People use their smartphones for an average of five hours a day - about a third of the time they are awake - and check them about 85 times a day, research suggests.
The study in the journal PLOS ONE compared the amount of time participants estimated they spent on their smartphones with their actual usage.
It found that people were accessing their phones twice as often as they thought.
Dr David Ellis, a psychologist at Lancaster University, said: "Psychologists typically rely on self-report data when quantifying mobile phone usage in studies, but our work suggests that estimated smartphone use should be interpreted with caution."
The researchers argue that 'rapid mobile phone interactions' are becoming habitual for smartphone users. They asked 23 participants, aged 18-33, to estimate how much time they had spent on their phone.
An app was also installed on their smartphones which recorded all their actual usage over a two week period. This included activities like checking the time, looking at message notifications or social media alerts, phone calls and playing music.
Researchers found that smartphone use was typically confined to short bursts - more than half of uses lasted less than 30 seconds.
The study was led by Lancaster University with Nottingham Trent, the University of Lincoln and University of the West of England.