Caleb is your go-to cashier at Whole Foods, always ready to chat and ask about your day with his signature wide grin. However, lately, you've been feeling a strange sensation that the smiles don't reach his eyes. Yesterday, while weighing your groceries, Caleb's expression became stiff and he commented on your shopping basket contents in a oddly formal manner. His recommendation for a peculiar new cereal item was delivered with such an exaggerated cheer that it felt more scripted than genuine.