Sources1 suggest that the frequency resolution of humans—our ability to discriminate differences in pitch—is limited to around five cents.
If this is the case, how can musicians play an excerpt like the following (listen here, and be sure to check out 0:22!), which demands intonation changes of as small as two cents? (The numbers written above/below the pitches are the changes, in cents, for the tuning of each pitch.)
This is spectralist music, so the intonation changes (at least in the first five measures or so) are based on the harmonic series. As such, the first violin may not be thinking of moving the F down two cents, but rather creating a justly tuned minor third with the cello. In other words, the first violinist isn't just tuning their single pitch down two cents, but they're tuning the interval itself. This all makes sense to me, and explains how a musician could hear this particular difference of under five cents.
But if all of this is true, then it seems to suggest that the first violinist can't actually play their part alone without the aid of a tuner. Am I missing something?