Academic journal article The Psychological Record

The Effects of Different Training Structures in the Establishment of Conditional Discriminations and Subsequent Performance on Tests for Stimulus Equivalence

Academic journal article The Psychological Record

The Effects of Different Training Structures in the Establishment of Conditional Discriminations and Subsequent Performance on Tests for Stimulus Equivalence

Article excerpt

Stimulus equivalence is defined as the interchangeability of stimuli within a class (Green & Saunders, 1998). The defining characteristic of stimulus equivalence is responding in accord with reflexivity, symmetry, and transitivity (e.g., Sidman & Tailby, 1982). Stable baseline responding, a prerequisite for testing for emergent relations, is established through various training protocols and training structures. The training structures and protocols seem to have dissimilar effects on responding in the subsequent stimulus equivalence tests. A training protocol defines the sequence of training and type of tests. Imam (2006) has given an account of three different training protocols: simple-to-complex, simultaneous, and complex-to-simple.

The term training structure has been used to refer to the sequence of conditional discriminations and the arrangements that link stimuli in baseline training (R. R. Saunders & Green, 1999). The training structures have been labeled Linear Series (LS), Many-to-One (MTO) or Comparison-as-Node (CaN), and One-to-Many (OTM) or Sample-as-Node (SaN) (see K. J. Saunders, Saunders, Williams, & Spradlin, 1993, for an overview). A node can be defined as a stimulus that is connected to at least two other stimuli. However, the effects of the number of nodes can only be studied when using a linear series training structure, because increasing the number of members in each class does not influence the number of nodes in MTO or OTM. A number of studies have found nodal effects, i.e., stimulus equivalence outcome decrease and reaction time increase, to be a function of the number of nodes (e.g., Arntzen & Holth, 2000b; Bentall, Jones, & Dickins, 1999; Fields, Landon-Jimenez, Buffington, & Adams, 1995; Kennedy, 1991). On the other hand, some other findings contradict this when the number of trials is equal per nodal number (Imam, 2006).

Dymond and Rehfeldt (2001) have seen reaction time as an important supplementary measure in research on derived relations. A number of studies have shown a characteristic pattern of reaction time to comparison stimuli, that is, an increase from the last training trials to the first test trials and a decrease during testing (e.g., Arntzen, 2004), and a substantially greater increase for equivalence trials compared to symmetry trials (e.g., Wulfert & Hayes, 1988).

There are two main reasons for the interest in investigating responding in accordance with stimulus equivalence as a function of different training structures. First, in the original analyses of stimulus equivalence, the three training structures were expected to lead to the same outcome on test for stimulus equivalence. Second, a number of experiments have shown that responding in accord with stimulus equivalence varies as a function of different training structures (e.g., Arntzen, 2007). Some studies have found that MTO is the most effective training structure (Barnes, as cited in Barnes, 1994; Hove, 2003; K. J. Saunders et al., 1993; R. R. Saunders, Chaney, & Marquis, 2005; R. R. Saunders, Drake, & Spradlin, 1999; R. R. Saunders & McEntee, 2004), while others have found results in favor of OTM (Arntzen, 2004; Arntzen & Holth, 1997, 2000a). Although there is at present no clear evidence of the differential effectiveness of MTO and OTM structures, the LS training structure has consistently been shown to be the least effective in producing stimulus equivalence with a simultaneous protocol.

However, most of the studies that have shown the superiority of the MTO training structure have used a two-choice procedure (see, e.g., Barnes, 1992; K. J. Saunders et al., 1993; R. R. Saunders et al., 1999; R. R. Saunders, Wachter, & Spradlin, 1988; Spradlin & Saunders, 1986). It is therefore a possibility that the S-control could explain the differences in stimulus equivalence outcome between the studies. Negative contextual control can be reduced by using three or four choices in the matching-to-sample training (Carrigan & Sidman, 1992; Johnson & Sidman, 1993; Sidman, 1994). …

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