Imam, A. A. (2001).
Speed contingencies, number of stimulus presentations, and the nodality effect in equivalence class formation.
Journal of the Experimental Analysis of Behavior,
76, 265-288.
Two experiments compared performances on conditional
discrimination tasks using single-participant designs with and
without speed contingencies. Experiment 1 was a systematic
replication of Spencer and Chase (1996). Experiment 2 presented
equal numbers of training and testing trials. In each experiment,
2 female undergraduates participated. Each formed three
five-member and three seven-member equivalence classes in
Experiments 1 and 2, respectively. Response speed was an inverse
function of nodal number and relational type in Experiment 1, but
only of relational type (i.e., baseline, symmetry, transitivity,
and equivalence) in Experiment 2, with and without the speed
contingency. Accuracy tended to peak without the speed
contingency in both experiments. Adding the speed contingency
increased response speeds in both experiments, more so in
Experiment 2 with a lower limited hold for 1 participant. The
results of Experiment 2 cast doubt on previous reports of the
nodality effect and on the notion of "relatedness"
among class members, and they support a
reinforcement-contingency, rather than a structural, account of
equivalence class formation.
Key words: response speed, response accuracy, nodality, stimulus
equivalence, matching to sample, mouse click, college students