Research reported here concerns neural processes relating to stimulus equivalence class formation. In Experiment 1, two types of word pairs were presented successively to normally capable adults. In one type, the words had related usage in English (e.g., uncle, aunt). In the other, the two words were not typically related in their usage (e.g., wrist, corn). For pairs of both types, event-related cortical potentials were recorded during and immediately after the presentation of the second word. The obtained waveforms differentiated these two types of pairs. For the unrelated pairs, the waveforms were significantly more negative about 400 ms after the second word was presented, thus replicating the "N400" phenomenon of the cognitive neuroscience literature. In addition, there was a strong positive-tending wave form difference post-stimulus presentation (peaked at about 500 ms) that also differentiated the unrelated from related stimulus pairs. In Experiment 2, the procedures were extended to study arbitrary stimulus-stimulus relations established via matching-to-sample training. Participants were experimentally naïve adults. Sample stimuli (Set A) were trigrams, and comparison stimuli (Sets B, C, D, E, and F) were nonrepresentative forms. Behavioral tests evaluated potentially emergent equivalence relations (i.e., BD, DF, CE, etc.). All participants exhibited classes consistent with the arbitrary matching training. They were also exposed also to an event-related potential procedure like that used in Experiment 1. Some received the ERP procedure before equivalence tests and some after. Only those participants who received ERP procedures after equivalence tests exhibited robust N400 differentiation initially. The positivity observed in Experiment 1 was absent for all participants. These results support speculations that equivalence tests may provide contextual support for the formation of equivalence classes including those that emerge gradually during testing.

No abstract

Results suggest that some children with DS can improve their auditory verbal memory span with home-based rehearsal training, at least in limited ways. Children with good language and verbal working memory skills may be the best candidates for this type of training, even though they may show only small improvements. Still, small improvements in a severely impaired function are noteworthy, and justify further investigation.

Researchers in recent years have made much progress towards understanding why some children struggle to learn to read. However, little of this research has involved children with intellectual disability associated with an IQ < 70 (ID, also called mental retardation). In the present analysis, the authors examined cognitive similarities and differences between stronger and weaker decoders, all of whom have ID. The 65 children with ID in the present analysis were initially referred by their teachers for a study that involved training basic phonological reading skills. The present analysis compares 21 children who were excluded from the training study because their decoding skills were already too high with 44 children whose decoding skills were low enough for the training study. The groups were compared on general intelligence, language ability, phonemic awareness and phonological memory. Initial analyses showed that the stronger decoders were significantly better than weaker decoders in language ability, phonemic awareness and rehearsal in phonological memory, but not in intelligence. They were also significantly older than weaker decoders. When age was covaried out, the groups differed significantly only in rehearsal in phonological memory, although the difference for phonemic awareness was marginally significant when the poorest performers were excluded. When intelligence is substantially limited, the ability to rehearse or refresh phonological codes in working memory plays a major role in determining children's success in learning to read. This ability appears to be more important than intelligence, language ability and phonemic awareness. It is possible that the reason the phonemic awareness measure was not as good at distinguishing the groups as the phonological rehearsal measure was because the former did not involve assembling phonological output. It is suggested that it is the combination of poor phonological representation and poor phonological output assembly that makes decoding difficult for some children with ID.

No abstract