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Investigating relatedness and nodality in stimulus equivalence

Stimulus equivalence describes how a group of stimuli can be trained to be ‘equal’, part of one group (equivalence class) where all stimuli are substitutable by each other. Relatedness deals with how stimuli in an equivalence class may not be equal, but rather have differing magnitudes of relations depending on how many stimuli are between two related stimuli. The stimuli in that are between two related stimuli in an equivalence class are called nodes. The issue of nodality in relatedness has been of interest to behavioural researchers. In this study, an experiment was conducted to test the strength of the relations between stimuli in trained equivalence class, which was a replication of several previous studies, with methodological improvements. The strength of stimulus-stimulus relations was tested by first using the simultaneous training method to establish two 6-member, 4-node equivalence classes, after which within-class preference testing was used. Of the 12 participants who took part in the experiment, seven participants were not able to successfully form the two 6-member equivalence classes, with the remaining five participants successfully able to form the two 6- member equivalence classes – demonstrated through achieving criterion (90%) response accuracy during the simultaneous protocol testing phase. The participants who completed the preference testing demonstrated response control by nodality, as they regularly preferred comparison stimuli that were nodally proximal to the sample; and in the case of one participant, responding was entirely consistent with the effects of nodality. That is, they always preferred the comparison stimuli that were nodally proximal to the sample stimuli. Furthermore, on the occasions when the participants did select the nodally distal comparison stimuli, they took longer to make the selection than when they selected the nodally proximal stimuli. On preference testing probes that did not differ in nodal distance (comparison stimuli were an equal nodal distance from the sample stimuli), participants showed no preference for either of the comparison stimuli by selecting both the comparison stimuli approximately an equal number of times. These findings are consistent with earlier studies which involved using various training methods to establish equivalence classes, then testing for nodality effects on stimulus-stimulus relations within the established equivalence classes. Therefore, with the methodological improvements applied in the study, nodality was demonstrated, suggesting that stimuli in an equivalence class are related differentially.
Type of thesis
Chand, G. C. (2020). Investigating relatedness and nodality in stimulus equivalence (Thesis, Master of Applied Psychology (MAppPsy)). The University of Waikato, Hamilton, New Zealand. Retrieved from https://hdl.handle.net/10289/13758
The University of Waikato
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