For the past 30 years, researchers have come to an agreement on personality traits developing throughout the lifespan, especially in early adulthood between 20 and 60 but even into old age (Roberts & Mroczeak, 2007). While there are individual differences, mean level changes of personality traits show a positive trend. This means people become more dominant, confident, warm, responsible, and calm, on average. They often become more planful, productive and involved contributors to society, something that some have described as social maturation (Roberts & Woods, 2006, Caspi et al. 2005). However, firstly, most of the research has looked at mean level change in personality traits on a domain level the Five-Factor Model/ Big Five, which bundles traits into Agreeableness, Consciousness, Neurotism/ Negative Emotion, Openness to Experience and Extraversion. However, age differences are better predicted by more specific traits such as facets and nuances (Mõttus et al, 2020), showing that not all facets and items of one domain develop in the same direction, sometimes even towards opposite ends (Schwaba et al.2022, Bleidorn et al., 2009; Costello et al., 2017; Klimstra et al., 2018; Soto & John, 2012; Terracciano et al., 2005). However, there has been very little research looking at these more specific changes in personality traits. Secondly, the maturation principle of average trait changes is widely accepted but rarely formally tested (Schwaba et al 2022). Therefore, this study will use a list of 198 items which have been selected from the IPIP item pool by Mõttus & Henry. These items have been tested for reliability and consensual validity, and have been argued to be a useful inventory for nuances. After a definition of personality maturity has been derived based on the opinions of the experts in the field of personality development, these 198 items will be rated by a lay audience according to the definition in terms of how much they reflect personality maturity. In the next step, items' average maturity ratings will be compared to their correlations with age obtained in different data, expecting a positive correlation so that items rated as reflecting higher maturity show a positive correlation with age, items rated low on maturity show a negative correlation with age, and items rated neither low nor high in maturity show no age differences. Lastly, Ausmees et al. (2022) found that social desirability plays a significant role in self-ratings. Traits that seem socially desirable and age differences in them were often amplified in self-ratings when comparing them to informants' ratings. As maturity may be argued to be confounded with social desirability, we will test if the correlation between traits' age differences and maturation ratings remains significant, controlling for items' social desirability as rated by a separate sample. This is arguably even more interesting as this study will only use self-reported data. As we have got social desirability ratings of the items available already available, this will data will be compared to the data collected in terms of maturity.