Examining the possibilities for volitional character change in compassion and intellectual humility through a three-month online intervention

•A three-month online intervention promoted change in trait and state intellectual humility; however, the intervention only promoted state but not trait compassion.•Enjoying the tasks given to develop intellectual humility predicted increased trait intellectual humility. Moreover, tasks given to develop compassion predicted increased trait compassion.•It is more difficult to change an other-oriented character trait than a non-other-oriented character trait.