Pronunciation is a product of many factors. The constituent factors you decide on as being the most relevant such as language aptitude can be measured by other factors such as verbal ability, auditory ability, motivation etc. The relationship between foreign language aptitude and intelligence requires further research and some core concepts may need redefining.
A classic from 1965:
Language aptitude, intelligence, and second-language achievement.
"This study demonstrates that
measures of intelligence are relatively independent of both language aptitude and 2nd-language achievement, and moreover, that different 2nd-language skills are related to different abilities."
http://psycnet.apa.org/index.cfm?fa=buy.optionToBuy&id=1965-15290-001One Intelligence or Many? Alternative Approaches to Cognitive Abilities
http://psych.utoronto.ca/users/reingold/courses/intelligence/cache/paik.htmlThe Illusory Theory of Multiple Intelligences
https://www.psychologytoday.com/blog/unique-everybody-else/201311/the-illusory-theory-multiple-intelligencesThe Relationship of Three L2 Learning Factors with Pronunciation Proficiency: Language Aptitude, Strategy Use, and Learning Context
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Results indicated that general language aptitude did not predict pronunciation gains regardless of type of setting (ESL or EFL),
but that auditory aptitude may be linked to pronunciation proficiency. Analyses revealed that specific
pronunciation strategies were strong predictors of pronunciation gain for comprehensibility and accuracy gains. The findings for this study suggest that pronunciation strategies seem to play a bigger role in pronunciation improvement than language aptitude and are effective in both ESL and EFL settings."
"Because aptitude is grounded in a learner‘s natural intelligence and strategies are a product of behavior, one purpose of this research was to assess the gap in understanding which of these two factors is more influential or a more important predictor of L2 learning ability. Although aptitude, learning strategies and learning context have been influential in predicting L2 proficiency, there are currently no known studies that have examined the simultaneous impact of aptitude and strategy use in relation to pronunciation gains and English learning context.
In fact, the little research that has been done regarding L2 oral proficiency suggests that ESL learners have a greater advantage in acquiring these skills than EFL learners because of the native English learning context."
"The relationship between language aptitude and pronunciation accuracy theoretically should exist, but practically, the study by Baker Smemoe and Haslam (2013) indicates that it is rather weak. It may be considered stronger if additional components of language aptitude are taken into consideration, namely motivation and auditory aptitude."
http://scholarsarchive.byu.edu/etd/2111/The Effect of Language Learning Aptitude, Strategy Use and Learning Context on L2 Pronunciation Learning
The findings for this study suggest that learning context plays a limited role in strategy use and that aptitude affects pronunciation accuracy and pronunciation strategies affect comprehensibility. Thus, strategy and aptitude affect different aspects of pronunciation.
http://applij.oxfordjournals.org/content/34/4/435Literature review on musical aptitude and language aptitude
"The relationship between language aptitude and pronunciation accuracy is rather difficult to establish since sparse studies have been conducted in the area. Language aptitude is a person’s potential to acquire a foreign language. This does not mean that a person with low language aptitude will not learn a foreign language, but that they will most probably do it with more difficulty and at a slower pace than a person with high aptitude. However, even though language aptitude should facilitate pronunciation accuracy by definition (language acquisition entails its pronunciation acquisition),
standardised tests measuring language aptitude do not test speech production. As Hinton (2013: 104) notes, none of the commonly used aptitude tests ...require the testee to produce speech. Thus, neither speech nor its phonetical and phonological aspects can be assessed by means of existing aptitude tests...
The relationship between language aptitude and pronunciation accuracy theoretically should exist, but practically, the study by Baker Smemoe and Haslam (2013) indicates that it is rather weak. It may be considered stronger if additional components of language aptitude are taken into consideration, namely motivation and auditory aptitude...
The influence of musical aptitude on foreign language pronunciation accuracy has been the most extensively researched relationship among the ones being the subject of this paper. Multiple studies have been conducted in the area, their results being inconclusive since some of them confirm, while others reject the existence of a link between musical talent and L2 sound acquisition."
http://ojs.edukacja.wroc.pl/index.php/GRE/article/viewFile/131/139Melodies that Help: The Relation between Language Aptitude and Musical Intelligence
https://papers.ssrn.com/sol3/papers.cfm?abstract_id=1815339Sensory discrimination as related to general intelligence
http://scholarworks.rit.edu/cgi/viewcontent.cgi?article=2089&context=article