BA doesnt recovery heavy math, and stem courses, unlike a BS degree. i looked at a BA and bs for bio, bio required a ton more lab and science cours, and chem, ochem, biochem. but ba might not require all of those. for psych its almost always BA, unless your doing a PHD in the future. PSY-D might only need a BA.

TIL it can be either?

From looking it up, it's usually a BA, but it can be a BS depending on focus.