Development and vulnerability across the lifecourse.

What is it that develops in adult life? Development through work and family life have been documented and theorised in detail, but much less is known about what is learned beyond these domains, through people's engagements in hobbies or when out of work (e.g., unemployed, retired). We argue that adult development can be addressed in general terms, beyond domain specificity; drawing on our sociocultural psychology framework, and assuming an open-system perspective, we highlight the two processes of progressive differentiation and psychological distancing in diverse domains of activity. To address development over time, we explore 20 years of people's lives through the longitudinal analysis of online diaries. A combination of quantitative and qualitative analysis enables us to identify people's experiences of rupture and transitions, the diversity of their domains of interests, and how these change over time. Based on a case-study, we show that, if the general direction of development does entail progressive differentiation and distanciation, these processes can also be hindered by the cumulation of vulnerabilising events. Finally, we show that some domains, such as the long-standing activity of diary writing, can itself be used as resource for adult development.