Teaching Stimulus-Stimulus Relations to Minimally Verbal Individuals: Reflections on Technology and Future Directions.

This paper discusses recent methodological approaches and investigations that are aimed at developing reliable behavioral technology for teaching stimulus-stimulus relations to individuals who are minimally verbal and show protracted difficulty in acquiring such relations. The paper has both empirical and theoretical content. The empirical component presents recent data concerning the possibility of generating rapid relational learning in individuals who do not initially show it. The theoretical component (1) considers decades of methodological investigations with this population and (2) suggests a testable hypothesis concerning some individuals exhibit unusual difficulties in learning. Given this background, we suggest a way forward to better understand and perhaps resolve these learning challenges.

Written lists as mediating stimuli in the matching-to-sample performances of individuals with mental retardation.

Students with mental retardation learned to write lists in order to perform a matching task that they could not do otherwise. After an initial assessment phase, reinforcement was arranged in the computerized tasks to follow selection of the six pictures that were identical to those in the six-picture samples presented. In Study 1, even though the participants wrote a list of the names of the six sample pictures on each trial, read a list, or did both, they often made errors when a brief delay preceded picture selection. In contrast, performance was nearly perfect when a list was written, read, and remained available at the time of picture selection, suggesting that the list served to mediate the delays. Study 2 examined the stimulus control by two- and six-picture samples over the list writing. Early during testing, 1 participant refrained from writing lists on two-picture trials but wrote lists on six-picture trials, thereby maximizing reinforcement and minimizing its delay; the other participant showed this pattern of list writing after supplemental training. The studies suggest methods for establishing a rudimentary repertoire of mediating behavior that has relevance for teaching instruction-following skills in natural settings.

Picture naming, matching to sample, and head injury: a stimulus control analysis.

Computer-based procedures were used to examine oral naming and matching-to-sample performances in an adult with a head injury. Relatively few errors occurred when pictures were (a) named, (b) matched to dictated names presented simultaneously, (c) matched to dictation after a delay, and (d) matched to identical pictures presented simultaneously. More errors occurred on delayed than on simultaneous identity matching. On delayed matching trials, fewer errors occurred when instructions to name the samples were given.

Transitivity and emergent sequence performances in young children.

Children taught to sequence pairs of visual stimuli also performed additional sequences without direct training. In Experiment 1, the children were trained to produce a six-stimulus sequence (A > B > C > D > E > F) with one set of forms, and five overlapping two-stimulus sequences (A > B, B > C, C > D, D > E, and E > F) with another set of forms. Few of the children succeeded on tests for the untrained two- (e.g., B > D and B > E) and six-stimulus sequences derivable from the two-stimulus training. The children in Experiments 2 and 3 received only the overlapping sequence training before testing with refined protocols: Nearly all succeeded on tests of emergent sequences involving two, three, four, five, and six stimuli. The results suggest methods for examining transitive relations between pairs of the stimuli used in training and the development of a relation of order among all six of the stimuli involved.

Naming, the formation of stimulus classes, and applied behavior analysis.

The methods used in Sidman's original studies on equivalence classes provide a framework for analyzing functional verbal behavior. Sidman and others have shown how teaching receptive, name-referent matching may produce rudimentary oral reading and word comprehension skills. Eikeseth and Smith (1992) have extended these findings by showing that children with autism may acquire equivalence classes after learning to supply a common oral name to each stimulus in a potential class. A stimulus class analysis suggests ways to examine (a) the problem of programming generalization from teaching situations to other environments, (b) the expansion of the repertoires that occur in those settings, and (c) the use of naming to facilitate these forms of generalization. Such research will help to clarify and extend Horne and Lowe's recent (1996) account of the role of verbal behavior in the formation of stimulus classes.

Teaching computer-based spelling to individuals with developmental and hearing disabilities: transfer of stimulus control to writing tasks.

Computer-based instruction may yield widely useful handwritten spelling. Illustrative cases involved individuals with mental retardation and hearing impairments. The participant in Study 1 matched computer pictures and printed words to one another but did not spell the words to pictures. Spelling was then taught using a computerized procedure. In general, increases in the accuracy of computer spelling were accompanied by improvements in written spelling to pictures. Study 2 extended these results with a 2nd participant. After initial training, spelling improved in the context of a retrieval task in which the participant (a) wrote a list of the names of objects displayed on a table, (b) selected the objects from a shelf, and (c) returned the objects to the table. Nearly perfect accuracy scores declined on some retrieval trials conducted without a list, suggesting that the list may have served a mediating function during retrieval. Transfer of stimulus control of computer-based teaching to the retrieval task may have been attributable to the existence of stimulus classes involving pictures, objects, and printed words.

Delayed matching to complex samples and the formation of stimulus classes in children.

In two experiments (ns = 3 plus a previously tested child, and 2, respectively), children learned delayed matching with complex samples, each consisting of a form and a printed nonsense word. Forms or printed words were comparison stimuli. For form comparisons, selecting the form identical to that in the preceding sample was reinforced. For printed word comparisons, selecting the word identical to that in the preceding sample was reinforced. During testing, the children then matched the forms and printed words to one another. In subsequent training, the samples were (a) old forms combined with new words or (b) old words combined with new forms. Novel matching performances among forms and words appeared across these training phases. Word-form contiguity in a matching-to-sample context may contribute to the formation of classes of stimuli that may be equivalent.

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.

Matching to complex samples and stimulus class formation in adults with autism and young children.

Adults with autism and young children first learned to match one-element comparison stimuli to two-element sample stimuli. Test conditions then examined whether each of the individual sample elements (a) controlled selections of the comparison stimuli to which they were related during training, (b) were interchangeable with one another as either sample or comparison stimuli, and (c) were interchangeable with the original comparison stimuli. Test data were positive and suggested the formation of three-member stimulus classes. Subsequent experiments demonstrated the formation of four-member classes by (a) adding novel stimuli by training outside the original context; (b) adding novel stimulus elements to the two-element samples used during baseline training; and (c) training with three-element rather than two-element sample stimuli from the outset. Results suggest that acquisition of stimulus classes may be one of the benefits of broad rather than restricted attention to the components of complex stimuli.

Sequence learning in individuals with behavioural limitations.

The production of sequences by two mentally retarded adults and a normally capable preschooler was assessed after each was trained to touch five physically dissimilar and nonrepresentative forms in an experimenter-specified order (denoted A1-->A2-->A3-->A4-->A5). Performance on the 10 constituent two-term sequences was examined (e.g. A-->A2, A2-->A3, A1-->A3 and A2-->A4). The probe data were largely consistent with the five-term sequence performance trained explicitly and suggest the formation of stimulus relations based on relative position rather than a rote stimulus-response chain. The procedures and results were replicated with a second five-term sequence (B1-->B2-->B3-->B4-->B5). The subjects' performances were also assessed on trials in which mixtures of the two sets of stimuli were presented as either two-term probes (e.g. A2-->B4 and B2-->A4; with all three subjects) or five-term probes (e.g. A1-->B2-->A3-->B4-->A5; with the two adult subjects). Again, the subjects' performances were consistent with their baseline training. The mixed-probe data extend prior research on sequence production and suggest the formation of classes of mutually substitutable sequence stimuli. The overall findings highlight the importance of experiential variables in the formation of ordinal relations in developmentally limited individuals.

Delayed identity matching to complex samples: teaching students with mental retardation spelling and the prerequisites for equivalence classes.

Students with mental retardation learned delayed matching to sample in which some of the trials involved complex sample stimuli, each consisting of a picture and a printed word. A touch to the sample complex removed it from the computer display and produced either picture comparisons or a choice pool of letters. If the comparisons were pictures, selecting the picture identical to the preceding sample was reinforced. If the letters appeared, letter-by-letter construction of the preceding printed word sample was reinforced. The procedure engendered new constructed-response spelling performances to pictures and dictated words as samples. The emergence of relations among different sets of printed words (paired with the same pictures) suggested the formation of equivalence classes. One subject's data suggest that written spelling, oral spelling, and naming also may emerge as byproducts of the intervention.

Assessing control by elements of complex stimuli in delayed matching to sample.

A series of six experiments examined delayed identity matching-to-sample performances of subjects with mental retardation. The stimuli were either one or two simultaneously displayed forms. When the reinforcement contingencies required that only one form exert discriminative control, all subjects achieved high accuracy scores. However, accuracy scores were substantially lower when the contingencies required discriminative control by two forms, suggesting restricted stimulus control. The decline in matching accuracy appeared to reflect selective losses of conditional control by sample stimuli and shifts in control to features of the comparison stimulus displays. The experiments suggest improved techniques for assessing control by complex stimuli and for evaluating the effects of procedures that seek to broaden restricted stimulus control. The results challenge interpretations based on stimulus-generalization decrement or shared attention.

Conditional stimulus control of childrens' sequence production.

Normally capable children were first taught to touch in sequence each of a set of five physically dissimilar stimuli (Sequence A). Another set of stimuli was then used to train sequence B. Next, direct training established conditional control of the production of the A sequence and its reversal: in the presence of one printed word, touching the stimuli in the order A1----A2----A3----A4----A5 was reinforced; in the presence of another word, touching the stimuli in the order A5----A4----A3----A2----A1 was reinforced. During probe sessions, the printed words also exercised conditional control over production of the B sequence and its reversal for five of six subjects, suggesting the formation of stimulus classes. Four of these five subjects also performed mixed sequences under conditional control of the words (e.g., A1----B2----A3----B4----A5 and its reversal), verifying that the stimuli which occupied the same position in each sequence were members of the same class.

Spelling and emergent picture-printed word relations established with delayed identity matching to complex samples.

Students with academic deficits learned delayed matching-to-sample tasks that used complex sample stimuli, each consisting of a picture and a printed word. A touch to the sample complex removed it from the computer display and produced either picture comparisons or a choice pool of letters. If the comparisons were pictures, selecting the picture identical to the preceding sample was reinforced. If the letters appeared, letter-by-letter construction of the preceding printed word sample was reinforced. The procedure engendered new constructed-response spelling performances and arbitrary relations among pictures and printed words in matching to sample. The emergence of relations among different sets of printed words (paired with the same pictures) suggested classes of equivalent stimuli. Outcome tests involving spoken words as sample stimuli suggested expansion of subjects' spelling repertoires and stimulus classes.

Generalized oddity performance in preschool children: a bimodal training procedure.

Oddity performance requires relational discriminative responding, which typically is difficult to establish in children with MAs below five. In Experiment 1, a combination intrasubject reversal and multiple baseline across subjects design was used to establish the internal validity of a bimodal intervention in establishing generalized oddity performance. Six of seven children demonstrated oddity responding when presented with stimuli that instantiated the oddity relation in the visual and auditory modalities simultaneously. Oddity performance was evaluated with both reversal assessments and assessments with new sets of stimuli. The newly acquired oddity performance was durable; the six children continued to respond discriminatively when returned to a visual-only task on which they previously had been unsuccessful. Utilizing a reversal assessment more stringent than that of Experiment 1, Experiment 2 replicated this effect. The present studies are the first to demonstrate the utility of bimodal training in establishing oddity performance. The bimodal procedure is discussed with respect to the theoretical positions of Gibson, Dinsmoor, and Dixon.

Constructed-response matching to sample and spelling instruction.

The development of interactive programmed instruction using a microcomputer as a teaching machine is described. The program applied a constructed-response matching-to-sample procedure to computer-assisted spelling instruction and review. On each trial, subjects were presented with a sample stimulus and a choice pool consisting of 10 individual letters. In initial training, sample stimuli were arrays of letters, and subjects were taught to construct identical arrays by touching the matching letters in the choice pool. After generalized constructed-response identity matching was established, pictures (line drawings) of common objects were presented as samples. At first, correct spelling was prompted by also presenting the printed name to be "copied" via identity matching; then the prompts were faded out. The program was implemented with 2 mentally retarded individuals. Assessment trials determined appropriate words for training. Correct spelling was established via the prompt-fading procedure; training trials were interspersed among baseline trials that reviewed and maintained spelling of previously learned words. As new words were learned, they were added to a cumulative baseline to generate an individualized review and practice battery for each subject.

Position-numeral equivalences and delayed position recognition span.

The role of equivalence class formation in delayed position recognition span performance was examined. Initially, the 3 subjects, adults with mental retardation, could not name the nine positions on the span test board. Thus, mnemonic facilitation of span performance based on position naming was not possible. Each subject, however, could name printed numerals and match these stimuli to their dictated names. Matching-to-sample training then established nine equivalence classes, each consisting of a position, a printed numeral, and the numeral name. In subsequent span tests, subject-produced numeral names led to dramatic increases in span scores. The equivalences provided precursors of a kind of verbal code that facilitated performance outside the training context.

Progressive decline of picture naming in an aging Down syndrome man with dementia.

This study was conducted to monitor picture naming longitudinally in a 59-yr.-old Down syndrome man with diagnosed dementia. On the test, the subject was shown a series of 40 pictures, and his task was to speak their names. Correct naming responses were followed by pennies. The test was repeated periodically over the course of 20 mo. The subject initially achieved 100% correct scores and maintained accuracy until the tenth month. Thereafter, his scores declined, gradually at first and then precipitously, until the subject scored less than 30% correct on the final test. Error analysis showed that low scores generally reflected loss of stimulus control by relevant characteristics of the test pictures; control apparently shifted to irrelevant features of the task. The results suggest that naming tests may ultimately prove useful in defining and documenting the nature of deterioration in Down dementia.

Stimulus class formation and stimulus-reinforcer relations.

This study examined stimulus class membership established via stimulus-reinforcer relations. Mentally retarded subjects learned conditional discriminations with four two-member sets of visual stimuli (A, B, C, and D). On arbitrary-matching trials, they selected comparison stimuli B1 and B2 conditionally upon samples A1 and A2, respectively, and C1 and C2 conditionally upon B1 and B2, respectively. On identity-matching trials, they selected all stimuli as comparisons conditionally upon identical stimuli as samples. Throughout training, correct selections of A1, B1, C1, and D1 were followed by one reinforcer, R1, and those of A2, B2, C2, and D2 were followed by another, R2. Subsequent tests documented the formation of two four-member stimulus classes, A1-B1-C1-D1 and A2-B2-C2-D2. The class membership of the A, B, and C stimuli could have been based on equivalence relations that resulted from the arbitrary-matching training. D1 and D2 had never appeared on arbitrary-matching trials, however. Their class membership must have been based on relations with R1 and R2, respectively. Results thus confirm a previous finding that stimulus classes can be expanded via stimulus-reinforcer relations. They also define more precisely the potential nature of those classes and the conditions under which class membership can be established.