Background and aims The procedural deficit hypothesis attributes the language phenotype in children with specific language impairment to an impaired procedural and relatively intact declarative memory system. The declarative compensatory hypothesis is an extension of the procedural deficit hypothesis which claims that the declarative system in specific language impairment compensates for the procedural deficit. The present study’s aim was to examine the claims of the procedural deficit hypothesis and declarative compensatory hypothesis by examining these memory systems and relation between them in specific language impairment. Methods Participants were children aged 8–13 years, 30 with specific language impairment and 30 typically developing controls, who spoke Kannada (an agglutinating language of the Dravidian family). Procedural learning was assessed using a serial reaction time task. Declarative memory was assessed using two non-verbal tasks that differed at the level of encoding and retrieval: a recognition memory task after incidental encoding using real and novel object images and a recall task after intentional encoding using visual paired associates. Retrieval was examined after short (10 min) and long (60 min) delays after encoding on both declarative tasks. Results Findings confirmed that children with specific language impairment (SLI) have impaired procedural memory on a non-verbal serial reaction time task. On recognition memory task after incidental encoding though children with specific language impairment encoded less well, they recognized items as well as typically developing controls. Both the groups retrieved more at short compared to long intervals and retrieved real (verbalizable) objects better than novel objects. On visual paired associates (recall task with intentional encoding) children with specific language impairment retrieved less than typically developing children (even after controlling for non-verbal ability and age). Furthermore, across retrieval types of declarative tasks, although children with specific language impairment did less well than typically developing, their pattern of performance was comparable to typically developing children. Finally, the correlation between memory systems did not support a trade-off between memory systems in children with SLI as predicted by the compensatory wing of procedural deficit hypothesis. Conclusions The findings supported the major claim of the procedural deficit hypothesis – a procedural learning deficit in specific language impairment and an intact declarative system, however, only if measured on task that was designed to be undemanding. Furthermore, there was no evidence for a trade-off between these systems. Implications and future directions Some interventions with specific language impairment use explicit teaching of grammar, an approach that uses the declarative rather than the procedural system. Our findings cast doubt on whether this is likely to be the most effective strategy.

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Statistical learning has been proposed as a key mechanism in language learning. Our main goal was to examine whether adults are capable of simultaneously extracting statistical dependencies in a task where stimuli include a range of structures amenable to statistical learning within a single paradigm. We devised an online statistical learning task using real word auditory–picture sequences that vary in two dimensions: (i) predictability and (ii) adjacency of dependent elements. This task was followed by an offline recall task to probe learning of each sequence type. We registered three hypotheses with specific predictions. First, adults would extract regular patterns from continuous stream (effect of grammaticality). Second, within grammatical conditions, they would show differential speeding up for each condition as a factor of statistical complexity of the condition and exposure. Third, our novel approach to measure online statistical learning would be reliable in showing individual differences in statistical learning ability. Further, we explored the relation between statistical learning and a measure of verbal short-term memory (STM). Forty-two participants were tested and retested after an interval of at least 3 days on our novel statistical learning task. We analysed the reaction time data using a novel regression discontinuity approach. Consistent with prediction, participants showed a grammaticality effect, agreeing with the predicted order of difficulty for learning different statistical structures. Furthermore, a learning index from the task showed acceptable test–retest reliability (r = 0.67). However, STM did not correlate with statistical learning. We discuss the findings noting the benefits of online measures in tracking the learning process.

The procedural deficit hypothesis (PDH) claims that language deficits in children with specific language impairment (SLI) are caused by sequence learning deficits. Previous studies provided evidence that were both in favor and against this hypothesis. Few studies reported on sequence learning pattern in SLI children using various modifications of the serial reaction time (SRT) task. The present study aimed to examine the PDH by examining sequence learning pattern in SLI using an adapted SRT task. The study also examines the sequence learning pattern among typically developing and SLI children. Results are discussed with relevance to sequence learning pattern and language deficits in SLI children.