Full disclosure, I find behavioural research fascinating, though I know it isn't everyone's cup of tea (with a cup of tea not being everyone's cup of choice).
This research from the Behavioural Insights Team on a small tweak people can make to how they represent their experience certainly got my interest. Run as a properly randomised control trial to more than 9000 real-world job vacancies comparing four equivalent CVs and cover letters, with the following alterations:
Currently employed: No gap.
Explained gap: 2.5-year gap since last job explained for childcare
Unexplained gap: 2.5-year gap since last job left unexplained
No dates: Dates of employment history replaced with the number of years’ experience
A 2% call back difference for CVs with and without gaps was not statistically significant but a 14.6% positive increase in call backs where experience was expressed in years was really noteworthy.
Research available here: https://www.bi.team/blogs/can-one-line-on-a-cv-support-people-back-into-work/