Recent research published in journals psychological science This suggests that a single dose of testosterone does not cause men to follow their intuition and abandon deliberate reasoning. In fact, contrary to previous assumptions, this hormone can actually make people less confident in their own cognitive abilities. These findings provide evidence that short-term spikes in testosterone do not significantly alter decision-making in this particular type of human.
The human brain can solve problems using fast, intuitive thinking or slow, deliberate reasoning. Psychologists often measure this tendency using cognitive reflexivity tests. This test is an assessment in which you are presented with an obvious but mathematically incorrect intuitive answer to a question. To arrive at the right solution, you need to pause and override your initial gut reaction.
Testosterone is a sex steroid hormone that dynamically responds to social and environmental changes. In both animals and humans, testosterone levels can rise rapidly in competitive or mating situations. This environmental responsiveness forms the basis of the challenge hypothesis, a biological theory that proposes that testosterone modulates behavior in a situational manner, promoting fast-acting instinctive behavior under social threat.
Translating this biological theory to human cognition has led to certain hypotheses regarding decision-making. Previous researchers have proposed that temporary increases in testosterone can shift judgment toward intuitive responses. An influential 2017 paper reported just this effect, finding that administering testosterone significantly reduced scores on cognitive reflex tests.
Subsequent follow-up studies yielded inconsistent or completely invalid results, causing confusion in the scientific community. To settle the dispute, scientists who wrote contradictory papers came together to engineer an adversarial collaboration. This is a research project in which scientists with opposing views work together to design a definitive experiment.
Gideon Nabe, the Carlos and Rosa Dela Cruz Associate Professor of Marketing at the Wharton School at the University of Pennsylvania, helped organize the collaborative effort. “The original idea came from evolutionary biology and neuroscience,” Neve said. “In situations such as competition or mating, testosterone increases. In these situations, acting quickly and instinctively rather than carefully considering it may be more adaptive. Therefore, we hypothesized that temporary increases in testosterone may make people more reliant on intuitive reactions and reduce cognitive reflection.”
“While initial experiments in 2017 supported that idea, subsequent studies have yielded different results,” Nabe added. “Rather than argue over which study was correct, the various research teams decided to work together in an adversarial partnership. Despite reaching different conclusions, we remained collegial and together we designed the largest and most rigorous study we could conduct to fully resolve the problem.”
The team pre-registered the method. That is, we published our exact plans and hypotheses before collecting data. The research team recruited 1,000 adult men between the ages of 18 and 45. This study used a double-blind, randomized, placebo-controlled design. This meant that neither the participants nor the research assistants distributing the doses knew who received the actual hormone and who received the inert substitute.
Half of the participants self-administered an intranasal testosterone gel that delivered 11 milligrams of the hormone directly into their nose. The remaining 500 men received a placebo gel that looked and felt identical. After a 30-minute waiting period for the hormones to enter the bloodstream and reach a higher range of physiologically normal values, the men completed various behavioral tasks.
The primary task of interest was a modified seven-item version of the Cognitive Reflexivity Test. The authors used a reworded version of a classic test to ensure that participants had never seen a particular puzzle on the Internet. To keep participants motivated, the scientists offered a $1 cash bonus for each correct answer. After the test, the men guessed how many of the seven questions they answered correctly.
Test scores did not support the initial hypothesis in 2017. The researchers found no statistically significant differences in test performance between the testosterone and placebo groups. Men given testosterone answered an average of 3.01 questions correctly, compared to 2.86 for those in the placebo group.
When analyzing self-reported confidence ratings, the researchers found another unexpected result. The researchers initially predicted that testosterone would make men even more overconfident in their performance. Instead, the data showed a significant drop in self-confidence in those who received the hormone. Men in the testosterone group estimated they answered fewer questions correctly compared to estimates made by the placebo group.
“Not only were we unable to reproduce our original findings, but the estimated effects were actually in the opposite direction,” Naab told SciPost. “We also found evidence that testosterone reduces self-confidence, rather than increasing it, which is contrary to many existing theories. Because this finding was unexpected, we believe it should be interpreted with caution and independently replicated before strong conclusions can be drawn.”
The researchers also examined whether the treatment changed how participants viewed their abilities compared to others. They asked participants to guess how many questions the average participant in the study answered correctly. Relative confidence scores were then calculated by subtracting participants’ guesses about the average person’s score from their own self-estimated scores. The data showed that both groups overestimated their performance compared to the other group, and that testosterone treatment did not significantly change this difference.
In addition to the main experiment, the authors performed several exploratory analyzes based on participants’ natural hormone levels. They defined baseline testosterone as the naturally occurring level of the hormone in the initial saliva sample. Researchers found a negative association between natural baseline testosterone and test performance. Men with naturally higher baseline testosterone tended to score slightly lower on cognitive reflex tests.
Scientists also focused on cortisol, a hormone closely associated with stress. They found suggestive evidence of a positive interaction between baseline cortisol levels and testosterone treatment on test performance. They also tested whether humans’ innate impulsivity changes their response to hormone doses. Previous research has suggested that testosterone may impair performance in men with low impulsivity, but in the current large sample, we found no evidence of an interaction between personality traits and treatment.
Readers should be aware of several limitations when interpreting these findings. The study included only adult men, limiting the ability to generalize the results to a broader population. Men and women process and respond to sex steroid hormones differently. Future studies should also include female participants to see if these null results hold across different populations.
There are also limitations on the exact timing and dosage of hormone administration. The researchers waited 30 minutes after administering the nasal gel before starting the behavioral task. Although evidence to date supports a rapid timescale for the effects of testosterone on behavior, it remains possible that testosterone influences cognitive reflection over a much longer time frame.
This study only looked at short-term, sudden spikes in hormone levels. Long-term administration of testosterone may differentially affect cognitive reflection. Chronic exposure can cause neural structural changes that are quite different from those observed in single-dose experiments.
“Our study examined the effects of a single, short-term increase in testosterone in healthy men,” Nave told PsyPost. “There is no mention of long-term testosterone exposure, hormone replacement therapy, or the effects of testosterone during critical developmental periods such as adolescence. All of these may have different outcomes, but are much more difficult and often impossible to study experimentally.”
Looking ahead, researchers plan to continue exploring the limits of behavioral endocrinology. “One important direction is to understand how hormones do and do not influence cognition and behavior,” Neve said. “Our findings suggest that temporary increases in testosterone do not meaningfully change people’s ability to override intuitive responses and make deliberate inferences.”
The research team hopes their methodological approach will inspire other scientists faced with contradictory data. Nave hopes this project will foster adversarial collaboration in the behavioral sciences. “Researchers are being asked to put aside their obsession with previous discoveries and focus on designing the strongest possible tests for scientific questions, which will ultimately benefit the entire field,” he said.
“For me, one of the most important aspects of this project is the process, not just the results,” says Nave. “This study brought together researchers who had previously published conflicting research results, but we shared a common goal of finding the right answer rather than defending previous research.”
“We agreed on the design and analysis plan before looking at the data, and I think this type of collaboration provides a model for how science can efficiently resolve important disagreements,” Naab added. “More broadly, I hope people see this study as an example of science working the way it should. Different labs can get different results, but the best way to resolve those disagreements is not through debate, but rather by working together on larger, more rigorous studies that everyone agrees on in advance.”
The study, “Does Testosterone Affect Cognitive Reflexes? Evidence from a Double-Blind, Randomized Controlled Study of 1,000 Participants,” was conducted by Eric L. Knight, Gideon Neve, Stephen D. Shaw, Koren Apicella, Pierre L. Bonin, Anna Drever, Sean N. Genior, Magnus Johannesson, and Dylan. Manfredi, Pranhar Mehta, Valentina Proietti, Stephen J. Stanton, Francesca R. Ruberti, Triana Ortiz, and Justin M. Carre.
