Association for Behavior Analysis International

Recent studies have employed neuroscientific techniques to measure for derived stimulus-stimulus relations produced by MTS procecures. This symposium is comprised of four talks describing some of the uses of such techniques for assessments of covert behavior evoked when participants are given to equivalence protocols. The fisrt presentation will report an investigation that aimed at verifying how different numbers of meaningful and abstract stimuli affects number of training trials, equivalence class responding and eye-movements. The other presentations will focus on the Event-Potential Techinique (ERP) for detection of measurable changes in the brain’s activity resulting from derived stimulus-stimulus relations established by different MTS protocols. Thus, the second study will describe how ERPs can be sensitive to word-like sample stimulus. The third presentation will demonstrate how stimulus familiarity and training stucture impact on the ERPs waveforms. Finally, the last presentation will show how the ERPs related to stimulus equivalence can be “delayed” by extensive experience with MTS trials testing for transitivity and equivalence relations. Overall, the data discussed here have direct implication for the experimental analysis of complex behavior.

The N400 is an event-related brain potential sensitive to the semantic relations in naturally occurring language. To illustrate, when words are semantically related (e.g., butter-bread) the N400 will be more negative than N400 evoked by unrelated words (e.g., grease-bread). The the peak amplitudes can be used to differentiate the types of experimentally-defined stimulus relations established by Matching-to-Sample (MTS) procedures. That is, the N400 will be more negative for the “non-equivalent” than to the “equivalent” stimulus-stimulus relations. Research reported here concerns the impact of MTS training parameters, specifically, the explicit training of name-object relations, in the N400 waveforms.In this regard, a between groups design was used, in which both groups were exposed to the same experimental procedures, except for the stimuli used, so that Group 1 used only abstract figures, and Group 2 used both pseudowords and abstract figures, during MTS training. Waverforms obtained from participants shows a clear N400 effect for Group 2, but not for Group 1. These results are discussed considering the possibility that this effect reflects a difference between groups in the degree of relatedness between stimuli in equivalence classes.

N400 is an event-related potential (ERP) measured approximately 400 ms after presentation of two incongruent stimuli compared with congruent stimuli. This also applies when the related stimuli are not directly trained. In the current experiment, six conditional discriminations were trained in a matching-to-sample procedure with the goal to form three 3-member classes with C stimuli as meaningful stimuli in a many-to-one training structure. The participants (one group with adults with high function autism and one group without such diagnosis) then were tested in a priming-procedure, with related and unrelated stimuli pair. N400 was measured in this phase. The results show a N400 response produced in both groups, similar to each other, but with a small difference between related and unrelated stimuli pairs in the ASD group.

Haimson et al., (2009) reported that N400 waves for non-related and related pairs showed a clear and robust differentiation between participants who had been exposed to MTS test trials. On the other hand, a delayed emergence of the N400 was observed among participants given only to series of MTS baseline training trials. In our study we manipulated the nature of the sample stimuli using photographs of human faces expressing emotions. Adults were allocated to two groups. One group was submitted to AB, AC, AD and AE baseline conditional discrimination training procedures and then exposed to test trials that tested for the emergence of transitive relations (BC, BD and BE) and equivalence relations (CB, DB and EB). The other group was given only to MTS baseline training. Finally, both groups were exposed to semantic judgment trials while the brain activity of each participant was recorded continually. Contrary to Haimson et al., (2009)’s observation, our data showed delayed N400 among the participants given to transitivity and equivalence tests. Apparently, the ERPs were not affected by the emotional valances of the faces used as samples.