This study investigated effects of healthy ageing and of non-verbal attentional control on speech production. Young and older speakers participated in a picture-word interference (PWI) task with compound targets. To increase the processing load, the two pictures of the compounds' constituents were presented side-by-side for spoken naming (e.g., a picture of a sun + a picture of a flower to be named with sunflower). Written distractors either corresponded to the first or second constituent (sun or flower → sunflower), or were semantically related either to the first constituent of the target (moon → sunflower) or to the second constituent/whole word (tulip → sunflower). Morpho-phonological facilitation was obtained for both constituents, whereas semantic interference was restricted to first-constituent-related semantic distractors. Furthermore, a trend towards facilitation was obtained for distractors that were semantically related to the whole word. Older speakers were slower and produced more errors than young speakers. While morphological effects of first-constituent distractors were stronger for the elderly, the semantic effects were not affected by age. Non-verbal attentional control processes, measured in the Simon task, significantly contributed to morpho-phonological priming in the elderly, but they did not affect semantic interference or semantic facilitation. With a picture naming task that increases the semantic and lexical processing load, we corroborate earlier evidence that word-finding difficulties in the elderly result from deficient phonological encoding, whereas lexical-semantic and morpho-phonological representations remain stable with age.
Keywords: Noun-noun compounds; ageing; attentional control; morphological facilitation; picture-word interference; semantic interference.