But a question has lingered: does this bias hit everyone equally, or are some people naturally more resistant to the siren song of a recent win? A new study published in the Journal of Research in Personality suggests the answer depends a great deal on who you are. By linking real betting records to personality tests and intelligence scores, researchers found that higher IQ and conscientiousness tend to buffer against the effect, while extraversion amplifies it.
A rare matching of real bets to real traits
Led by Jussi Palomäki of the Finnish Institute for Health and Welfare, the research team pulled off something unusual: they combined three sizable datasets that Finland’s administrative systems made possible. The first was a year’s worth of online horse race betting records from Veikkaus, the state-owned gambling monopoly. The second was socioeconomic information from Statistics Finland’s national registry. The third was cognitive ability and personality test data collected decades earlier by the Finnish Defence Forces, which tests nearly all male conscripts.
When the datasets were matched at the individual level, the team had 11,220 men aged 36 to 54 whose day-to-day betting behavior could be connected to trait measurements taken years before they placed any of these bets. Because Finnish military service is mandatory for men, the sample avoided the self-selection problems that plague voluntary personality surveys.
The researchers measured the house money effect two ways. First, they looked at how much a person wagered on a given day based on whether they had come out ahead on their previous betting day. Second, they tracked how many days passed before a bettor returned for another session. The logic: someone riding high on a win should bet more, and come back sooner.
The pattern in the raw numbers
Before any statistical modeling, the basic averages told a clear story. On days following a winning session, the average bet was about €72. On days following a losing session, it was around €48. The gap in return time was even sharper. After a win, bettors came back in under two days on average (the median was less than two days). After a loss, they took nearly seven days to return.
The regression analysis confirmed the pattern held after controlling for socioeconomic variables, day of the week, and month. Winning on the previous day was associated with a 45 percent jump in the amount wagered the next time, and a roughly 16 percent shorter gap between sessions. The house money effect, in other words, was alive and well in this naturalistic setting.
Where personality and intelligence come in
The more interesting findings emerged when the researchers examined how the effect varied across people. They looked at three trait dimensions: general intelligence (a composite IQ score from numerical, verbal, and spatial reasoning tests), conscientiousness (which captures discipline, dutifulness, and careful deliberation), and extraversion (which captures sociability, energy, and reward-seeking).
For bettors scoring two standard deviations below the mean on IQ, winning the previous day was associated with a 58 percent jump in the next day’s bet size. For those two standard deviations above the mean, the jump was only 35 percent. Conscientiousness showed a nearly identical pattern: low-scoring bettors increased their bets by 55 percent after a win, while high-scoring bettors increased theirs by 33 percent.
Extraversion ran the other way. Highly extraverted bettors showed a 58 percent post-win jump, while introverted bettors showed only 34 percent. The same pattern appeared in how quickly people returned to betting. Bettors lower in IQ and conscientiousness, and higher in extraversion, came back faster after a win.
To put it in money terms, after a winning day, a bettor with very low IQ wagered about €75 on average, while a bettor with very high IQ wagered about €64. The differences aren’t enormous on any single day, but they compound over a year of repeated decisions.
Why these traits in particular?
The authors interpret the findings through several overlapping lenses. Extraversion has been linked in earlier research to reward sensitivity and optimism, which may translate into overconfidence after a win. Conscientiousness is associated with self-control, effortful regulation, and a stronger emotional aversion to losses, any of which could dampen the urge to ride a winning streak. Higher intelligence has been connected in prior studies to reduced susceptibility to cognitive biases more generally.
Interestingly, when the researchers added a variable for the size of previous winnings, it didn’t significantly predict subsequent behavior. What mattered was simply whether the bettor had come out ahead, not by how much. The authors suggest this points toward a psychological rather than strictly financial mechanism: the feeling of winning, more than the amount, is what loosens the wallet.
Caveats worth keeping in mind
The authors are careful about what their data can and cannot show. The personality and IQ measurements were taken 16 to 35 years before the betting data, so any observed effects speak to the stability of these traits rather than momentary states. The sample is entirely male and Finnish, and drawn from a specific age range, so generalization to women or other populations requires caution. The study is also limited to horse race betting, which has its own quirks and skill elements that may not carry over to other financial domains.
The effect sizes, while statistically robust given the huge sample, are modest in any single comparison. As the authors note, though, small effects can accumulate into meaningful consequences when people make hundreds of financial decisions over time.
What it means for the rest of us
For gambling operators and regulators, the findings add to growing evidence that certain individuals are more behaviorally vulnerable to escalating risk after wins, which could inform how responsible gambling tools are designed. For individual investors and bettors, the more general lesson is one that financial advisors have been preaching for a long time: after a good run, it pays to be aware that your next decision may be colored by the one that just went well. And that awareness may matter more for some personalities than others.
The study also offers a broader point about research methods. Much of what we know about cognitive biases comes from lab experiments with small stakes and self-selected participants. By matching real betting behavior to pre-existing trait measurements, the researchers were able to watch a classic bias play out with actual money on the line, and to show that who you are shapes how much it moves you.
