Human

== Psychology ==
{{Main|Psychology}}[[File:NIA human brain drawing.jpg|thumb|Drawing of the [[human brain]], showing several important structures]]

The [[human brain]], the focal point of the [[central nervous system]] in humans, controls the [[peripheral nervous system]]. In addition to controlling "lower", involuntary, or primarily [[autonomic nervous system|autonomic]] activities such as [[respiration (physiology)|respiration]] and [[digestion]], it is also the locus of "higher" order functioning such as [[thought]], [[reason]]ing, and [[abstraction]].<ref>{{cite web | url = https://www.pbs.org/wnet/brain/3d/index.html | title = 3-D Brain Anatomy | archive-url = https://web.archive.org/web/20170905064816/https://www.pbs.org/wnet/brain/3d/index.html | archive-date=5 September 2017 | work = The Secret Life of the Brain | publisher = Public Broadcasting Service | access-date = 3 April 2005 }}</ref> These [[mental function|cognitive processes]] constitute the [[mind]], and, along with their [[behavior]]al consequences, are studied in the field of [[psychology]].

Humans have a larger and more developed [[prefrontal cortex]] than other primates, the region of the brain associated with higher [[cognition]].<ref>{{cite journal| vauthors = Stern P |date=22 June 2018|title=The human prefrontal cortex is special|url=https://www.science.org/doi/10.1126/science.2018.360.6395.twil|journal=Science|language=en|volume=360|issue=6395|pages=1311–1312|doi=10.1126/science.360.6395.1311-g|bibcode=2018Sci...360S1311S|s2cid=149581944|issn=0036-8075|doi-access=free}}</ref> This has led humans to proclaim themselves to be more intelligent than any other known species.<ref>{{cite journal| vauthors = Erickson R |date=22 September 2014|title=Are Humans the Most Intelligent Species?|journal=Journal of Intelligence|language=en|volume=2|issue=3|pages=119–121|doi=10.3390/jintelligence2030119|issn=2079-3200|doi-access=free}}</ref> Objectively defining intelligence is difficult, with other animals adapting senses and excelling in areas that humans are unable to.<ref>{{cite web|title=Humans not smarter than animals, just different, experts say|url=https://phys.org/news/2013-12-humans-smarter-animals-experts.html|access-date=24 October 2020|website=phys.org|language=en|archive-date=30 January 2021|archive-url=https://web.archive.org/web/20210130063650/https://phys.org/news/2013-12-humans-smarter-animals-experts.html|url-status=live}}</ref>

There are some traits that, although not strictly unique, do set humans apart from other animals.<ref>{{cite web|vauthors=Robson D|title=We've got human intelligence all wrong|url=https://www.bbc.com/future/article/20161108-weve-got-human-intelligence-all-wrong|access-date=24 October 2020|website=www.bbc.com|language=en|archive-date=31 January 2021|archive-url=https://web.archive.org/web/20210131122837/https://www.bbc.com/future/article/20161108-weve-got-human-intelligence-all-wrong|url-status=live}}</ref> Humans may be the only animals who have [[episodic memory#In animals|episodic memory]] and who can engage in "[[mental time travel#Evolution and human uniqueness|mental time travel]]".<ref>{{cite news|vauthors=Owen J|date=26 February 2015|title=Many Animals{{snd}}Including Your Dog{{snd}}May Have Horrible Short-Term Memories|work=National Geographic News|url=https://www.nationalgeographic.com/animals/article/150225-dogs-memories-animals-chimpanzees-science-mind-psychology|access-date=6 September 2020|archive-date=19 April 2021|archive-url=https://web.archive.org/web/20210419150625/https://www.nationalgeographic.com/animals/article/150225-dogs-memories-animals-chimpanzees-science-mind-psychology|url-status=dead}}</ref> Even compared with other social animals, humans have an unusually high degree of flexibility in their facial expressions.<ref>{{cite journal | vauthors = Schmidt KL, Cohn JF | title = Human facial expressions as adaptations: Evolutionary questions in facial expression research | journal = American Journal of Physical Anthropology | volume = 116 | issue = S33 | pages = 3–24 | date = 2001 | pmid = 11786989 | pmc = 2238342 | doi = 10.1002/ajpa.20001 }}</ref> Humans are the only animals known to cry emotional tears.<ref>{{cite news|vauthors=Moisse K|date=5 January 2011|title=Tears in Her Eyes: A Turnoff for Guys?|language=en|work=ABC News (American)|url=https://abcnews.go.com/Health/MindMoodNews/womens-tears-chemical-turnoff-men/story?id=12540975|access-date=22 April 2020|archive-date=30 January 2021|archive-url=https://web.archive.org/web/20210130050944/https://abcnews.go.com/Health/MindMoodNews/womens-tears-chemical-turnoff-men/story?id=12540975|url-status=live}}</ref> Humans are one of the few animals able to self-recognize in [[mirror test]]s<ref>{{cite news|vauthors=Deleniv S|date=2018|title=The 'me' illusion: How your brain conjures up your sense of self|work=New Scientist|url=https://www.newscientist.com/article/mg23931940-100-the-me-illusion-how-your-brain-conjures-up-your-sense-of-self/|access-date=22 April 2020|archive-date=18 February 2021|archive-url=https://web.archive.org/web/20210218175649/https://www.newscientist.com/article/mg23931940-100-the-me-illusion-how-your-brain-conjures-up-your-sense-of-self/|url-status=live}}</ref> and there is also debate over to what extent humans are the only animals with a [[theory of mind]].<ref>{{cite news|vauthors=Beck J|date=2019|title=Can We Really Know What Animals Are Thinking?|work=Snopes|url=https://www.snopes.com/news/2019/09/07/can-we-really-know-what-animals-are-thinking/|access-date=22 April 2020|archive-date=31 October 2021|archive-url=https://web.archive.org/web/20211031062624/https://www.snopes.com/news/2019/09/07/can-we-really-know-what-animals-are-thinking/|url-status=live}}</ref>

=== Sleep and dreaming ===
{{Main|Sleep|Dream}}
Humans are generally [[Diurnality|diurnal]]. The average sleep requirement is between seven and nine hours per day for an adult and nine to ten hours per day for a child; elderly people usually sleep for six to seven hours. Having less sleep than this is common among humans, even though [[sleep deprivation]] can have negative health effects. A sustained restriction of adult sleep to four hours per day has been shown to correlate with changes in physiology and mental state, including reduced memory, fatigue, aggression, and bodily discomfort.<ref name=Grandner2010>{{cite journal | vauthors = Grandner MA, Patel NP, Gehrman PR, Perlis ML, Pack AI | title = Problems associated with short sleep: bridging the gap between laboratory and epidemiological studies | journal = Sleep Medicine Reviews | volume = 14 | issue = 4 | pages = 239–247 | date = August 2010 | pmid = 19896872 | pmc = 2888649 | doi = 10.1016/j.smrv.2009.08.001 }}</ref><!--cites previous two sentences-->

During sleep humans dream, where they experience sensory images and sounds. Dreaming is stimulated by the [[pons]] and mostly occurs during the [[REM phase of sleep]].<ref>{{cite web| vauthors = Ann L |date=27 January 2005|title=HowStuffWorks "Dreams: Stages of Sleep"|url=https://science.howstuffworks.com/environmental/life/human-biology/dream2.htm|url-status=dead|archive-url=https://web.archive.org/web/20120515212353/https://science.howstuffworks.com/environmental/life/human-biology/dream2.htm|archive-date=15 May 2012|access-date=11 August 2012|publisher=Science.howstuffworks.com}}</ref> The length of a dream can vary, from a few seconds up to 30 minutes.<ref name=Hobson>{{cite journal | vauthors = Hobson JA | title = REM sleep and dreaming: towards a theory of protoconsciousness | journal = Nature Reviews. Neuroscience | volume = 10 | issue = 11 | pages = 803–813 | date = November 2009 | pmid = 19794431 | doi = 10.1038/nrn2716 | s2cid = 205505278 }}</ref> Humans have three to five dreams per night, and some may have up to seven.<ref>{{cite book | vauthors = Empson J | date = 2002 | title = Sleep and dreaming | edition = 3rd | location = New York | publisher = Palgrave/St. Martin's Press }}</ref> Dreamers are more likely to remember the dream if awakened during the REM phase. The events in dreams are generally outside the control of the dreamer, with the exception of [[lucid dream]]ing, where the dreamer is [[self-aware]].<ref>{{cite web| vauthors = Lite J |date=29 July 2010|title=How Can You Control Your Dreams?|url=https://www.scientificamerican.com/article/how-to-control-dreams/|url-status=live|archive-url=https://web.archive.org/web/20150202070145/https://www.scientificamerican.com/article/how-to-control-dreams/|archive-date=2 February 2015|website=Scientific America}}</ref> Dreams can at times make a [[Creativity|creative]] thought occur or give a sense of [[Artistic inspiration|inspiration]].<ref>{{cite book | vauthors = Domhoff W | date = 2002 | title = The scientific study of dreams | publisher = APA Press }}</ref>

=== Consciousness and thought ===
{{Main|Consciousness|Cognition}}
Human consciousness, at its simplest, is [[sentience]] or [[awareness]] of internal or external existence.<ref name="consciousness">{{cite encyclopedia|title=Consciousness|dictionary=Merriam-Webster|access-date=4 June 2012|url=https://www.merriam-webster.com/dictionary/consciousness|archive-date=7 September 2019|archive-url=https://web.archive.org/web/20190907122314/https://www.merriam-webster.com/dictionary/consciousness|url-status=live}}</ref> Despite centuries of analyses, definitions, explanations and debates by philosophers and scientists, consciousness remains puzzling and controversial,<ref name="van_Gulick2004">{{cite encyclopedia|vauthors=van Gulick R|year=2004|title=Consciousness|encyclopedia=Stanford Encyclopedia of Philosophy|url=https://plato.stanford.edu/entries/consciousness/|publisher=Metaphysics Research Lab, Stanford University|access-date=30 July 2022|archive-date=14 October 2019|archive-url=https://web.archive.org/web/20191014065308/https://plato.stanford.edu/entries/consciousness/|url-status=live}}</ref> being "at once the most familiar and most mysterious aspect of our lives".<ref>{{cite book| vauthors = Schneider S, Velmans M |author2-link=Max Velmans |title=The Blackwell Companion to Consciousness |publisher=Wiley|year=2008|isbn=978-0-470-75145-9| veditors = Velmans M, Schneider S |chapter=Introduction}}</ref> The only widely agreed notion about the topic is the intuition that it exists.<ref>{{cite book| vauthors = Searle J |title=The Oxford companion to philosophy|publisher=Oxford University Press|year=2005|isbn=978-0-19-926479-7| veditors = Honderich T|chapter=Consciousness|author-link=John Searle}}</ref> Opinions differ about what exactly needs to be studied and explained as consciousness. Some philosophers divide consciousness into phenomenal consciousness, which is sensory experience itself, and access consciousness, which can be used for reasoning or directly controlling actions.<ref name="Bl">{{cite journal | vauthors = Block N | title = On a confusion about a function of consciousness. | journal = Behavioral and Brain Sciences | date = June 1995 | volume = 18 | issue = 2 | pages = 227–247 | doi = 10.1017/S0140525X00038474 | s2cid = 246244859 | doi-access = free }}</ref> It is sometimes synonymous with 'the mind', and at other times, an aspect of it. Historically it is associated with [[introspection]], private [[thought]], [[imagination]] and [[Volition (psychology)|volition]].<ref name="JJ3">{{cite book|vauthors=Jaynes J|url=https://s-f-walker.org.uk/pubsebooks/pdfs/Julian_Jaynes_The_Origin_of_Consciousness.pdf|title=The Origin of Consciousness in the Breakdown of the Bicameral Mind|publisher=Houghton Mifflin|year=2000|isbn=0-618-05707-2|author-link=Julian Jaynes|orig-year=1976|access-date=25 October 2020|archive-date=7 August 2019|archive-url=https://web.archive.org/web/20190807100304/https://s-f-walker.org.uk/pubsebooks/pdfs/Julian_Jaynes_The_Origin_of_Consciousness.pdf|url-status=dead}}</ref> It now often includes some kind of [[experience]], [[cognition]], [[feeling]] or [[perception]]. It may be 'awareness', or '[[Meta-cognition|awareness of awareness]]', or [[self-awareness]].<ref name="Rochat 2003 717–731">{{cite journal | vauthors = Rochat P | title = Five levels of self-awareness as they unfold early in life | journal = Consciousness and Cognition | volume = 12 | issue = 4 | pages = 717–731 | date = December 2003 | pmid = 14656513 | doi = 10.1016/s1053-8100(03)00081-3 | s2cid = 10241157 }}</ref> There might be different levels or [[Higher-order theories of consciousness|orders of consciousness]],<ref name="Carruthers2011">{{cite web|vauthors=Carruthers P|date=15 August 2011|title=Higher-Order Theories of Consciousness|url=https://plato.stanford.edu/entries/consciousness-higher/|access-date=31 August 2014|website=Stanford Encyclopedia of Philosophy|archive-date=13 April 2021|archive-url=https://web.archive.org/web/20210413163246/https://plato.stanford.edu/entries/consciousness-higher/|url-status=live}}</ref> or different kinds of consciousness, or just one kind with different features.<ref name="Antony2001">{{cite journal| vauthors = Antony MV |year=2001|title=Is ''consciousness'' ambiguous?|journal=Journal of Consciousness Studies|volume=8|pages=19–44}}</ref>

The process of acquiring knowledge and understanding through thought, experience, and the senses is known as cognition.<ref>{{cite web|title=Cognition|url=https://www.lexico.com/definition/cognition|access-date=6 May 2020|website=Lexico|publisher=[[Oxford University Press]] and [[Dictionary.com]]|archive-date=8 July 2016|archive-url=https://web.archive.org/web/20160708041349/http://www.oxforddictionaries.com/definition/english/cognition|url-status=dead}}</ref> The human brain [[perception|perceives]] the external world through the [[sense]]s, and each individual human is influenced greatly by his or her experiences, leading to [[subjectivity|subjective]] views of [[existence]] and the passage of time.<ref>{{cite book | vauthors = Glattfelder JB | title = Information—Consciousness—Reality| chapter = The Consciousness of Reality|date=2019 |pages=515–595| veditors = Glattfelder JB |series=The Frontiers Collection|place=Cham|publisher=Springer International Publishing|language=en|doi=10.1007/978-3-030-03633-1_14|isbn=978-3-030-03633-1 | s2cid = 189379814}}</ref> The nature of thought is central to psychology and related fields. [[Cognitive psychology]] studies [[cognition]], the [[mental function|mental processes]] underlying behavior.<ref>{{cite web|title=American Psychological Association (2013). Glossary of psychological terms|url=https://www.apa.org/research/action/glossary.aspx|access-date=13 August 2014|publisher=Apa.org|archive-date=8 July 2014|archive-url=https://web.archive.org/web/20140708064652/http://www.apa.org/research/action/glossary.aspx|url-status=live}}</ref> Largely focusing on the development of the human mind through the life span, [[developmental psychology]] seeks to understand how people come to perceive, understand, and act within the world and how these processes change as they age.<ref>{{cite web|title=Developmental Psychology Studies Human Development Across the Lifespan|url=https://www.apa.org/action/science/developmental/index.aspx|url-status=dead|archive-url=https://web.archive.org/web/20140709054242/https://www.apa.org/action/science/developmental/index.aspx|archive-date=9 July 2014|access-date=28 August 2017|website=www.apa.org|language=en}}</ref><ref>{{cite book| vauthors = Burman E |title=Deconstructing Developmental Psychology|publisher=Routledge|year=2017|isbn=978-1-138-84695-1|location=New York }}</ref> This may focus on intellectual, cognitive, neural, social, or [[moral development]]. [[Psychologists]] have developed intelligence tests and the concept of [[intelligence quotient]] in order to assess the relative intelligence of human beings and study its [[Distribution (mathematics)|distribution]] among population.<ref>{{Cite journal| vauthors = Colom R |date=1 January 2004|title=Intelligence Assessment |journal=Encyclopedia of Applied Psychology|language=en|pages=307–314|doi=10.1016/B0-12-657410-3/00510-9|isbn=978-0-12-657410-4}}</ref>

=== Motivation and emotion ===
{{Main|Motivation|Emotion}}
[[File:Plate depicting emotions of grief from Charles Darwin's book The Expression of the Emotions.jpg|right|thumb|Illustration of grief from [[Charles Darwin]]'s 1872 book ''[[The Expression of the Emotions in Man and Animals]]'']]

Human motivation is not yet wholly understood. From a psychological perspective, [[Maslow's hierarchy of needs]] is a well-established theory that can be defined as the process of satisfying certain needs in ascending order of complexity.<ref>{{cite web|url=https://www.simplypsychology.org/maslow.html|title=Maslow's Hierarchy of Needs|vauthors=McLeod S|date=20 March 2020|website=Simplypsychology.org|publisher=Simply Scholar Limited|access-date=4 April 2020|quote=Maslow's hierarchy of needs is a motivational theory in psychology comprising a five-tier model of human needs, often depicted as hierarchical levels within a pyramid. Needs lower down in the hierarchy must be satisfied before individuals can attend to needs higher up.|archive-date=8 November 2018|archive-url=https://web.archive.org/web/20181108083314/https://www.simplypsychology.org/maslow.html|url-status=live}}</ref> From a more general, philosophical perspective, human motivation can be defined as a commitment to, or withdrawal from, various goals requiring the application of human ability. Furthermore, [[incentive]] and [[preference]] are both factors, as are any perceived links between incentives and preferences. [[Volition (psychology)|Volition]] may also be involved, in which case willpower is also a factor. Ideally, both motivation and volition ensure the selection, striving for, and [[Realisation (metrology)|realization]] of goals in an optimal manner, a [[Function (biology)|function]] beginning in childhood and continuing throughout a lifetime in a process known as [[socialization]].<ref>{{cite book| vauthors = Heckhausen J, Heckhausen H |chapter=Motivation and Action: Introduction and Overview |date=28 March 2018|title=Motivation and Action|location=Introduction and Overview|publisher=Springer, Cham|page=1|isbn=978-3-319-65093-7|doi=10.1007/978-3-319-65094-4_1}}</ref>

Emotions are [[biological]] states associated with the nervous system<ref>{{cite journal | vauthors = Damasio AR | title = Emotion in the perspective of an integrated nervous system | journal = Brain Research. Brain Research Reviews | volume = 26 | issue = 2–3 | pages = 83–86 | date = May 1998 | pmid = 9651488 | doi = 10.1016/s0165-0173(97)00064-7 | s2cid = 8504450 }}</ref><ref>{{cite book| vauthors = Ekman P, Davidson RJ |title=The Nature of emotion : fundamental questions|date=1994|publisher=Oxford University Press|isbn=978-0-19-508944-8|location=New York|pages=291–293|quote=Emotional processing, but not emotions, can occur unconsciously.}}</ref> brought on by [[Neurophysiology|neurophysiological]] changes variously associated with thoughts, feelings, behavioral responses, and a degree of [[pleasure]] or [[Suffering|displeasure]].<ref>{{cite journal | vauthors = Cabanac M | date = 2002 | title = What is emotion? | journal = Behavioural Processes | volume = 60 | issue = 2 | pages = 69–83 | quote = Emotion is any mental experience with high intensity and high hedonic content (pleasure/displeasure) | doi = 10.1016/S0376-6357(02)00078-5 | pmid = 12426062 | s2cid = 24365776 }}</ref><ref name="Schacter">{{cite book| vauthors = Scirst DL |url= https://archive.org/details/psychology0000scha/page/310 |title=Psychology Second Edition|publisher=Worth Publishers|year=2011|isbn=978-1-4292-3719-2|location=New York|page=[https://archive.org/details/psychology0000scha/page/310 310]}}</ref> They are often [[Reciprocal influence|intertwined]] with [[Mood (psychology)|mood]], [[temperament]], [[Personality psychology|personality]], [[disposition]], [[creativity]],<ref>{{cite journal | vauthors = Averill JR | title = Individual differences in emotional creativity: structure and correlates | journal = Journal of Personality | volume = 67 | issue = 2 | pages = 331–371 | date = April 1999 | pmid = 10202807 | doi = 10.1111/1467-6494.00058 }}</ref> and motivation. Emotion has a significant influence on human behavior and their ability to learn.<ref>{{cite journal | vauthors = Tyng CM, Amin HU, Saad MN, Malik AS | title = The Influences of Emotion on Learning and Memory | journal = Frontiers in Psychology | volume = 8 | page = 1454 | date = 2017 | pmid = 28883804 | pmc = 5573739 | doi = 10.3389/fpsyg.2017.01454 | doi-access = free }}</ref> Acting on extreme or uncontrolled emotions can lead to social disorder and crime,<ref>{{cite book|vauthors=Van Gelder JL|url=https://www.researchgate.net/publication/317042659|title=Oxford Bibliographies in Criminology|publisher=Oxford University Press|date=November 2016|veditors=Wright R|chapter=Emotions in Criminal Decision Making|access-date=30 July 2022|archive-date=29 January 2021|archive-url=https://web.archive.org/web/20210129211201/https://www.researchgate.net/publication/317042659|url-status=live}}</ref> with studies showing criminals may have a lower [[emotional intelligence]] than normal.<ref>{{cite journal | vauthors = Sharma N, Prakash O, Sengar KS, Chaudhury S, Singh AR | title = The relation between emotional intelligence and criminal behavior: A study among convicted criminals | journal = Industrial Psychiatry Journal | volume = 24 | issue = 1 | pages = 54–58 | date = 2015 | pmid = 26257484 | pmc = 4525433 | doi = 10.4103/0972-6748.160934 | doi-access = free }}</ref>

Emotional experiences perceived as [[pleasure|pleasant]], such as [[joy]], [[Interest (emotion)|interest]] or [[contentment]], contrast with those perceived as [[suffering|unpleasant]], like [[anxiety]], [[sadness]], [[anger]], and [[Depression (mood)|despair]].<ref>{{cite journal | vauthors = Fredrickson BL | title = The role of positive emotions in positive psychology. The broaden-and-build theory of positive emotions | journal = The American Psychologist | volume = 56 | issue = 3 | pages = 218–226 | date = March 2001 | pmid = 11315248 | pmc = 3122271 | doi = 10.1037/0003-066X.56.3.218 }}</ref> [[Happiness]], or the state of being happy, is a human emotional condition. The definition of happiness is a common philosophical topic. Some define it as experiencing the [[feeling]] of positive [[Affect (psychology)|emotional affects]], while avoiding the negative ones.<ref>{{cite journal | vauthors = Haybron DM | title = The proper pursuit of happiness. | journal = Res Philosophica | date = August 2013 | volume = 90 | issue = 3 | pages = 387–411 | doi = 10.11612/resphil.2013.90.3.5 }}</ref><ref>{{cite web | vauthors = Haybron DM | date = 13 April 2014 | work = The Opinion Pages | publisher = The New York Times | title = Happiness and Its Discontents | url = https://opinionator.blogs.nytimes.com/2014/04/13/happiness-and-its-discontents/ | quote = I would suggest that when we talk about happiness, we are actually referring, much of the time, to a complex emotional phenomenon. Call it emotional well-being. Happiness as emotional well-being concerns your emotions and moods, more broadly your emotional condition as a whole. To be happy is to inhabit a favorable emotional state.... On this view, we can think of happiness, loosely, as the opposite of anxiety and depression. Being in good spirits, quick to laugh and slow to anger, at peace and untroubled, confident and comfortable in your own skin, engaged, energetic and full of life. | access-date = 30 July 2022 | archive-date = 12 October 2018 | archive-url = https://web.archive.org/web/20181012094415/https://opinionator.blogs.nytimes.com/2014/04/13/happiness-and-its-discontents/ | url-status = live }}</ref> Others see it as an appraisal of [[life satisfaction]] or [[quality of life]].<ref>{{cite book| vauthors = Graham MC |title=Facts of Life: ten issues of contentment|date=2014|publisher=Outskirts Press|isbn=978-1-4787-2259-5|pages=6–10}}</ref> Recent research suggests that being happy might involve experiencing some negative emotions when humans feel they are warranted.<ref>{{cite web|date=14 August 2017|title=Secret to happiness may include more unpleasant emotions: Research contradicts idea that people should always seek pleasure to be happy|url=https://www.sciencedaily.com/releases/2017/08/170814092813.htm|access-date=25 October 2020|website=ScienceDaily|publisher=[[American Psychological Association]]|language=en|archive-date=11 November 2020|archive-url=https://web.archive.org/web/20201111181025/https://www.sciencedaily.com/releases/2017/08/170814092813.htm|url-status=live}}</ref>

=== Sexuality and love ===
{{Main|Human sexuality|Love}}
[[File:Sweet Baby Kisses Family Love.jpg|thumb|Human parents often display [[familial love]] for their children.]]
For humans, sexuality involves [[biological]], [[erotic]], [[Physical intimacy|physical]], [[Emotional intimacy|emotional]], [[social]], or [[Spirituality|spiritual]] feelings and behaviors.<ref name="S. Greenberg">{{cite book|vauthors=Greenberg JS, Bruess CE, Oswalt SB|url={{GBurl|id=8iarCwAAQBAJ|p=4}}|title=Exploring the Dimensions of Human Sexuality|publisher=[[Jones & Bartlett Publishers]]|year=2016|isbn=978-1-284-08154-1|pages=4–10|quote=Human sexuality is a part of your total personality. It involves the interrelationship of biological, psychological, and sociocultural dimensions. [...] It is the total of our physical, emotional, and spiritual responses, thoughts, and feelings.|access-date=21 June 2017}}</ref><ref name="Bolin">{{cite book| vauthors = Bolin A, Whelehan P |url={{GBurl|id=qrPHYok19v8C|p=32}}|title=Human Sexuality: Biological, Psychological, and Cultural Perspectives|publisher=[[Taylor & Francis]]|year=2009|isbn=978-0-7890-2671-2|pages=32–42}}</ref> Because it is a broad term, which has varied with historical contexts over time, it lacks a precise definition.<ref name="Bolin" /> The biological and physical aspects of sexuality largely concern the [[Human reproduction|human reproductive functions]], including the [[human sexual response cycle]].<ref name="S. Greenberg" /><ref name="Bolin" /> Sexuality also affects and is affected by cultural, political, legal, philosophical, [[Morality|moral]], [[ethical]], and religious aspects of life.<ref name="S. Greenberg" /><ref name="Bolin" /> Sexual desire, or ''[[libido]]'', is a basic mental state present at the beginning of sexual behavior. Studies show that men desire sex more than women and [[Masturbation|masturbate]] more often.<ref>{{cite journal| vauthors = Younis I, Abdel-Rahman SH |date=2013|title=Sex difference in libido |journal=Human Andrology|language=en-US|volume=3|issue=4|pages=85–89|doi=10.1097/01.XHA.0000432482.01760.b0|s2cid=147235090}}</ref>

Humans can fall anywhere along a continuous scale of [[sexual orientation]],<ref name="APASO">{{cite web|title=Sexual orientation, homosexuality and bisexuality|url=https://www.apa.org/helpcenter/sexual-orientation.aspx|archive-url=https://web.archive.org/web/20130808032050/https://www.apa.org/helpcenter/sexual-orientation.aspx|archive-date=8 August 2013|access-date=10 August 2013|publisher=[[American Psychological Association]]}}</ref> although most humans are [[heterosexual]].<ref name=Bailey16 /><ref name=LeVay /> While [[homosexuality|homosexual]] behavior [[Homosexual behavior in animals|occurs in some other animals]], only humans and [[Sheep|domestic sheep]] have so far been found to exhibit exclusive preference for same-sex relationships.<ref name=Bailey16 /> Most evidence supports nonsocial, [[biology and sexual orientation|biological causes of sexual orientation]],<ref name="Bailey16">{{cite journal | vauthors = Bailey JM, Vasey PL, Diamond LM, Breedlove SM, Vilain E, Epprecht M | title = Sexual Orientation, Controversy, and Science | journal = Psychological Science in the Public Interest | volume = 17 | issue = 2 | pages = 45–101 | date = September 2016 | pmid = 27113562 | doi = 10.1177/1529100616637616 | doi-access = free }}</ref> as cultures that are very tolerant of homosexuality do not have significantly higher rates of it.<ref name="LeVay">{{cite book|vauthors=LeVay S|url={{GBurl|id=HmQFFfa03nkC}}|title=Gay, Straight, and the Reason Why: The Science of Sexual Orientation|date=2017|publisher=Oxford University Press|isbn=978-0-19-975296-6|pages=8, 19|access-date=30 July 2022}}</ref><ref name="Balthazart">{{cite book|vauthors=Balthazart J|url={{GBurl|id=3fjGjlcVINkC}}|title=The Biology of Homosexuality|date=2012|publisher=Oxford University Press|isbn=978-0-19-983882-0|pages=13–14|access-date=30 July 2022}}</ref> Research in [[neuroscience]] and [[genetics]] suggests that other aspects of human sexuality are biologically influenced as well.<ref name=Buss2003>{{cite book | vauthors = Buss DM |year=2003 |title=The Evolution of Desire: Strategies of Human Mating. | edition = Revised |location=New York |publisher=Basic Books |isbn=978-0-465-00802-5 |url=https://archive.org/details/evolutionofdesir00buss }}</ref>

Love most commonly refers to a feeling of strong attraction or emotional [[Attachment (psychology)|attachment]]. It can be impersonal (the love of an object, ideal, or strong political or spiritual connection) or interpersonal (love between humans).<ref name="Fromm, Erich 2000">{{cite book | vauthors = Fromm E |title=The art of loving |date=2000 |publisher= Harper Perennial |location=New York |isbn=978-0-06-095828-2}}</ref> When in love [[dopamine]], [[norepinephrine]], [[serotonin]] and other chemicals stimulate the brain's [[pleasure center]], leading to side effects such as increased [[heart rate]], loss of [[Anorexia (symptom)|appetite]] and [[Insomnia|sleep]], and an [[Euphoria|intense feeling of excitement]].<ref>{{cite web|date=14 February 2017|title=Love, Actually: The science behind lust, attraction, and companionship|url=https://sitn.hms.harvard.edu/flash/2017/love-actually-science-behind-lust-attraction-companionship/|access-date=25 October 2020|website=Science in the News|language=en-US|archive-date=28 October 2020|archive-url=https://web.archive.org/web/20201028090542/http://sitn.hms.harvard.edu/flash/2017/love-actually-science-behind-lust-attraction-companionship/|url-status=live}}</ref>