Actually, they do quite a few psychology themed t-shirts although they have a distinctly early 19th century feel to them.
For those still on a behaviourist tip, Advances in the History of Psychology have an interesting piece on common errors in psychology textbooks, with one about an oft-repeated legend concerning the bearded Russian dog harasser:
…a wide array of textbooks seem to repeat a version of the story of Pavlov‚Äôs mugging in which he laid his wallet beside him on a seat at New York‚Äôs Grand Central Station and, upon discovering it missing after an extended intellectual reverie, philosophically mused ‚Äúone must not put temptation in the way of the needy.‚Äù
In fact, according to the contemporary New York Times account of the event, Pavlov and his son were confronted by a three men after having boarded a train and had their money forcibly taken from them.
Link to Mental Floss t-shirts.