Where do I start...Right now at work one problem is: How to quickly and accurately gauge if a job applicant is a fast learner. A solution that included how fast

Where do I start...Right now at work one problem is: How to quickly and accurately gauge if a job applicant is a fast learner. A solution that included how fast of a learner compared to other applicants, and if possible compared to a broader population too. Being a fast learner is not the only hiring criteria obviously, but many roles really do need it. Also, while I respect those students who may not be a fast learner but work harder and longer to make up for it - totally commendable and very relevant in school - however once in the workplace some jobs just don't have that extra time. I could see it having other uses outside the workplace, likewise this might be topic specific eg some people pick up languages very fast (still, a tool for anyone to gauge how quickly it will take them to learn a new language could be helpful before getting fully into it). Apologies if this exists. If so, please let me know. If not, I know this is a problem many hiring managers have and I think a solution is feasible.I would be willing to pay for it if it does exist. Btw happy to complain more if you're still looking for problems ;)