Personality Change in the Light of Relationship Transitions in Partnered and Single Individuals (PINIE)

Young adults aged 18–40, proficient in German, and either single or in a romantic relationship (of 1 to 24 months) at study entry; ownership of a smartphone with Internet access was required.

Non-probabilistic sampling using targeted online recruitment (social media: Facebook, Instagram, TikTok, Reddit; mailing lists; flyers; university lectures) and quota sampling (towards the end of the recruitment phase, only people in relationships were accepted, as the target quota for singles had already been reached). Inclusion criteria: aged 18–40, single or in a relationship of 1–24 months, German language skills, smartphone with internet access.

Of the 2,072 individuals who provided informed consent, 291 were excluded, resulting in a final sample size of N = 1,781. Of these, 32.4% completed all seven waves; on average, M = 4.08 waves were completed (SD = 2.78).