An investigation into what people think about has put the spotlight on the modern mind, revealing thoughts dominated by work, the need for coffee and a strong desire to go back to bed. It also found evidence for four distinct groups of thinkers who spend more time than most either worrying about the world; mulling on household chores and finances; focusing on the mind and body; or the work-hard, play-hard combination of career and pleasure. The groups are not definitive and people will move between them, but the finding shows how sampling people’s thoughts at random can provide a nuanced view of human thinking patterns, according to the researchers.

Economists at Claremont Graduate University, in California, and Wuhan University, in Hubei, China, explored people’s conscious thoughts after finding a surprising dearth of work on the topic. “So much of what it means to be human is about what’s going on in our head,” said Dr Joshua Tasoff, a senior author on the study. “The fact that we haven’t really looked at that as economists is really quite extraordinary.” For the study, 258 volunteers aged 19 to 71 downloaded an app that beeped at eight random times per day for two weeks.

On each beep, they were required to write down their thoughts, what they were doing and rate their happiness level. After gathering more than 23,000 real-time responses, the economists saw that people’s thoughts flowed with the rhythms of the day, steered largely towards work in the day and entertainment in the evening. Roughly half of people’s thoughts were intentional, the rest being intrusive or accidental thoughts from mind wandering or reminders.

Sensory information, including feeling tired and sleepy, and mental impressions, accounted for nearly a fifth of all thoughts. Next came work at 17% and food at 14%. About 10% of thoughts centred on hobbies, games, play and art, with a similar amount focused on relationships.

When thoughts centred on what people wanted, nearly half involved food or drink, especially coffee. This chimed with thoughts that mentioned needs, with 29% seeking relaxation, and naps and sleep in particular. The mind was rarely blank, the study found, with only a fraction of a per cent of responses claiming no thoughts at all.

However, even fewer thoughts appeared to be about sex, leading the researchers to suspect reticence. “There may be things people don’t want to share with us. You know: TMI [too much information],” Tasoff said.

Perhaps related, a quarter of beeps went unanswered, according to a preprint of the study, which has yet to be published in a peer-reviewed journal. Part of the study tested an assertion by the Roman emperor and philosopher Marcus Aurelius, who said: “The happiness of your life depends on the quality of your thoughts.” The researchers found that what people were thinking was more predictive of their happiness than anything else they looked at. “Maybe Marcus Aurelius was on to something,” they said.

The authors cautioned against extrapolating the findings to the global population because the psychology of the volunteers, all classified as western, educated, industrialised, rich and democratic – or Weird – could differ dramatically from other populations.