{"id":{"repo_id":"essex","oai_identifier":"oai:repository.essex.ac.uk:20189"},"canonical_url":"https://search.dev.ndltd.org/etd/essex/oai:repository.essex.ac.uk:20189","repository":{"repo_id":"essex","name":"University of Essex","base_url":"https://repository.essex.ac.uk/cgi/oai2"},"display":{"title":"The Discordant Development of Sexual Orientation in Identical Twins","abstract":"The present thesis investigated how genetically identical twins with discordant sexual orientations differed in correlates of their sexual orientation in order to understand to what degree non-genetic factors affect the formation of sexual orientation. Because identical twins share 100% of their genes, factors other than genetics may contribute to any differences within these pairs. Chapter 1 gives an overview of the literature. Chapter 2 focuses on childhood gender nonconformity (femininity in males, masculinity in females), which predicts a non-straight (gay, lesbian, or bisexual) sexual orientation in adulthood. In order to avoid the limitations of self-report measures, gender nonconformity of these twins was assessed via observer ratings of their photographs from childhood and adulthood. In addition, although genetically identical twins can differ in their self-reported sexual orientations, it is unclear to what degree these self-assessments reflect observable differences in sexual arousal such as genital response or pupil dilation patterns while viewing sexual stimuli. Chapter 3 focuses on these responses in identical twin pairs with discordant sexual orientations. Finally, differing intrauterine environments during the early development could result in a discordant development of sexual orientation in identical twins. This includes varied prenatal hormonal exposures between twins. Chapter 4 highlights a putative biomarker of early hormonal exposure: the ratio of index to ring finger length (2D:4D), within these twin pairs In combination, findings suggested that these twins differed in many (but not in all) correlates of their sexual orientation, suggesting non-genetic influences. However, there were also subtle similarities within pairs that pointed to potential familial (e.g., genetic) influences.","abstract_html":"The present thesis investigated how genetically identical twins with discordant sexual orientations differed in correlates of their sexual orientation in order to understand to what degree non-genetic factors affect the formation of sexual orientation. Because identical twins share 100% of their genes, factors other than genetics may contribute to any differences within these pairs. Chapter 1 gives an overview of the literature. Chapter 2 focuses on childhood gender nonconformity (femininity in males, masculinity in females), which predicts a non-straight (gay, lesbian, or bisexual) sexual orientation in adulthood. In order to avoid the limitations of self-report measures, gender nonconformity of these twins was assessed via observer ratings of their photographs from childhood and adulthood. In addition, although genetically identical twins can differ in their self-reported sexual orientations, it is unclear to what degree these self-assessments reflect observable differences in sexual arousal such as genital response or pupil dilation patterns while viewing sexual stimuli. Chapter 3 focuses on these responses in identical twin pairs with discordant sexual orientations. Finally, differing intrauterine environments during the early development could result in a discordant development of sexual orientation in identical twins. This includes varied prenatal hormonal exposures between twins. Chapter 4 highlights a putative biomarker of early hormonal exposure: the ratio of index to ring finger length (2D:4D), within these twin pairs In combination, findings suggested that these twins differed in many (but not in all) correlates of their sexual orientation, suggesting non-genetic influences. However, there were also subtle similarities within pairs that pointed to potential familial (e.g., genetic) influences.","abstract_has_math":false,"creators":["Watts, Tuesday M"],"institution":"University of Essex","degree_name":"phd","degree_level":"doctoral","degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2017,"date_issued":"2017-05","date_published":"2017-05","updated_at":"2026-07-24T02:18:14Z","subjects":["BF Psychology"],"languages":["en"],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":null,"outbound_label":null,"outbound_source":null},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:creator","label":"Author","values":["Watts, Tuesday M"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2017-05"]},{"key":"dc:date.issued","label":"Date","values":["2017-05"]},{"key":"dc:publisher.department","label":"Dc Publisher Department","values":["Department of Psychology"]},{"key":"dc:publisher.institution","label":"Dc Publisher Institution","values":["University of Essex"]},{"key":"dc:relation.isreferencedby","label":"Dc Relation Isreferencedby","values":["https://repository.essex.ac.uk/20189/"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"dc:type.qualificationlevel","label":"Dc Type Qualificationlevel","values":["doctoral"]},{"key":"dc:type.qualificationname","label":"Dc Type Qualificationname","values":["phd"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["BF Psychology"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://repository.essex.ac.uk/20189/1/Final%20Thesis_TW.pdf"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["The present thesis investigated how genetically identical twins with discordant sexual orientations differed in correlates of their sexual orientation in order to understand to what degree non-genetic factors affect the formation of sexual orientation. Because identical twins share 100% of their genes, factors other than genetics may contribute to any differences within these pairs. Chapter 1 gives an overview of the literature. Chapter 2 focuses on childhood gender nonconformity (femininity in males, masculinity in females), which predicts a non-straight (gay, lesbian, or bisexual) sexual orientation in adulthood. In order to avoid the limitations of self-report measures, gender nonconformity of these twins was assessed via observer ratings of their photographs from childhood and adulthood. In addition, although genetically identical twins can differ in their self-reported sexual orientations, it is unclear to what degree these self-assessments reflect observable differences in sexual arousal such as genital response or pupil dilation patterns while viewing sexual stimuli. Chapter 3 focuses on these responses in identical twin pairs with discordant sexual orientations. Finally, differing intrauterine environments during the early development could result in a discordant development of sexual orientation in identical twins. This includes varied prenatal hormonal exposures between twins. Chapter 4 highlights a putative biomarker of early hormonal exposure: the ratio of index to ring finger length (2D:4D), within these twin pairs In combination, findings suggested that these twins differed in many (but not in all) correlates of their sexual orientation, suggesting non-genetic influences. However, there were also subtle similarities within pairs that pointed to potential familial (e.g., genetic) influences."]},{"key":"dc:format","label":"Dc Format","values":["text"]},{"key":"dc:title","label":"Title","values":["The Discordant Development of Sexual Orientation in Identical Twins"]}]}],"canonical_facts":{"dc:creator":["Watts, Tuesday M"],"dc:date":["2017-05"],"dc:date.issued":["2017-05"],"dc:description.abstract":["The present thesis investigated how genetically identical twins with discordant sexual orientations differed in correlates of their sexual orientation in order to understand to what degree non-genetic factors affect the formation of sexual orientation. Because identical twins share 100% of their genes, factors other than genetics may contribute to any differences within these pairs. Chapter 1 gives an overview of the literature. Chapter 2 focuses on childhood gender nonconformity (femininity in males, masculinity in females), which predicts a non-straight (gay, lesbian, or bisexual) sexual orientation in adulthood. In order to avoid the limitations of self-report measures, gender nonconformity of these twins was assessed via observer ratings of their photographs from childhood and adulthood. In addition, although genetically identical twins can differ in their self-reported sexual orientations, it is unclear to what degree these self-assessments reflect observable differences in sexual arousal such as genital response or pupil dilation patterns while viewing sexual stimuli. Chapter 3 focuses on these responses in identical twin pairs with discordant sexual orientations. Finally, differing intrauterine environments during the early development could result in a discordant development of sexual orientation in identical twins. This includes varied prenatal hormonal exposures between twins. Chapter 4 highlights a putative biomarker of early hormonal exposure: the ratio of index to ring finger length (2D:4D), within these twin pairs In combination, findings suggested that these twins differed in many (but not in all) correlates of their sexual orientation, suggesting non-genetic influences. However, there were also subtle similarities within pairs that pointed to potential familial (e.g., genetic) influences."],"dc:format":["text"],"dc:identifier.uri":["https://repository.essex.ac.uk/20189/1/Final%20Thesis_TW.pdf"],"dc:language":["en"],"dc:publisher.department":["Department of Psychology"],"dc:publisher.institution":["University of Essex"],"dc:relation.isreferencedby":["https://repository.essex.ac.uk/20189/"],"dc:subject":["BF Psychology"],"dc:title":["The Discordant Development of Sexual Orientation in Identical Twins"],"dc:type":["Thesis"],"dc:type.qualificationlevel":["doctoral"],"dc:type.qualificationname":["phd"]},"updated_at":"2026-07-24T02:18:14Z"}