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The majority of the world are bilingual, consequently research into the effects of bilingualism on cognition is well established. Specifically, research has focused on the potential advantage bilingualism could convey to executive functions, defined as a group of cognitive processes implicated in planning, managing and executing goals. It is argued that the demands of using two or more languages affords bilinguals more opportunities to ‘train’ certain EFs, resulting in enhanced performance compared to monolingual peers. However, research has only investigated this relationship in neurotypical populations. Given the executive dysfunction hypothesis of autism, and the hypothesised link between autistic traits and poorer executive functioning, it would be of interest to understand whether the findings that bilingualism conveys EF advantages in a neurotypical population can be extended to a population with a clinical ASC diagnosis. There is a limited amount of research investigating bilingualism and EF in an autistic population, which is further restricted by small, child samples. This is particularly problematic on account of research to suggest that EF performance varies with age and the effects of bilingualism may be more or less apparent during the development of EF in childhood, thus the findings of the few studies that do exist cannot be reliably extended to an adult population. Therefore, these two studies will explore the effects of bilingualism on EF performance in an adult population. Study 1 will recruit an entirely neurotypical population with varying degrees of autistic traits as measured by the Broad Autism Phenotype Questionnaire (BAPQ). Using a neurotypical sample is appropriate given that autism occurs on a spectrum and thus the associated characteristics are present in a nonclinical population. Furthermore, autism symptom severity has been associated with greater EF dysfunction in neurotypical populations. Thus, understanding the potential impact of bilingualism for neurotypicals with high autistic traits is important and will provide valuable data that may elucidate the relationship between autism severity and EF performance. In Study 2, both neurotypicals and individuals with a clinical diagnosis of ASC will be recruited. Additionally, neurotypicals must score under 108 (clinical cut off score) on the BAPQ. It is imperative to implement this criterion as it ensures that the two groups are sufficiently distinct on the variable that is defining the groups (autism diagnosis or not). Furthermore, given the data to suggest a correlation between autism symptom severity and poorer EF performance in a neurotypical population, it is important to exercise this restriction in order to allow for a greater comparison between groups. The analyses run will help to elucidate the relationship that bilingualism and autism have on EF performance, with particular interest in investigating whether bilingualism in an autistic adult population is a protective factor of certain EF skills.

The interplay of bilinguals' languages during visual written word recognition was investigated using a novel set of Spanish (L1) – English (L2) interlingual homographs, which are words ambiguous cross-linguistically. Differently from previous literature, both identical (e.g., PIE, meaning foot in Spanish) and near-identical (e.g., CARPET, with CARPETA meaning folder in Spanish) interlingual homographs were \ud considered and a database was created to allow for an easy-accessible list of stimuli including their associated linguistic characteristics in both languages. A series of studies were conducted in the participants' L2 at both the lexical and the semantic level to explore the extent of the non-target L1's activation and the role of cross-linguistic \ud orthographic overlap. Study 1’s findings showed that L1 linguistic properties significantly predicted bilinguals' performance in lexical decision task. In Study 2 \ud interlingual homographs were used as primes and inserted at the end of sentences biased to the L2 reading; and were followed by targets related to either the Spanish, English, or unrelated to either meaning. Prime duration was manipulated to explore late (500ms; Study 2a) and early (200ms; Study 2b) stages of processing. Bilinguals showed \ud significant negative priming for the Spanish-related meaning in the 500ms prime condition but not in the 200ms. Overall, Study 1 and 2 found no significant processing differences between identical and near-identical homographs. \ud Study 3, instead, investigated within-language ambiguity by using homonyms, which, like interlingual homographs, have the same word form but different meanings. Like Study 2, homonyms were placed at the end of sentences biased to the non-dominant meaning and stimuli were created to mimic near-identical interlingual homographs. Native English speakers produced significant priming for the sentence-relevant meaning only, irrespective of whether meaning activation was probed at early or later processing stages, thus suggesting a swift resolution of ambiguity in L1.\ud Findings are discussed with reference to existing models of the bilingual lexicon (e.g., BIA+ model, Dijkstra & van Heuven, 2002). In particular, evidence of the activation of the non-target L1 was found (i.e., Studies 1b and 2a) which supports the idea of non-selective access.