was discovered and adopted by Sigmund Freud. Schopenhauer's tale was quoted by Freud in a footnote to his 1921 work Group Psychology and the Analysis of the Ego (). Freud stated, of his trip to the United States in 1909: "I am going to the USA to catch sight of a wild porcupine and to give some lectures." Social psychological research The dilemma has received empirical attention within the contemporary psychological sciences. Jon Maner and his colleagues (Nathan DeWall, Roy Baumeister, and Mark Schaller) referred to Schopenhauer's "porcupine problem" when interpreting results from experiments examining how people respond to ostracism. The study showed that participants who experienced social exclusion were more likely to seek out new social bonds with others. In popular culture The parable of the hedgehog's dilemma has been referenced in several works of media, including the show Neon Genesis Evangelion. The award-winning short film Henry is a modernist version of the hedgehog's dilemma: in this story, the hedgehog eventually finds social comfort through a turtle, that is, a fellow social creature who is invulnerable to the hedgehog's spines. In the context of the original dilemma, this can be taken to represent the need for variability in human social preferences. The Japanese vocaloid song Harinezumi by Tota Kasamura is about the Hedgehog's dilemma. See also List of paradoxes Social isolation References Arthur Schopenhauer Interpersonal relationships Dilemmas Hedgehogs in popular culture Metaphors referring to animals Philosophy of life