[Schneed10]

In reality, the manner of discipline (time outs vs spanks) is not going to have a huge influence on a child's development. Socioeconomic status, parental guidance and support, genetics, and the peer influences are much bigger factors. As long as the child isn't handled at either end of the discipline spectrum (beaten abusively or allowed to do whatever sans consequences), they'll pretty much turn out the way their situation dictates.

It's much more important as a parent to ensure they're hanging around the right kids than it is to fuss over whether to spank or whether to give timeouts.