  Recent observational literature suggests that only a small number of
colliding galaxies show substantial star formation enhancements before merging.
Most have SFRs comparable to those of late-type field galaxies. Preliminary
Spitzer studies (with data from the Spirals, Bridges and Tails and SINGs
projects) generally confirm this, though with some caveats. If star formation
in isolated disks is self-regulated, while collisions disequilibrate much of
the disk, then the similarity to star-formation in isolated disks is
surprising. Comparisons of observations and dynamical models suggest some
resolutions to this paradox, including the role of downsizing. The interesting
example of the Arp 82 system is presented.
