Maintained nodal-distance effects in equivalence classes.
Nodal distance weakens emergent relations even after equal training, so sequence your baseline relations from short to long.
01Research in Context
What this study did
Einfeld et al. (1995) built equivalence classes with adults who had no disabilities.
They trained A-B and B-C relations, then tested for A-C (one node) and A-D (two nodes).
Everyone got the same amount of training; the team wanted to see if distance still mattered.
What they found
All twelve people showed weaker responding as nodal distance grew.
Only two adults passed every equivalence test, yet the distance effect stayed.
Even after equal practice, two-node relations were harder than one-node relations.
How this fits with other research
Chand et al. (2022) repeated the test with tighter controls and got the same nodality pattern.
Their replication shows the distance effect is real, not a fluke of priming or history.
Brown et al. (1994) saw the same stair-step pattern in students with ID learning sight words.
Christian et al. (1997) later flipped the idea: pretraining classes with extra nodes sped up new learning.
Why it matters
When you build stimulus classes, put the most useful relation closest to the learner’s starting point.
Train short chains first, then add nodes instead of jumping straight to long chains.
This small shift cuts errors and saves time in both clinic and classroom programs.
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Join Free →Map your current class and teach the one-node relation first; add the two-node relation only after the first is solid.
02At a glance
03Original abstract
Twelve subjects were trained to select one of two stimuli from a pair (the B pair) when presented with one of two stimuli from another pair (the A pair), thus establishing two AB relations, A1-B1 and A2-B2. In a similar fashion, additional stimuli were used to establish BC, CD, and DE relations. Trials used to train all relations occurred in each session. Once performances were established, probe trials were introduced that tested for the emergence of untrained relations (e.g., B1-D1 or A1-E1). These emergent relations were categorized according to nodal distance (i.e., the number of stimuli across which transitivity would have to hold in order for the relation to emerge). For example, a test for A2-C2 crosses one node (B2), whereas a test for A1-E1 crosses three nodes (B1, C1, and D1). Only 2 of the subjects formed equivalence classes. The evocation of class-appropriate responding by each emergent-relation probe was an inverse function of nodal distance for all 12 subjects. In addition, performance on the originally trained relations was disrupted by the introduction of probes. The 2 subjects who exhibited equivalence classes were then trained to make different numbers of key presses in the presence of each of the four A and E stimuli. In a response-transfer test, the B, C, and D stimuli evoked the responses trained to the A and E stimuli in the same equivalence class. Likelihood of class-appropriate responses was an inverse function of nodal distance, and this pattern persisted across testing. Reaction times in the transfer test were an inverted U-shaped function of nodal distance. Because training of the baseline relations occurred concurrently and the B, C, and D stimuli were presented an equal number of times before the transfer test, the test performances illustrate effects of nodal distance that were not confounded by order or amount of experience with the stimuli. The results imply that ordered, sequential exposure to individual stimulus relations may facilitate the development of equivalence classes and that the relatedness of stimuli within an equivalence class is a relatively permanent inverse function of nodal distance.
Journal of the experimental analysis of behavior, 1995 · doi:10.1901/jeab.1995.64-129