Auditory word recognition processes play a fundamental role in auditory comprehension and are involved in meaning extraction from an acoustic speech signal (Marslen-Wilson & Welsh, 1978). While investigations of auditory comprehension in children are plentiful, there is a dearth of information about children’s development of auditory word recognition. The current thesis was concerned with investigating the developmental trajectories and interactions of component processes involved in auditory word recognition, most notably semantic and cognitive control processes, in school-aged children.
In order to delineate the roles of semantic and cognitive control processes, specifically suppression and attention, on development, a series of real-time priming experiments based on an auditory word repetition paradigm was constructed. By applying systematic experimental manipulations, the aim of these studies was firstly, to investigate top-down lexical activation effects induced by semantic context during auditory word recognition, and secondly, to inform the roles of suppression and attention on activation. While contrasting levels of prime-target relations provided a measure of suppression, tasks with low and high strategic processing requirements were constructed to evaluate the effects of variations in attentional processing. Paired and sentential contextual environments were examined to provide insight into top-down effects with varying levels of contextual support, allowing differentiation between processes induced by specific linguistic relations (lexical or sentential) distinct from general patterns of auditory word recognition. Theoretical models of auditory word recognition were consulted in order to establish experimental predictions. Experimental findings were evaluated both with reference to previous relevant research findings as well as to the theoretical models discussed.
The typical developmental trajectories of component processes of auditory word recognition in children aged 6 to 14 years were firstly examined using paired (n = 20) and sentential (n = 39) auditory word repetition tasks (Chapters 2 and 3, respectively). Active suppression was elicited under some processing conditions, with no developmental differences emerging. Although an increase in processing efficiency with increasing age was evident for all experimental tasks, a greater developmental decrease in naming latencies (NLs) was demonstrated for tasks with higher attentional resource requirements. Additionally, high and low attention-based processing tasks recruited component processes of auditory word recognition differentially, with task-specific priming patterns emerging. Paired auditory word repetition tasks investigating functional and categorical relatedness of prime-target features with varying normative association indicated advantageous processing of functional features in children aged 6 to 8 years, but not in participants aged 8 years and above. This result was in line with theories of semantic development which propose an initial organisation of the mental lexicon based on functional features of lexical representations, with a subsequent hierarchical taxonomic shift (Nelson, 1979). In contrast, no clear developmental patterns emerged in a sentential auditory word repetition task, although context and priming effects did differ with age.
Deficits in cognitive control and semantic processes have been identified in a range of paediatric communication disorders, including those resulting from traumatic brain injury (TBI). Although evidence describing such deficits even after mild TBIs (mTBI) has increased, results have been inconsistent across studies. The current research aimed to elucidate the impact of mTBI on auditory word recognition by evaluating the differential involvement of component processes. Auditory word repetition experiments were replicated with matched cohorts of children aged 8 to 14 years with (n = 11) and without (n = 11) mTBI (Chapters 4 and 5). Participants with mTBI produced longer NLs compared with participants without mTBI for both paired and sentential experimental tasks. Additionally, NLs of participants with mTBI were adversely affected by increasing attentional processing requirements for both paired and sentential tasks. In the paired auditory word repetition tasks, differences in processing between the two participant cohorts depended on the interacting effects of attentional processing with age and the type of semantic feature relation (functional or categorical) being processed. Specifically, these preliminary findings suggested that while typically developing participants evidenced a reduction in NLs from 8-10 to 12-14 year olds in all experimental blocks, participants with mTBI evidenced such a reduction only in the categorically related experimental block with low attentional requirements. This pattern of results was interpreted to indicate that typically developing participants evidenced increased efficiency in attentional processing with increasing age, whereas participants with mTBI exhibited reduced attentional development. In summary, while some developmental changes in semantic processing and suppression crystallised from the current series of experiments, it was the consistent change in attentional processing with age which primarily characterised the development of auditory word recognition in both children with and without mTBI. This finding provided support for the importance of investigating component processes of auditory word recognition in order to identify levels of breakdown and obtain increased knowledge of the role of these processes in general as well as allowing optimisation of clinical management.