Inconsistent refresh rate on Apple M1 Max

Hello everyone,

We’re running an experiment using a priming paradigm with: 33ms primes (2 frames) and 500ms targets (30 frames) that should (supposedly) work with a 60Hz refresh rate.

However, after analysing the presentation duration of both primes and targets, we uncovered a major anomaly in the refresh rate values. Not only is the refresh rate different from 60Hz, but it also seems to vary from stimulus to stimulus.

We have a MacBook Pro 16-inch 2021, with an Apple M1 Max chip with 32 cores
We’re using PsychoPy version 2022.2.5
We already set the refresh rate in the Mac to 60Hz in System Settings > Displays > Refresh rate

Here are two elements to illustrate the refresh rate anomaly:

(1) Example of a log file from PsychoPy. It is interesting to note the pattern of dropped frames isn’t at all consistent among the participants (+/- 30): sometimes we only have two dropped frames, sometimes the right refresh rate is 60Hz, and sometimes the refresh rate is impossible to calculate.

122.5314 WARNING t of last frame was 24.50ms (=1/40)
122.5940 WARNING t of last frame was 21.16ms (=1/47)
122.8491 WARNING t of last frame was 25.81ms (=1/38)
122.8781 WARNING t of last frame was 22.74ms (=1/43)
122.9772 WARNING Multiple dropped frames have occurred - I’ll stop bothering you about them!
123.1368 WARNING Couldn’t measure a consistent frame rate!

  • Is your graphics card set to sync to vertical blank?
  • Are you running other processes on your computer?

(2) Example of the variable refresh rate for the (100) primes presented to a participant:

Has anyone encountered this problem before? Any help is greatly appreciated.
Thanks a lot,


Hi Chloe,
I have encountered the same issues on my M2 Mac. From my googling people suggested to set the refresh rate from ProMotion to 60Hz on settings, but that did not solve the issue. Have you figured out a way to deal with this?
Thank you!