Extrovert or introvert, big idea or detail-oriented, artistic or analytical — all of these traits and more are ways that humans’ personalities differ from one another. The amount of research that has gone into why humans act the way they do is extensive, but a new study adds another layer to the mystery of human nature — sleep preferences.
When talking about sleep preference, this biological trait is often referred to as a chronotype. This is the aspect of genetics that causes people to be an early bird or night owl. In addition to regulating sleep and wake times, chronotypes have an influence on several other daily functions, such as appetite and body temperature. According to scientists, adjusting one’s chronotype is difficult or nearly impossible, which makes it a crucial piece of the personality puzzle.
According to a study conducted by the Estonian Ministry of Education and Science, chronotypes and personality types were significantly associated at every level of a personality hierarchy. The study sampled roughly 2,500 Estonian adults by having them ask a person they knew well to answer a questionnaire about them. The study used genetic and personality data made available through the Estonian Biobank, while also asking participants to track their sleep. The personality traits the study looked for were that of the NEO-PI-3 test, which measures a person’s ranking in the following traits: neuroticism, extraversion, openness to experience (openness), agreeableness, and conscientiousness.
The results of the study found that morningness–eveningness and personality were significantly genetically correlated with each other and that the person’s sleep tendency consistently predicted their personality scores, according to the five traits. Participants with high levels of extraversion and openness had later chronotypes, meaning the night owls were more likely to be open to new ideas and people, while the early birds showed higher scores of agreeableness and conscientiousness. These results line up with the understanding that morning people tend to have an easier time adjusting to societal schedule obligations, and that a morning-centric society could be a challenge for a night owl. Morning people typically have an easier time being conscious of time management and are less likely to be late, which explains why they see higher scores in conscientiousness. Interestingly, the night owls’ constant need to wake up earlier than desired may play into their tendency to be more open.
The findings didn’t just stop at day-to-day facts about its participants — it went as far to predict things that may happen in the future based on a person’s chronotype. The night owls who participated in the study typically scored low on the sub-category of self-control, which has been previously linked to eveningness. This means that those who are prone to waking early are statistically less likely to develop a substance dependence, as well as fewer criminal offending outcomes. This isn’t to say that all hope is lost for the night owls — self-control interventions have been proven to work well on those who had previously scored low in that category, thanks to their tendency to be more open to change. This means societal pressures, such as a family or job, could greatly impact the probability of a more negative outcome due to chronotype.
While there is no right or wrong way to sleep, the findings of this study show that there is more than meets the eye when it comes to the human body’s natural preferences. It’s important to be mindful of biological preferences, especially for those who have to go against their body’s natural clock to adhere to societal obligations. Improving sleep quality or adjusting one’s sleep environment can help improve the hours spent sleeping, which will ultimately lead to a happier and more functional life.