The Nodal Distance Effect Measured by Different MTS Protocols, Sorting Tests, and Post-Class Tests

The nodal distance hypothesis states that responding in accordance emergent relations decreases as the number of nodes increases. A node is a stimulus that is used as functional stimuli in a relation of two or more conditional discriminations. Some studies have investigated different measures of responding in accordance with the nodal distance hypothesis, such as binary responding, reaction time, within-class preference test, and by transfer of function. Also, differences between amounts of training and testing trials may affect the responding in accordance with the nodal distance hypothesis. This study investigated the nodal distance hypothesis by controlling for differential training and testing trials if sorting tests could detect the nodal distance effect, and how the nodal distance effect occurs when measured by a post-class combined symmetry-transitivity test. Twenty participants were exposed for an MTS procedure with either (a) a simultaneous protocol or (b) a simple-to-complex protocol, a sorting test, a post-class combined symmetry-transitivity test, and another sorting test. The between-participant analysis shows that the nodal distance effect was more significant for participants who were exposed to the simultaneous protocol, no differential nodal structure sorting responses, and a decrease in the nodal distance effect when measured by a post-class test. The within-participant analysis shows that the nodal distance effect was more significant for participants who were exposed for the simple-to-complex protocol, no correlation between the nodal distance effect and nodal structure sorting responses during the first MTS test, and a post-class test predicted nodal structure sorting responses better than the first MTS test.