Phonological neighbourhood effects in Italian speech production: Evidence from healthy and neurologically impaired populations.

In two speech production studies conducted in Italian, we investigated the impact of phonological neighbourhood properties such as the neighbourhood density and the mean frequency of the neighbours on speech processing. Two populations of healthy (Study 1) and neurologically impaired (Study 2) individuals were tested. We employed multi-regression methods to analyse naming latencies in Study 1 and accuracy rates in Study 2 while controlling for various psycholinguistic predictors. In Study 1, pictures with words from high-density neighbourhoods were named faster than those from low-density neighbourhoods. Additionally, words with high-frequency neighbours were named faster in Study 1 and yielded higher accuracy rates in Study 2. The results suggest facilitatory effects of both the phonological neighbourhood density and frequency neighbourhood variables. Furthermore, we observed interactions between these two phonological neighbourhood variables and name agreement and repetition. Specifically, the facilitation effect was more pronounced for pictures with lower name agreement and during the initial presentation of the pictures. These findings are discussed in the context of previous literature and within the framework of interactive models of speech production.