Girls are made of sugar and spice and everything nice, but what are boys made of? A randomized control trial suggests the effects of a school-based kindness intervention vary by gender

Abstract

While previous research suggests that kindness interventions in schools can effectively increase kind behaviors, more randomized controlled trials (RCTs) are needed, particularly those examining gender differences. To address this gap, we conducted a matched-pair cluster-RCT with students aged 10–13 in the UK and Spain, analyzing results by gender. The intervention, lasting eight weeks, combined an acts-of-kindness scavenger hunt with weekly journal reflections. Results showed an increase in kindness among girls, but not among boys. Unexpectedly, boys showed increased anxiety following the intervention. This gender difference may stem from the type of kindness promoted—more relational and reflective—which girls may find easier to adopt. It may also relate to girls having more psychological resources for such activities. These findings highlight the need to consider gender-specific responses when designing kindness interventions. They also raise broader questions about how to differentiate character education to ensure it is effective for diverse learners. Addressing these nuances can improve the design and impact of programs aimed at fostering prosocial behavior in young people.