  Using SPITZER 3.6$\mu$m imaging, we investigate the physical and data-driven
origins of up-bending (Type III) disk breaks. We apply a robust new
break-finding algorithm to 175 low-inclination disk galaxies previously
identified as containing Type III breaks, classify each galaxy by its outermost
re-classified (via our new algorithm) break type, and compare the local
environments of each resulting subgroup. Using three different measures of the
local density of galaxies, we find that galaxies with extended outer spheroids
(Type IIIs) occupy the highest density environments in our sample, while those
with extended down-bending (Type II) disks and symmetric outskirts occupy the
lowest density environments. Among outermost breaks, the most common origin of
Type III breaks in our sample is methodological; the use of elliptical
apertures to measure the radial profiles of asymmetric galaxies usually results
in features akin to Type III breaks.
