Does the "brain drain" effect really exist?
A 2023 meta-analysis of 22 studies found a small negative effect of smartphone use and presence, driven by memory tasks; the effect on attention was not significant.
The short version
In 2017, a much-cited study suggested that the mere presence of a smartphone reduces available cognitive capacity — the "brain drain" effect. This 2023 meta-analysis pooled 22 studies and found a small negative effect of smartphones overall, driven mainly by memory tasks. On attention specifically, the effect was not statistically significant. It is a more cautious picture than the original headline, and it sits alongside another meta-analysis that found no effect of presence at all.
What the researchers did
Tobias Böttger, Michael Poschik and Klaus Zierer searched the literature for studies testing how smartphones affect cognitive performance. They identified 22 studies containing 43 relevant effects, grouped into three categories: memory, attention and general cognitive performance. Importantly, the analysis covered both smartphone presence and smartphone use, not presence alone. They then compared the categories and looked at other factors, including where the studies were carried out.
What they found
- A small overall negative effect. Across all 43 effects, the pooled estimate was small and negative (Hedges' g = −0.14).
- Memory was hit; attention was not clearly affected. Memory showed a significant negative effect (g = −0.23). The effect on attention was small and not significant (g = −0.07), and general cognitive performance showed no reliable effect.
- Large differences by region. The effect was strongest in samples from Asia and not significant in European or North American samples. The authors did not find a satisfying explanation.
- High heterogeneity. Results varied a lot from study to study, which limits how much any single pooled number can be trusted.
Limits and caveats
Because the analysis mixes phone use with phone presence, it cannot isolate the "mere presence" claim the brain-drain idea is about. Direct replications of the original 2017 study have failed, and a larger meta-analysis focused only on presence — 33 studies and 4,368 people — found no overall effect (Hartanto et al., 2024). The authors themselves call for more research.
What it means for how you work
Treat the "brain drain" as unproven. If anything is affected, it looks like memory rather than attention, and the effect is small. The well-supported reason to put your phone out of reach during focused work is simpler: it removes notifications and the temptation to check, both of which do have evidence behind them (Kushlev et al., 2016). If you are studying or doing memory-heavy work, keeping the phone in another room is a cheap precaution.