Harrie Boelens

A Traditional Account of Stimulus Equivalence

A three-term contingency account of stimulus equivalence is presented. The performances of stimulus equivalence are interpreted as instances of generalized performances. It is assumed that the generalized performances are caused by reinforcement histories in the usual environments of humans. The present account differs from the account proposed by Hayes and Hayes (1989) with regard to the nature of the responding brought about by the reinforcement histories and with regard to the role of context.

A computer-based system providing pictorial instructions and prompts to promote task performance in persons with severe developmental disabilities

This study was aimed at assessing a new computer-based system to promote task performance in three adults with severe developmental disabilities. The new system, which was small and battery powered, could provide auditory and vibratory prompts in addition to pictorial instructions concerning the task steps. To control for the effects of the computer-based system, the subjects were also exposed to a card system. The results showed that the subjects had a significantly higher level of correct performance on the tasks presented with the computer-based system than on the tasks presented with the card system. Two of the subjects, moreover, seemed to prefer the computer-based system to the card system.

Habit-reversal treatment for children's stuttering: assessment in three settings.

Two boys (9 and 14 years old) participated in an evaluation of treatment for stuttering. Habit reversal procedures (awareness training, regulated breathing, and social support) were combined with teaching positive attitudes to parents. During treatment, stuttering frequencies decreased, speech rates increased, and speech naturalness ratings increased. These changes occurred in the clinic, the childs home, and the childs school. After treatment, stuttering remained low in the clinic and at home, but increased stuttering was found at school.

Object interference in children's colour and position naming: Lexical interference or task-set competition?

Cascade models of word production assume that during lexical access all activated concepts activate their names. In line with this view, it has been shown that naming an objects colour is facilitated when colour name and object name are phonologically related (e.g., ‘blue’ and ‘blouse’). Prevor and Diamonds (2005) recent observation that children take longer to name the colour of real objects than of abstract forms could also be attributed to cascaded processing, resulting in competition between colour name and object name. Experiments 1 and 2 replicate this ‘object-interference effect’ in colour naming by children of 5–7 years of age and show that it generalises to position naming. Experiment 2 shows that the effect is also obtained with hard-to-name objects; a finding that is at variance with a lexical-competition account. The finding in Experiment 3 that the object-interference effect is absent in adults, is consistent with an alternative interpretation in terms of task-set competition. Implications for models of word production are discussed.

Symmetric Matching to Sample in 2-Year-Old Children

The emergence of symmetric matching to sample was studied in fourteen 2-year-old children. Three two-choice, arbitrary matching-to-sample tasks were arranged successively. Each task was followed by a test of symmetric responding. The behavior required by the tasks was taught with sample stimulus-control shaping (Zygmont, Lazar, Dube, & McIlvane, 1992). Five children did not learn identity matching, which is required for sample stimulus-control shaping. Two others showed a deterioration of baseline responding when the first test was given. The participation of these seven children was stopped. The others showed symmetric responding on all tests. These results demonstrate generalized symmetric matching to sample (one aspect of stimulus equivalence) in 2-year-old children.

Studying Stimulus Equivalence: Defense of the Two-Choice Procedure

Sidman (1987) and Carrigan and Sidman (1992) have advised against the use of two-choice procedures in studies of emergent matching to sample. They argue that in two-choice, as opposed to multiple-choice, procedures: (1) It is more difficult to make sure that the baseline conditional relations have been established; (2) There is a greater chance that test outcomes are not related to the baseline conditional relations; and (3) The predictions of stimulus equivalence are less clear. In response to the first two arguments, I argue that they refer to technical difficulties that can easily be handled within the two-choice procedure itself. In response to the third argument, I argue that the formulation of Carrigan and Sidman is a new account, that it is inconsistent with the old account of Sidman and Tailby (1982), and that the two-choice procedure goes well with the old account. Further, I argue that there are no strong reasons for adopting the new account, and that the recommendation of using three choices in particular is problematic.

Influencing Children’s Symmetric Responding in Matching-to-Sample Tasks

A multiple-exemplar account of symmetric matching to sample was tested with 5- to 6-year-old children. Each child went through five similar phases. Each phase began with a two-choice arbitrary matching-to-sample task. This was followed by a test of symmetric responding. The first four phases ended with training of symmetric or asymmetric responding. This differed between two groups of 10 children. For example, after conditional relations A1B1 and A2B2 had been trained, and symmetry had been tested, conditional relations B1A1 and B2A2 (Group Symmetric) or B1A2 and B2A1 (Group Asymmetric) were trained. The stimuli differed between phases. Symmetric responding increased as a function of tests in Group Symmetric; it decreased in Group Asymmetric. These findings support a multiple-exemplar account of stimulus equivalence.

Emergent simple discrimination in children: role of contiguity

Sixteen five- to seven-year-old children were exposed to two colour-form compounds. The compounds were presented successively. Pointing to the compounds was reinforced. Eight children received compounds A1B1 and A2B2; the others A1B2 and A2B1. This task was mixed with a two-choice discrimination task that provided the colours A1 and A2 simultaneously. Colour A1 was correct for four children in each group. Finally, tests were given that offered a choice between forms B1 and B2, without A1 or A2. The children preferred the form that had been paired with the correct colour of the two-choice discrimination task. The results can be explained with the assumption that functions transfer between stimuli if the stimuli occur contiguously. This assumption also accounts for transfer of functions between stimuli paired in matching-to-sample tasks.

Errorless Discrimination of Reversible Letters: Superimposition and Fading Combined With an Intervening Response

Two experiments were carried out to assess errorless training procedures for the discrimination of reversible letters (i.e., b and d). The first procedure consisted of superimposition and fading concerning the S+. The second procedure was the same as the first one except that it also involved an “intervening” response. The third procedure differed from the second in that two prompts, varying only in orientation, were superimposed on the S+ and S−. Experiment 1 included 27 normal 4- to 5-year-old children. Experiment 2 included 27 mentally retarded students whose chronological and mental ages averaged 11.2 and 5.2 years, respectively. The results of the two experiments were comparable. Superimposition and fading alone was ineffective. The second procedure was not significantly better despite the intervening response. The third procedure, however, was highly effective. Theoretical and practical aspects of the findings are discussed.

Functional Assessment of School Attendance Problems: An Adapted Version of the School Refusal Assessment Scale-Revised.

The School Refusal Assessment Scale (SRAS) was developed to identify four factors that might maintain a youth’s school attendance problem (SAP), and thus be targeted for treatment. There is still limited support for the four-factor model inherent to the SRAS and its revision (SRAS-R). Recent studies indicate problems with the wording of eight items added to the SRAS to form the SRAS-R. We examined the factorial validity of an adapted item set comprising 16 of the 24 SRAS-R items and eight items developed for this study. The eight items paralleled the content of the SRAS-R items being replaced but were less complex and ambiguous. Data were gathered from 199 youth with a SAP and 131 parents. Confirmatory factor analysis (CFA) of the adapted item set supported a four-factor model. Internal consistency reliability of the subscales was higher than it is commonly reported in SRAS-R studies. Concurrent validity was supported by associations between the four factors and measures of internalizing or externalizing behavior. The adapted SRAS-R may help professionals reliably assess the relative strength of factors maintaining SAPs. This is one of the few studies conducted independent of the instrument’s developer and in a school culture different from that where the instrument is usually tested.