Differential psychology

'''Differential psychology''' studies the ways in which individuals differ in their behavior and the processes that underlie it. It is a discipline that develops classifications (taxonomies) of psychological individual differences. This is distinguished from other aspects of psychology <ref>{{cite web | url=https://www.psicologiasemfronteiras.com.br/2019/07/o-que-e-psicologia.html | title=Psicologa sp }}</ref><ref>{{cite news |title=Brief therapy |url=https://therapie-aix.fr/}}</ref> in that, although psychology is ostensibly a study of individuals, modern psychologists often study groups, or attempt to discover general psychological processes that apply to all individuals.<ref name="Ergodicity">{{cite journal |author1=Fisher, A.J.| display-authors=etal| year = 2018 | title = Lack of group-to-individual generalizability is a threat to human subjects research| journal = PNAS | volume = 115 | issue = 27 | pages = 6106–6115| doi=10.1073/pnas.1711978115| pmid=29915059| pmc=6142277| bibcode=2018PNAS..115E6106F| doi-access=free}}</ref> This particular area of psychology was first named and still retains the name of "differential psychology" by William Stern in his 1900 book "''Über Psychologie der individuellen Differenzen''" (On the Psychology of Individual Differences).<ref>{{Cite journal |last1=Kovacs |first1=Kristof |last2=Pléh |first2=Csaba |date=2023-02-21 |title=William Stern: The Relevance of His Program of 'Differential Psychology' for Contemporary Intelligence Measurement and Research |journal=Journal of Intelligence |volume=11 |issue=3 |pages=41 |doi=10.3390/jintelligence11030041 |doi-access=free |issn=2079-3200 |pmc=10054024 |pmid=36976134}}</ref>

While prominent psychologists, including Stern, have been widely credited for the concept of differential psychology, historical records show that it was Charles Darwin (1859) who first spurred the scientific interest in the study of individual differences. The interest was further pursued by half-cousin Francis Galton in his attempt to quantify individual differences among people.<ref>Cohen, R., Swerdlik, M. and Sturman, E., 2013. Psychological Testing And Assessment. 7th ed. New York, NY: McGraw-Hill.</ref>

For example, in evaluating the effectiveness of a new therapy, the mean performance of the therapy in one treatment group might be compared to the mean effectiveness of a placebo (or a well-known therapy) in a second, control group. In this context, differences between individuals in their reaction to the experimental and control manipulations are actually treated as errors rather than as interesting phenomena to study. This approach is applied because psychological research depends upon statistical controls that are only defined upon groups of people.

== Importance of individual differences == Importantly, individuals can also differ not only in their current state, but in the magnitude or even direction of response to a given stimulus.<ref>{{Cite journal |last1=Larsen |first1=Randy J. |last2=Diener |first2=Ed |date=1987-03-01 |title=Affect intensity as an individual difference characteristic: A review |url=https://dx.doi.org/10.1016/0092-6566%2887%2990023-7 |journal=Journal of Research in Personality |language=en |volume=21 |issue=1 |pages=1–39 |doi=10.1016/0092-6566(87)90023-7 |issn=0092-6566|url-access=subscription }}</ref> Such phenomena, often explained in terms of inverted-U response curves, place differential psychology at an important location in such endeavours as personalized medicine, in which diagnoses are customised for an individual's response profile.{{Cn|date=September 2022}}

== Areas of study == Individual differences research typically includes personality, temperament (neuro-chemically based behavioural traits), motivation, intelligence, ability, IQ, interests, values, self-concept, self-efficacy, and self-esteem.<ref>{{cite journal |author1=Chamorro-Premuzic, T. |author2=Furnham, A. |name-list-style=amp |year=2006 |title=Intellectual competence and the intelligent personality: A third way in differential psychology |url=http://www.goldsmiths.ac.uk/psychology/downloads/ChamorroPremuzicFurnham2006RGP.pdf |url-status=unfit |journal=Review of General Psychology |volume=10 |issue=3 |pages=251–267 |doi=10.1037/1089-2680.10.3.251 |s2cid=146278640 |archive-url=https://web.archive.org/web/20090319201449/http://www.goldsmiths.ac.uk/psychology/downloads/ChamorroPremuzicFurnham2006RGP.pdf |archive-date=March 19, 2009}}</ref> Although the United States has seen a decrease in individual differences research since the 1960s, researchers are found in a variety of applied and experimental fields.<ref>{{Citation |last1=Revelle |first1=William |title=Individual Differences and Differential Psychology |date=2013-03-12 |url=http://dx.doi.org/10.1002/9781444343120.ch1 |work=The Wiley-Blackwell Handbook of Individual Differences |pages=1–38 |place=Oxford, UK |publisher=Wiley-Blackwell |access-date=2023-02-15 |last2=Wilt |first2=Joshua |last3=Condon |first3=David M.|doi=10.1002/9781444343120.ch1 |isbn=9781444334388 |url-access=subscription }}</ref> These fields include clinical psychology, psychophysiology, educational psychology, Industrial and organizational psychology, personality psychology, social psychology, behavioral genetics, and developmental psychology programs, in the neo-Piagetian theories of cognitive development in particular.

== Methods of research == To study individual differences, psychologists use a variety of methods. The method is to compare and analyze the psychology and behaviour of individuals or groups under different environmental conditions. By correlating observed psychological and behavioral differences with known accompanying environments, the relative roles of different variables in psychological and behavioral development can be probed. Psychophysiological experiments on both humans and other mammals include EEG and ERPs,<ref>{{Cite journal |last=Clayson |first=Peter E. |date=2024 |title=The psychometric upgrade psychophysiology needs |journal=Psychophysiology |language=en |volume=61 |issue=3 |article-number=e14522 |doi=10.1111/psyp.14522 |pmid=38228400 |issn=0048-5772|pmc=10922751 }}</ref> PET-scans, MRI, functional MRI, neurochemistry<ref>{{cite book|last1 = Brady| first1 = ST |author2=Siegel GJ, Albers RW, Price DL.| year = 2012|title = Basic Neurochemistry. McGill Press}}</ref><ref>{{cite book|last1 = Kandel| first1 = ER|author2=Schwartz JH, Jessell TM.| year = 2000|title = Principles of Neural Science, fourth edition. McGraw-Hill Companies.}}</ref> experiments with neurotransmitter and hormonal systems, caffeine and controlled drug challenges. These methods can be used for a search of biomarkers of consistent, biologically based behavioural patterns (temperament traits and symptoms of psychiatric disorders). Other sets of methods include behavioural experiments, to see how different people behave in similar settings. Behavioural experiments are often used in personality and social psychology, and include lexical and self-report methods where people are asked to complete paper-based and computer-based forms prepared by psychologists.

==See also== {{Library resources box|by=no|onlinebooks=no|about=yes|wikititle=differential psychology}} * Temperament * Intelligence * Behavioral genetics * Personality psychology * Educational psychology

==References== ===Footnotes=== {{Reflist}} ===Sources=== * {{cite journal|doi=10.1080/00291463.1958.10780375|title=Historical Note on the Term Differential Psychology|year=1958|last1=Jarl|first1=Vidkunn Coucheron|journal=Nordisk Psykologi|volume=10|issue=2|pages=114–116}} * {{cite journal|author=Richters, J. E. |title=Incredible utility: The lost causes and causal debris of psychological science |journal=Basic and Applied Social Psychology |date=2021 |volume=43 |issue=6 |pages=366–405 |doi=10.1080/01973533.2021.1979003 |s2cid=236565514 |url=https://doi.org/10.1080/01973533.2021.1979003|url-access=subscription }} * [http://www.wilderdom.com/personality/L1-1Introduction.html Introduction to Individual Differences] (Wilderdom) * {{cite book|author1=Maltby, J.|author2=Day, L.|author3=Macaskill, A.|name-list-style=amp|year=2007|title=Personality, Individual Differences and Intelligence|location=London|publisher=Pearson Education|url=http://www.pearsoned.co.uk/Bookshop/detail.asp?item=100000000090816}} * {{cite journal|author1=Buss, D.M.|author2=Greiling, H.|name-list-style=amp|year=1999|url=http://labs.la.utexas.edu/buss/files/2015/09/adapt-ID-revisited-1999-jop.pdf|title=Adaptive Individual Differences|journal=Journal of Personality|volume=67|issue=2|pages=209–243|doi=10.1111/1467-6494.00053|citeseerx=10.1.1.387.3246}} * {{cite journal|author1=Kanai, R.|author2=Rees, G.|name-list-style=amp|year=2011|title=The structural basis of inter-individual differences in human behaviour and cognition|journal=Nature Reviews Neuroscience|volume=12|issue=4|pages=231–241|doi=10.1038/nrn3000|pmid=21407245|s2cid=7103414 |url=https://figshare.com/articles/journal_contribution/23391917 }} *{{cite book|author=Tyler, L.E.|year=1965|title=The psychology of human differences|url=https://archive.org/details/psychologyofhuma00tyle|url-access=registration|location=New York|publisher=Appleton Century Crofts}} *{{usurped|1=[https://web.archive.org/web/20121018221515/http://www.intelltheory.com/ Timeline of researchers and brief biographies]}}

Category:Behavioural sciences Category:Differential psychology