  We study the dependence on configuration in momentum space of the primordial
3-point function of density perturbations in several different scenarios:
standard slow-roll inflation, curvaton and variable decay models, ghost
inflation, models with higher derivative operators and the DBI model of
inflation. We define a cosine between the distributions using a measure based
on the ability of experiments to distinguish between them. We find that models
fall into two broad categories with fairly orthogonal distributions. Models
where non-Gaussianity is created at horizon-crossing during inflation and
models in which the evolution outside the horizon dominates. In the first case
the 3-point function is largest for equilateral triangles, while in the second
the dominant contribution to the signal comes from the influence of long
wavelength modes on small wavelength ones. We show that, because the
distributions in these two cases are so different, translating constraints on
parameters of one model to those of another based on the normalization of the
3-point function for equilateral triangles can be very misleading.
