  We present Gemini/GNIRS cross-dispersed near-infrared spectra of 12 nearby
early-type galaxies, with the aim of testing commonly used stellar population
synthesis models. We select a subset of galaxies from the atlas/ sample which
span a wide range of ages (SSP-equivalent ages of 1--15~Gyr) at approximately
solar metallicity. We derive star formation histories using four different
stellar population synthesis models, namely those of [bruzual_stellar_2003],
Conroy, Gunn \& White (2009; 2010), [maraston_stellar_2011] and
[vazdekis_uv-extended_2016]. We compare star formation histories derived from
near-infrared spectra with those derived from optical spectra using the same
models. We find that while all models agree in the optical, the derived star
formation histories vary dramatically from model to model in the near-infrared.
We find that this variation is largely driven by the choice of stellar spectral
library, such that models including high quality spectral libraries provide the
best fits to the data, and are the most self-consistent when comparing
optically-derived properties with near-infrared ones. We also find the impact
of age variation in the near-infrared to be subtle, and largely encoded in the
shape of the continuum, meaning that the common approach of removing continuum
information with a high-order polynomial greatly reduces our ability to
constrain ages in the near-infrared.
