It's a dog whistle. There are no studies on this, why would academia (which for the field that would study this is 100% composed of leftists) have a study on leftist dog whistles?
Also, putting any value on "studies" when they almost universally fail to replicate outside of hard sciences is dumb.
Also, putting any value on "studies" when they almost universally fail to replicate outside of hard sciences is dumb.