Rats can laugh, but the dogs aren’t smiling: they’re hooked on oxytocin, which rises when we lock eyes with one another. Oxytocin is not dissimilar to OxyContin, an opioid analgesic which can result in a similar sense of euphoria or attachment. The oxytocin makes angry faces look less threatening and smiling faces more attractive; still, the important thing to remember about the smiling selfie in your feed is that the person pictured is alone, smiling at themselves. You cannot tickle yourself, Aristotle says, because laughter is a deception: one does not make oneself laugh. We dream alone side by side, but the dream itself is untranslatable, prey to the narrative we impose upon it. Socrates says tickling brings more pain than pleasure, which scientists now call cataplexy, a sudden, temporary paralysis. Rats are ticklish and can’t say no.