How people type on their phones could reveal more than just their texting habits. A new study from the University of Illinois Chicago, published in the Journal of Psychopathology and Clinical Science, suggests that patterns in smartphone typing may help detect early cognitive changes associated with depression and bipolar disorder. The findings open a new direction in mental health research, showing how ordinary digital behavior might offer a window into how the brain functions day to day.
Tracking cognition through ordinary behavior
Mood disorders often affect thinking speed, memory, and decision-making. Traditional ways to assess these skills involve paper tests or computer programs that measure attention and flexibility under lab conditions. While effective, these tests require time, controlled environments, and direct participation from patients, which limits how often they can be used.
The research team set out to find whether digital traces from everyday smartphone use could capture the same information without requiring people to take formal tests. They focused on a custom mobile app known as BiAffect, which records metadata about typing behavior... such as the time between keystrokes and the frequency of phone movement during typing.
Over a period of four to five weeks, 127 adults used BiAffect as their default keyboard. Some participants had mood disorders including depression or bipolar disorder, while others were healthy volunteers. Each person completed two in-person lab visits during which they performed standardized cognitive tests, such as the NIH Toolbox and the Trail Making Test Part B, both widely used to evaluate mental flexibility, working memory, and processing speed.
Patterns that reflect thinking speed
Researchers analyzed the data using statistical modeling to find links between typing features and cognitive performance. The two most telling indicators were how quickly people typed and how often they used their keyboard. Faster typing generally reflected sharper processing speed and mental agility.
Among healthy participants, slower typing corresponded with lower scores on the NIH Toolbox tests, while frequent typing was tied to stronger cognitive performance. Together, these digital patterns explained more than forty percent of the variation in thinking ability across the healthy group by the second lab visit.
However, the link between typing behavior and test performance was weaker in participants with mood disorders. Their typing data showed more inconsistency, suggesting that daily fluctuations in symptoms, medication effects, or emotional states may blur the connection between phone behavior and cognitive function.
The Trail Making insight
When the researchers turned to the Trail Making Test Part B — a task that measures mental flexibility and speed by having people draw alternating sequences of numbers and letters... the pattern changed. Typing behavior predicted performance on this test in both groups, regardless of diagnosis. Those who typed more slowly or more frequently tended to take longer to finish the paper test.
As the study noted, “typing speed reliably predicts processing speed and executive function,” and this relationship became stronger as depressive symptoms increased. The result points to executive function (the ability to plan, shift focus, and manage complex tasks) as a domain where digital patterns may reveal meaningful clues.
Why mood affects the link
According to the researchers, cognitive performance in mood disorders may fluctuate more because of symptom changes, stress, or treatment differences. These variations could explain why typing patterns predict cognition more clearly in healthy individuals. The team emphasized that these inconsistencies highlight a need to move beyond simple diagnostic labels and to track symptoms continuously over time.
They also found that people with higher depression scores showed a stronger connection between slower typing and poorer cognitive flexibility. This observation suggests that passive smartphone data might capture subtle changes in brain function as mood symptoms shift, even within the same person.
Limitations and next steps
The study ran for about a month, a relatively short period for detecting long-term changes in cognition. Most participants were well educated, which might have helped them compensate for mild impairments. Future research, the authors noted, will need longer monitoring and more diverse participants to understand how generalizable these results are.
The researchers acknowledged that not all mental skills can be detected through typing. The NIH Toolbox includes different types of tasks, and not all depend on the same cognitive processes involved in typing. That means smartphone data may be best suited for tracking certain abilities, such as processing speed and executive control, rather than overall intelligence or memory.
Everyday technology as a mental health tool
Despite its limits, the study demonstrates the potential of passive digital monitoring to complement traditional neuropsychological testing. Because people type on their phones many times a day, this approach could allow for continuous observation without disrupting normal routines.
The authors described smartphone data as “an ecologically valid, passive measure of cognitive function” that could help clinicians notice changes earlier than conventional tests. Subtle shifts in typing rhythm, for example, might one day alert healthcare providers that a patient’s thinking speed is slowing or that a depressive episode may be developing.
Using such methods could reduce the need for frequent clinic visits and enable personalized care. For patients living with mood disorders, it might also offer reassurance that their everyday actions (like texting a friend or writing a note) carry information that can support their treatment in real time.
The broader meaning
What makes this research stand out is how it connects routine digital behavior to the complexity of human cognition. Rather than relying solely on lab-based tools, it recognizes that our smartphones have become constant companions that record subtle aspects of how we move, think, and interact.
The researchers view typing as more than a habit... it is a reflection of mental coordination involving attention, planning, and motor control. If analyzed responsibly and ethically, such data could help identify changes long before they become visible in clinical settings.
The study adds to a growing field known as digital phenotyping, where everyday technology is used to understand patterns of behavior and mental health. It suggests that one day, how we type might quietly tell a story about how our brains are coping, adapting, or recovering... a story written in every keystroke.
Notes: This post was edited/created using GenAI tools.
Image: Faustina Okeke - unsplash
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