Why Are Causal and Temporal Connectives Difficult to Understand? A Comparison Between Italian Hearing Good and Poor Comprehenders and Deaf Poor Comprehenders

Purpose: Both hearing poor comprehenders (PCs) and deaf or hard-of-hearing (DHH) PCs have problems in understanding causal and temporal coherence relations signaled by connectives. The study examined whether hearing and DHH PCs' problems with connective understanding are similar and mainly related to their limited vocabulary, including knowledge of connective words, or to their poor reading comprehension abilities more generally. Method: Three groups of 7- to 10-year-old readers, matched on grade level (hearing PCs, DHH PCs, and hearing good comprehenders [GCs]) performed a reading comprehension task, a vocabulary task, and causal and temporal connective understanding tasks. Hearing and DHH PCs were also matched on reading comprehension and decoding abilities. Results: The DHH PCs performed significantly worse than both the hearing GCs and PCs in temporal and causal connective understanding. Significant differences between hearing PCs and GCs were found only in causal connective understanding. DHH readers' difficulties in causal connective understanding were significantly associated with poorer vocabulary knowledge. In contrast, vocabulary knowledge did not uniquely contribute to hearing PCs' difficulties with causal connective understanding, once their reading comprehension skills were controlled for. Conclusions: The results suggest that despite a similar reading profile, DHH PCs' difficulties with causal connective understanding are more closely related to their vocabulary delay, whereas hearing PCs' difficulties are more strongly influenced by their poor text integration processes (as indexed by their reading comprehension skills). Neither vocabulary knowledge nor reading comprehension skills contributed to the explanation of DHH readers and hearing PCs' temporal connective understanding.