Associative changes in excitors and inhibitors differ when they are conditioned in compound

When an AB stimulus compound is reinforced or nonreinforced, there are asso ciative changes in both A and B elements. In many contemporary theories tho se changes are viewed as governed by a common error term. computed as the d iscrepancy between the total associative strength of the AB compound and th at supported by the trial consequence. This implies that if A and B are equ ally salient, then the magnitude of their associative change should be the same, whatever their strengths prior to the AB trial. This implication was explored for a compound consisting of an excitatory A and an inhibitory B. A novel assessment procedure avoided the difficulty of making comparisons a t different locations on the performance scale. Three experiments using a m agazine approach preparation in rats and 3 using autoshaping in pigeons fou nd evidence contradicting this implication. The excitatory A changed less t han the inhibitory B when the compound was reinforced but more than B when the compound was nonreinforced.