on the variables that modulate which of these phenomena would occur is scarce but has clearly identified the trial number as an important variable. In the set of experiments presented here, the effect of trial number was assessed in a magazine training task with rats as a function of both the conditioning sessions and the number of A+ and AX- trials per session, holding constant the total number of trials per session. The results indicated that SOC is most likely to be found at the beginning of training when there are many A+ and few AX- trials, and CI (as assessed by a retardation test) is most likely to be found at the end of training when there are few A+ and many AX- trials. Both phenomena were also found at different moments of training when the number of A+ trials was equal to the number of AX- trials. These results cannot be predicted by acquisition-focused associative models but can be predicted by theories that distinguish between learning and performance.

Keywords: associative learning models; conditioned inhibition; cue interaction; feature negative discrimination; second-order conditioning.

FIGURE 1

Conditioning phase in Experiment 1. PreX-X differences (±SEM), averaged for the two X− presentations per session in conditioning, are displayed. The black line represents the group that was trained with 14 A+, two AX−, 12 F−, and two X− presentations per session in conditioning. The gray line represents the group that was trained with 14 A+, two BX, 12 F−, and two X− presentations per session.

FIGURE 2

Retardation test in Experiment 1. PreX-X differences (±SEM), averaged for the 10 X+ presentations per session in the retardation test, are displayed. The black line represents the group that was trained with 14 A+, two AX−, 12 F−, and two X− presentations per session in conditioning. The gray line represents the group that was trained with 14 A+, two BX, 12 F−, and two X− presentations per session. In the retardation test, both groups received 10 X+ presentations per session.

FIGURE 3

Conditioning phase in Experiment 2. PreX-X differences (±SEM), averaged for the two X− presentations per session in conditioning, are displayed. The black line represents the group that was trained with eight A+, eight AX−, six F−, six F+, and two X− presentations per session in conditioning. The gray line represents the group that was trained with eight A+, eight BX−, six F−, six F+, and two X− presentations per session.

FIGURE 4

Retardation test in Experiment 2. PreX-X differences (±SEM), averaged for the 10 X+ presentations per session in retardation, are displayed. The black line represents the group that was trained with eight A+, eight AX−, six F−, six F+, and two X− presentations per session in conditioning. The gray line represents the group that was trained with eight A+, eight BX−, six F−, six F+, and two X− presentations per session. In the retardation test, both groups received 10 X+ presentations per session.

FIGURE 5

Conditioning phase in Experiment 3. PreX-X differences (±SEM), averaged for the two X− presentations per session in conditioning, are displayed. The black line represents the group that was trained with five A+, 11 AX−, three F−, nine F+, and two X− presentations per session in conditioning. The gray line represents the group that was trained with five A+, 11 BX−, three F−, nine F+, and two X− presentations per session.

FIGURE 6

Retardation test in Experiment 3. PreX-X differences (±SEM), averaged for the 10 X+ presentations per session in retardation, are displayed. The black line represents the group that was trained with five A+, 11 AX−, three F−, nine F+, and two X− presentations per session in conditioning. The gray line represents the group that was trained with eight A+, five A+, 11 BX−, three F−, nine F+, and two X− presentations per session. In the retardation test, both groups received 10 X+ presentations per session.

FIGURE 7

Simulations of associative properties acquired by X according to Wagner’s Sometimes Opponent Processes (SOP) model, performed using the SOP model simulator (Byers et al., 2017), for the 20 sessions of the experimental designs reported. The left panel displays the simulation for Experiment 1, in which the experimental group (black line) was trained with 14 A+, two AX−, 12 F−, and two X− trials per session, and the control group (gray line) was trained with 14 A+, two BX−, 12 F−, and two X− trials per session. The central panel displays the simulations for Experiment 2, in which the experimental group (black line) was trained with eight A+, eight AX−, six F−, six F+, and two X− trials per session, and the control group (gray line) was trained with eight A+, eight BX−, six F−, six F+, and two X− trials per session. The right panel displays the simulations for Experiment 3, in which the experimental group (black line) was trained with five A+, 11 AX−, three F−, nine F+, and two X− trials per session, and the control group (gray line) was trained with five A+, 11 BX−, three F−, nine F+, and two X− trials per session.