  We use the SAMI Galaxy Survey to examine the drivers of galaxy spin,
$\lambda_{R_e}$, in a multi-dimensional parameter space including stellar mass,
stellar population age (or specific star formation rate) and various
environmental metrics (local density, halo mass, satellite vs. central). Using
a partial correlation analysis we consistently find that age or specific star
formation rate is the primary parameter correlating with spin. Light-weighted
age and specific star formation rate are more strongly correlated with spin
than mass-weighted age. In fact, across our sample, once the relation between
light-weighted age and spin is accounted for, there is no significant residual
correlation between spin and mass, or spin and environment. This result is
strongly suggestive that present-day environment only indirectly influences
spin, via the removal of gas and star formation quenching. That is, environment
affects age, then age affects spin. Older galaxies then have lower spin, either
due to stars being born dynamically hotter at high redshift, or due to secular
heating. Our results appear to rule out environmentally dependent dynamical
heating (e.g. galaxy-galaxy interactions) being important, at least within
$1R_e$ where our kinematic measurements are made. The picture is more complex
when we only consider high-mass galaxies ($M_*\gtrsim 10^{11}$M$_{\odot}$).
While the age-spin relation is still strong for these high-mass galaxies, there
is a residual environmental trend with central galaxies preferentially having
lower spin, compared to satellites of the same age and mass. We argue that this
trend is likely due to central galaxies being a preferred location for mergers.
