Abstract
We asked younger and older human participants to perform computer-based configural discriminations that were designed to detect acquired equivalence. Both groups solved the discriminations but only the younger participants demonstrated acquired equivalence. The discriminations involved learning the preferences [“like” (+) or “dislike” (−)] for sports [e.g., tennis (t) and hockey (h)] of four fictitious people [e.g., Alice (A), Beth (B), Charlotte (C), and Dorothy (D)]. In one experiment, the discrimination had the form: At+, Bt−, Ct+, Dt−, Ah−, Bh+, Ch−, Dh+. Notice that, e.g., Alice and Charlotte are “equivalent” in liking tennis but disliking hockey. Acquired equivalence was assessed in ancillary components of the discrimination (e.g., by looking at the subsequent rate of “whole” versus “partial” reversal learning). Acquired equivalence is anticipated by a network whose hidden units are shared when inputs (e.g., A and C) signal the same outcome (e.g., +) when accompanied by the same input (t). One interpretation of these results is that there are age-related differences in the mechanisms of configural acquired equivalence.
Highlights
Experiments on “acquired equivalance” have revealed important information about the way in which animals encode stimulus representations
It is notable that non-configural forms of acquired equivalence are possible (e.g., Honey and Hall, 1989) but they are interpretable in simpler terms than those considered here (e.g., Ward-Robinson and Hall, 1999)
Inspection of the two Y groups, indicates that group YW recovered from the disruption of the reversal more quickly than group YP. No such pattern can be seen in the O groups: groups OW and OP show no obvious difference in recovery. This description of the data was supported by an analysis of variance (ANOVA) with within-subject variables of: (1) cycle, (2) established training versus reversal stage, and (3) trial; and between-subject variables of: (1) age (i.e., Y versus O), and (2) reversal group (i.e., W versus P)
Summary
Experiments on “acquired equivalance” have revealed important information about the way in which animals encode stimulus representations. For group Whole, all trial types were reversed (i.e., At−, Ac+, Bt+, Bc−, Ct−, Cc+, Dt+, Dc−) but for group Part only half of the trial types were reversed (At+, Ac−, Bt−, Bc+, Ct+, Cc−, Dt+, Dc−) Both groups’ performances were reduced by the reversal from the original stages and both recovered; group Whole’s performance recovered more quickly than group Part’s did. Notice that in the pre-reversed discrimination these Skinner boxes indicate the equivalent reinforcement arrangements for the tone and click. Expressed, it is as though rats’ representations of Skinner boxes A and C (and B and D) had “acquired equivalence” during pre-reversal training. It is notable that non-configural forms of acquired equivalence are possible (e.g., Honey and Hall, 1989) but they are interpretable in simpler terms than those considered here (e.g., Ward-Robinson and Hall, 1999)
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