A large analysis of around 800 million tweets during a 4-year period suggests that circadian rhythms control our way of thinking.

Our circadian rhythms are known to affect our mood, as our energy levels spike and dip at different times of the day.

But can our internal clocks also affect our way of thinking? Studies have revealed that short-term disruptions in the circadian rhythm can impair our memory, attention, and problem-solving skills.

In the long-term, such disruptions have been linked with mental health disorders, including schizophrenia, bipolar disorder, and depression, lending further credibility to the hypothesis that the sleep-wake cycle might control our thinking.

Now, a study of 800 million tweets brings evidence in support of this theory. Our way of thinking, as well as the underlying emotions, tend to change across the 24-hour sleep-wake cycle, the research suggests.

It was led by Nello Cristianini, a professor of artificial intelligence from Bristol University in the United Kingdom. The findings were published in the journal PLOS ONE.

Analyzing the content of 7 billion words

Professor Cristianini and his colleagues used computer algorithms to sample and analyze 800 million tweets, around the clock, for a period of 4 years. This summed up about 7 billion words.

Of these, the researchers tracked the use of specific words that are linked with 73 psychometric indicators, or measurements of our latent thinking and emotional patterns.

"The analysis of media content, when done correctly," explains Professor Cristianini, "can reveal useful information for both social and biological sciences."

Overall, the study found that at 6 a.m., analytical and logical thinking was at an all-time high. In the evenings, however, the collective thinking style turned into a more emotional and brooding one.

The 5 a.m.–6 a.m. window correlated with nouns suggesting a preoccupation with achievements and power, whereas in the evening the researchers found a more emotional, social, and impulsive thinking pattern.

Finally, between 3 a.m. and 4 a.m., the analysis revealed a correlation with words expressing existential concerns, but an inverse correlation with words indicating positive emotions.

Circadian rhythms may rule our thinking

The study authors suggest that the changes observed are down to our circadian rhythms because they coincide with changes in brain activity and hormonal levels.

Also, the scientists were able to accurately predict thinking and emotional patterns throughout the 24-hour cycle.

As study coauthor Stafford Lightman, a professor of medicine and a neuroendocrinology expert at the Bristol Medical School, explains, "Circadian rhythms are a major feature of most systems in the human body, and when these are disrupted they can result in psychiatric, cardiovascular, and metabolic disease."

"The use of media data," adds Professor Lightman, "allows us to analyze neuropsychological parameters in a large unbiased population and gain insights into how mood-related use of language changes as a function of time of day."

"This will help us understand the basis of disorders in which this process is disrupted," he says.