Hey #linguistics and #language people, I have what might be a very naïve question.

I keep hearing “all languages are equally complex,” but has this actually been tested? What evidence is out there to support this and how is the “complexity” of languages even measured or defined?

I’d be really grateful for recommendations for studies/reviews on this topic. My partner asked me a question about this recently and I realized I was parroting off what I’d heard without really understanding it.