did grayscale phones cut daily use by an hour? the study isn't public
“we saw on average people spent 1 hour less on their phones every single day.”
a guest, a cognitive neuroscientist said on The Diary of a CEO, 2026-10-15, at 46:34. hear it in context → the speaker cited: her own lab's unpublished research.
first, the part that holds
grayscale mode does cut phone use in controlled studies. published trials we read found daily screen time went down when phones were set to grayscale, so the direction of the claim matches the record.
what we found when we went and looked
the speaker said the 1-hour figure came from their own lab's unpublished work. we found no paper, preprint, trial registration or dataset for a 3-week grayscale study in healthy working professionals, so the number can't be checked. the published trials we read point the same way but report smaller drops: a 2026 crossover trial in 51 medical students found about 28 minutes less per day (347.29 down to 318.87 minutes, p = 0.0243), and a 2023 randomized field experiment found an immediate, significant drop in objectively measured screen time. none of the published work we read reports a reduction near 60 minutes, and none studied working professionals or a 3-week grayscale period.
assertion by assertion
| assertion | verdict | what the record says |
|---|---|---|
| in the speaker's study, average daily phone use fell by about 1 hour when phones were set to grayscale | unverifiable | the source is described as unpublished lab research. we found no paper, preprint, registration or data file, so there is no sample size, baseline, control group or variance to check the 1-hour mean against. |
| the study population was healthy working professionals and the grayscale period lasted 3 weeks | unverifiable | no public record of the study design exists. the published grayscale trials we read enrolled students (medical, undergraduate, pharmacy) and ran grayscale phases of roughly 1 week, not 3. [1] |
| setting a phone to grayscale reduces daily screen time | confirmed | a 2026 crossover trial (n=51 medical students, 1 week per condition) found about 28 minutes less per day in grayscale (p = 0.0243). a 2023 randomized field experiment found grayscale gave an immediate, significant drop in objectively measured screen time compared with control. both studied students, ran for short periods, and one was a feasibility trial. [1][2] |
| a drop of about 60 minutes a day is in line with the published grayscale literature | overstated | the published effects we read are smaller: about 28 minutes per day in the 2026 trial. a widely cited undergraduate study (reported elsewhere as about 38 minutes per day) was paywalled, so we could not read its figures ourselves. we found no published estimate near 60 minutes. [1] |
both directions
for the speaker: every controlled grayscale study we read found screen time went down, including a randomized field experiment with objectively measured use. the 2026 crossover trial is consistent with that earlier work. a longer intervention, adults with different phone habits, or a heavier-use baseline could plausibly give a larger absolute drop than week-long student studies. on 347 minutes of baseline use, a 60-minute cut would be about 17 percent.
against: the 1-hour figure has no public methods, sample size, control condition or measure of spread. the published estimates we read are about half that size or less. the randomized field experiment found no immediate causal effect on subjective well-being or academic performance, so less screen time did not translate into measurable well-being gains there. the 2026 trial reported people switching to other devices and trouble with apps that depend on color. that means phone-only screen time could overstate the real drop in total screen use.
what this cannot say
we can't evaluate data that hasn't been released. if the lab publishes, the verdict on the 1-hour figure could change in either direction. the published trials are small and short and mostly enroll students, so they say little about working professionals over 3 weeks. two relevant papers (a 2020 undergraduate study and a 2023 well-being study) were paywalled or blocked when we tried to fetch them, so we did not cite their numbers. the effect on ongoing mental-health outcomes is not established by any of this work.
sources, each one fetched and read
- A cross-over feasibility trial of smartphone grayscale mode in medical students. Frontiers in Digital Health, 2026. doi:10.3389/fdgth.2026.1816095 What we read there: 51 of 61 enrolled medical students completed a two-week crossover (1 week per condition); mean daily screen time went from 347.29 minutes in color to 318.87 minutes in grayscale, a reduction of about 28 minutes per day (p = 0.0243). prior grayscale studies cited were in college and pharmacy student populations. Fetched 2026-10-27 (HTTP 200). https://www.frontiersin.org/journals/digital-health/articles/10.3389/fdgth.2026.1816095/full
- PubMed abstracts, PMID 36577008 (Digital strategies for screen time reduction: a randomized field experiment. Cyberpsychology, Behavior, and Social Networking, 2023. doi:10.1089/cyber.2022.0027) and PMID 42518736 What we read there: the design friction intervention (activating grayscale mode) led to an immediate, significant reduction of objectively measured screen time compared with control; no immediate causal effect of reducing usage on subjective well-being and academic performance was found. the 2026 trial abstract reports a mean reduction of 28 min per day. Fetched 2026-10-27 (HTTP 203). https://pubmed.ncbi.nlm.nih.gov/36577008/
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