Lawrence T. Stoddard

Classroom applications of stimulus equivalence technology

We review basic concepts and methods of stimulus equivalence research and suggest applications in teaching rudimentary language arts skills in the classroom. We describe methods of establishing equivalence-based networks of matching-to-sample, writing, and naming performances. The methods may be used as a supplement to classroom instruction to assess whether standard curriculum-based approaches establish such integrated networks. Methods derived from equivalence research may be useful for remediation when traditional teaching approaches fail. Recent research suggests that direct focus on spelling performances may be required if entire networks of language arts skills are to be acquired. In addition, the equivalence relations themselves may require concentrated teaching in some children.

The Search for Stimulus Equivalence in Nonverbal Organisms

A currently unresolved issue in stimulus equivalence research is the relation of equivalence and language competence. The current consensus is that equivalence according to widely adopted criteria proposed by Sidman has not yet been demonstrated in nonverbal experimental subjects. This judgment rests primarily on the failure of nonhuman subjects to display the equivalence outcome under conditions comparable to those used with human subjects. We discuss theoretical and methodological issues that arise in research seeking to delineate the “lower limits” of equivalence phenomena in studies with laboratory animals or nonverbal humans. We propose a behavior-analytic approach to the question, examine the relationship between functional stimulus classes and equivalence classes, and describe some preliminary studies.

Stimulus classes in matching to sample and sequence production: The emergence of numeric relations

We investigated interrelationships among stimulus classes established in matching-to-sample and sequence-production tasks. The analysis focused on the matching and sequencing of quantities, numerals, and arbitrary forms in two individuals with mental retardation. The basic protocol involved: (a) establishing both matching and sequencing performances with some stimuli, (b) training sequencing with a new set of stimuli and assessing whether new matching performances emerged, and (c) training matching with a new set of stimuli and assessing whether new sequencing emerged. The results showed that sequence training did not readily lead to new matching performances, unlike prior research with college students. In contrast, training in matching to sample yielded emergent sequence production; these data support prior studies involving children and adults without developmental disabilities. The results extend prior stimulus class research and suggest an important role for stimulus control processes in the production of generative numeric performances.

Teaching coin equivalences via matching to sample.

A moderately mentally retarded woman learned coin equivalences (with 5-, 10-, and 15-cent values) via matching to sample. When taught to match two different coin stimuli to a printed price of equal value, she could then match the coin stimuli to each other and state their values without further training. Additional coin-matching and naming performances emerged after establishing the equivalence between a new coin stimulus and one member of an existing class of equivalent stimuli. The study extends research on stimulus class formation by examining its usefulness in a new application, in teaching a skill repertoire that requires mastery of large numbers of individual performances-monetary equivalences. Further, the study suggests efficient strategies for teaching functional money skills to developmentally limited populations.

Stimulus class formation and functional equivalence in moderately retarded individuals' conditional discrimination

Three mentally retarded humans first acquired a simple discrimination: Simultaneously displayed visual stimuli A1 and A2 functioned as S+ and S-, respectively. The subjects also acquired a conditional discrimination, learning to select visual stimuli B1 and B2 conditionally upon A1 and A2, respectively. Then, B1 and B2 were displayed without A1 or A2. Subjects selected B1, an emergent discrimination that showed that B1 and B2 had become functionally equivalent to A1 and A2, respectively. Two subjects next learned to select C1 and C2 conditionally upon B1 and B2, respectively. They also learned to select B1 and B2 conditionally upon D1 and D2, respectively. Subsequent simple discrimination probe trials displayed (a) C1 and C2 and (b) D1 and D2. On the former, the subjects nearly always selected C1. On the latter, they initially selected D1 and D2 about equally often. Thus, the emergence of simple discrimination appears to depend on a specific experimental history.

Positive and Negative Stimulus Relations in Severely Retarded Individuals' Conditional Discrimination.

Abstract Four low-functioning mentally retarded subjects learned conditional discrimination performances in two-comparison auditory-visual and visual-visual identity matching-to-sample paradigms. Auditory stimuli were spoken food names and visual stimuli were food items. The subjects were also taught, by means of a stimulus shaping program, to perform a variant of the auditory-visual task in which only one comparison was displayed on each trial: if the correct one was displayed, to select it; if an incorrect one, to select a blank alternative. Following the program, subjects performed auditory-visual conditional discriminations on the basis of relations between either the sample and the correct comparison (positive relations) or the sample and the incorrect comparison (negative relations). Additional tests, conducted in the single comparison positive and negative relations (1) in auditory-visual performances with foods that had a two-comparison history, but had not been used in stimulus shaping, and (2) in visual-visual identity performances. All subjects proved capable of such performances. The results suggested that acquisition of both postive and negative conditional relations may occur when developmentally-limited individuals are trained with matching-to-sample procedures. This outcome may be relevant to designing remedial communication programs for this population—especially those concerning generalized “Yes”-“No” concepts.

Studies of exclusion in individuals with severe mental retardation

Exclusion performances in matching to sample are demonstrated when subjects select experimentally undefined comparison stimuli in the presence of undefined sample stimuli, apparently by rejecting defined comparison stimuli. Several studies have documented exclusion performances in a small number of individuals with severe mental retardation. These studies also demonstrated the potential of exclusion procedures for establishing prerequisites for emergent naming performances. The present study examined exclusion in a larger cohort of subjects. Initial experiments asked two questions. First, how reliably would exclusion performances be demonstrated? Second, would those performances be followed by emergent naming, and, if so, how reliably? Follow-up experiments examined the stimulus control basis for exclusion performances. Our findings and conclusions can be summarized as follows: First, reliable exclusion was demonstrated in nearly all subjects. Second, naming performances typically emerged. These performances were seen in the context of a recent experimental history of matching to sample and of naming baseline stimuli in the experimental format. Third, apparent exclusion may sometimes result from relating undefined sample and comparison stimuli. Together, our findings suggest potentially effective strategies for teaching people with mental retardation and point to variables that should be considered when designing exclusion-based teaching interventions.

Teaching money skills through stimulus class formation, exclusion, and component matching methods: Three case studies

This paper describes novel methodology for teaching monetary skills to mentally retarded individuals. The goal of the methodology is to generate such skills with relatively little explicit training. To do so, the procedures were designed to produce emergent new behavior through stimulus class formation, exclusion, and matching of stimulus components. Three case studies demonstrate the methods and provide illustrative supporting data.

Complex stimulus relations and exclusion in severe mental retardation

Abstract Exclusion of stimuli involved in complex stimulus relations was examined in a severely retarded young man. On two-comparison arbitrary auditory-visual matching-to-sample trials, the subject learned first to select (a) either of two different food items in response to the same spoken-name sample of (b) the same food item in response to either of two different spoken names. Then, on exclusion test trials, a food involved in one or the other type of relation was displayed with a novel food (i.e., one not yet related to a name); the spoken-name sample was also novel. On such trials, the subject selected the novel food, apparently excluding the food involved in learned relations. The study systematically replicates and extends research on exclusion performance of low-functioning mentally retarded individuals and provides additional data on relational learning in this population.

A stimulus shaping method for teaching complex motor performance to severely and profoundly retarded individuals

Abstract A program demonstrated the sufficiency of stimulus shaping methods for teaching a complex motor task. The methods differ from typical applications of stimulus shaping in discrimination learning, where the subjects response remains invariant. Instead, the program reported here was designed to generate progressive changes in the topography of the subjects response as a function of gradual changes in the stimuli. Severely and profoundly retarded children and young adults were taught to exchange tokens in an automatic device to produce food deliveries. All stimulus changes were carried out through gradual shifts in mechanically arranged contingencies. The token initially projected from a slot, was then lowered gradually, supported by a line; after reaching a tray, the line was removed in several steps until tokens were delivered by an automatic dispenser. The methods may suggest alternative techniques to investigate when problems are encountered or anticipated with programs that rely on prompting or guidance by a teacher.