No: (a) the t-shirts probably also work without me pointing to them, and (b) me noticing that the shirt has the answer is an instance of the phenomenon I describe.
a) Fair enough b) Do you really need that, or does it just feel nice to see it? If they weren't wearing the t-shirt would you really not think of it? If I put up a poster in my kitchen saying "Eat!" then I would often notice it when it's completely relevant, but that doesn't mean it's a useful poster.
