The survey asked:

"Just off the top of your head, would you say you have a positive or negative image of each of the following? (Small business, Free enterprise, Capitalism, Socialism, Big business)"

So these terms are left as self-explanatory. In the US, "socialism" covers a huge amount of ground (from any government program at all, all the way to Soviet style communism.) So who knows what items people were picking.

One thing that is interesting, look at the gender and age splits in the above link for "socialism" and "capitalism" - 15-20 point divide between genders overall, and I bet the split is even more stark among young people.