"Ability" by itself is a bit vague here, but I will say that having a proven trackrecord in their ability to learn is something I specifically look for in a candidate. Not only learning new tech, but also learning from mistakes and experiences over time.
However, I don't think raw "intelligence" is the right metric for hiring. Unless you specifically mean emotional intelligence, which can curtainly contribute to improving communication skills on the team.
I've also found that when hiring someone with mostly expertise outside your current stack it's critical to provide good feedback loops and mentoring early on so they can "get up to speed" and contributing valuable, idiomatic code as fast as possible without feeling as though your entire onboarding experience is trial by fire. This mentoring takes up extra resources and is a net drain on your team in the short term, but pays off in the long term.
However, I don't think raw "intelligence" is the right metric for hiring. Unless you specifically mean emotional intelligence, which can curtainly contribute to improving communication skills on the team.
I've also found that when hiring someone with mostly expertise outside your current stack it's critical to provide good feedback loops and mentoring early on so they can "get up to speed" and contributing valuable, idiomatic code as fast as possible without feeling as though your entire onboarding experience is trial by fire. This mentoring takes up extra resources and is a net drain on your team in the short term, but pays off in the long term.