There are three types of lacrimation (shedding of tears, or "crying"): basal, reflexive, and psychic. These types of tears can be differentiated by the stimuli that elicit them and their chemical composition. While humans across the world produce psychic tears in response to both positive and negative emotions, and while similar emotions have been identified in other animal species, no reports exist of other animals showing psychic lacrimation.

Basal tears protect and lubricate the eyes, and are produced constantly. Reflexive tears are produced in response to an acute irritant such as dust or dirt. Psychic tears, on the other hand, are produced during strong emotional responses (both positive and negative), and contain more of certain hormones (prolactin, adrenocorticotropic hormone, and leucine enkephalin).