Gijsbert Stoet

Introduction

Gijsbert Stoet is a Dutch-born experimental psychologist and Professor of Psychology at the University of Essex. He works on two problems that rarely sit together in one career: the fine-grained architecture of attention and executive control, measured in milliseconds, and the cross-national statistics of sex differences in educational achievement, measured in decades. He is also the author of PsyToolkit, an open web platform that lets researchers build and run reaction-time experiments and questionnaires without writing server code, and it is through that tool that he is probably known to more working psychologists than through any of his papers.

Stoet's name entered public debate in 2018 with the gender-equality paradox: the finding, reported with David Geary, that countries with higher measured gender equality tend to show larger rather than smaller sex differences in who takes science, technology, engineering and mathematics (STEM) degrees. The result was covered by outlets including The New York Times, the BBC and Die Zeit, and it has been disputed ever since.

Early Life and Education

Stoet was born in the Netherlands and read psychology at the University of Groningen, where he completed his master's degree in 1993. He moved to Germany for doctoral work at the University of Munich (LMU), receiving his PhD summa cum laude in 1998. His training there combined psychology with philosophy and linguistics, an unusual combination that shows up later in the way he writes about concepts such as "attention" and "sex difference" — he tends to ask what a term is doing before he asks what causes it.

His doctoral research was in experimental cognitive psychology, and the methods he learned there — precise stimulus timing, tightly controlled trial structures, careful handling of outliers — became the substrate of both his later empirical work and the software he would write to run it.

Academic and Professional Career

After Munich, Stoet held research and teaching posts across Europe and the United States. His early postdoctoral work was at the Max Planck Institute for Psychological Research in Munich, followed by a period at the Washington University School of Medicine in St. Louis, where he worked at the interface of cognitive psychology and neuroimaging. He then spent a decade in the United Kingdom: at the University of Glasgow, at Leeds Beckett University, at the University of the West of England, and finally at the University of Leeds, where he was a reader and then professor before moving to take up a chair at the University of Essex in 2018.

The Essex appointment consolidated a portfolio that had by then split into two visibly separate halves. One is laboratory and online experimentation on attention and cognitive control. The other — conducted largely with long-standing collaborator David C. Geary of the University of Missouri — is the analysis of large international assessment datasets such as PISA and TIMSS. Stoet has never treated the two as a single programme, and he has written that he came to the educational data partly because the cognitive findings about individual differences seemed to have no clear bridge to population-level outcomes.

Alongside these, he has maintained PsyToolkit continuously since 2005, an unpaid piece of research infrastructure that now underpins thousands of studies and is credited in hundreds of published papers.

Major Contributions to Psychology

Attention and executive control

Stoet's experimental work addresses how the cognitive system selects one task when another is waiting. He has published on the psychological refractory period, on task switching, and on the conditions under which a secondary task intrudes on a primary one. A recurring theme is that "control" is not a single faculty but a set of context-dependent operations that can look like a capacity limit in one design and like a strategic setting in another.

Sex differences in multitasking

In 2013 Stoet and colleagues reported what became one of the most widely reported psychology findings of the decade. In a study published in BMC Psychology, men and women performed a task-switching battery, and the female advantage that emerged was explained almost entirely by a small number of fast-switching individuals rather than by a general sex difference in the population. The nuance was largely lost in press coverage. Stoet has since used the episode as an example of how a null-ish, heavily qualified result becomes a headline claim.

The gender-equality paradox

The 2018 paper with Geary in Psychological Science analysed PISA data from several dozen countries and reported that as national gender-equality indices rose, the female advantage in reading grew while girls' relative inclination toward STEM fields fell. The two effects reinforced one another: in more gender-equal countries, the girls most capable of STEM study were also the girls most able to pursue other things. The authors proposed that where economic and social constraints are relaxed, freely expressed preferences diverge more, not less.

That proposal has proved far more contested than the descriptive finding.

PsyToolkit and the teaching of method

PsyToolkit provides a browser-based environment for programming experiments, a server for hosting them, and a questionnaire module with validated instruments. Its significance is practical rather than theoretical: it lowered the cost of running reaction-time research to near zero at exactly the moment when online data collection became normal, and it made reproducible stimulus code a routine expectation rather than a favour.

The original 2010 paper described a Linux package for programming experiments; the 2017 paper in Teaching of Psychology deliberately repositioned the platform for the classroom, where students can design, run and analyse their own study within a single term. Stoet extended the same logic into a textbook, Introduction to Psychology as a Science (SAGE, 2019), built entirely around hands-on exercises run in PsyToolkit. The through-line is an argument about training: psychology students who only ever read about experiments, he has suggested, come to believe that method is somebody else's job.

Sex differences in educational achievement

The second half of Stoet's output is quantitative social science rather than experimentation. Working with David C. Geary, he exploited the fact that international assessments such as PISA and TIMSS now provide decades of comparable data across dozens of countries, which makes it possible to ask whether a sex difference that looks biological within one nation behaves like a constant across nations. Their 2013 PLoS ONE paper reported that the female advantage in reading and the male advantage in mathematics are inversely related across countries — a result that is difficult to reconcile with any purely biological account and that set up the paradox paper five years later.

Major Publications

• Stoet, G. (2010). PsyToolkit: A software package for programming psychological experiments using Linux. Behavior Research Methods, 42(4), 1096–1104.
• Stoet, G. (2017). PsyToolkit: A novel web-based method for running online questionnaires and reaction-time experiments. Teaching of Psychology, 44(1), 24–31.
• Stoet, G., O'Connor, D. B., Conner, M., & Laws, K. R. (2013). Are women better than men at multi-tasking? BMC Psychology, 1, 18.
• Stoet, G., & Geary, D. C. (2013). Sex differences in mathematics and reading achievement are inversely related: Within- and across-nation assessment of 10 years of PISA data. PLoS ONE, 8(3), e57988.
• Stoet, G., & Geary, D. C. (2018). The gender-equality paradox in science, technology, engineering, and mathematics education. Psychological Science, 29(4), 581–593.
• Stoet, G. (2019). Introduction to Psychology as a Science: A hands-on approach using PsyToolkit. SAGE.

An up-to-date list of his papers is maintained on his own academic CV, and his profiles on Google Scholar and ResearchGate carry downloadable versions of most recent work.

Impact and Legacy

Stoet's durable contribution is likely to be infrastructural. PsyToolkit changed what a graduate student or a lecturer at a teaching-focused institution can do without a grant, and it arrived before the commercial online-experiment market matured.

His substantive work is more contested. The gender-equality paradox is a genuinely uncomfortable result for anyone who assumes that removing barriers mechanically reduces group differences, and Stoet and Geary deserve credit for stating it plainly. But the criticisms are substantial. First, the design is cross-national and correlational: it relates a country-level index to a country-level difference, and nothing in it licenses inferences about individuals. Second, the finding is sensitive to the choice of index — the World Economic Forum's Global Gender Gap Index is the measure most often used, and it is not a neutral or uncontested proxy for equality. Third, and most damaging, Thomas Breda and colleagues showed in a 2020 PNAS paper that a measure of gender-essentialist beliefs explains the same pattern at least as well as equality indices do, which reframes the paradox as evidence about stereotypes rather than about freedom of choice. Stoet and Geary's response is that the two explanations need not compete, and that no single study of this kind can settle a question about causal pathways.

The dispute is still open, and part of the reason is that the two sides are measuring different things. "Gender equality" in these analyses is a composite of economic participation, educational attainment, health and political empowerment — a basket in which some components plausibly push in opposite directions. Gender-essentialist belief is a psychological variable measured at the individual level. Neither study establishes what happens to a particular girl choosing a particular degree, which is the question policy actually cares about.

The multitasking episode carries a related lesson. Stoet's own paper was careful — the sex difference it reported was small and was concentrated in a minority of participants — and the global coverage was not; the retraction of nuance happened without his being able to prevent it. His occasional writing for general audiences, including a Psychology Today column, is in part an attempt to reclaim that ground, and he has been unusually candid about how little control a researcher has once a finding enters the press.

Learn More

• Charles W. Eriksen — the flanker task and selective attention, the tradition Stoet's experimental work belongs to
• Anne Treisman — feature integration theory and the study of visual attention
• Harold Kelley — interdependence theory, the framework for analysing dyadic outcomes