When someone says a paper is published "in Nature", does that mean it's published in *Nature*?

I've never heard a neuroscientist say they published in Nature, if it was in Nature Neuroscience.

The answer to your question is probably "Yes and No" or, more properly, it depends on who is telling you this and why.

If the individual wants you to find his or her research, then "in Nature" might mean in Nature. However, if someone wants you to find research, why aren't they giving you a full citation?

Usually someone would say their work is published "in Nature" to make themselves sound important (sometimes rightfully so). In this case, I doubt that the individual would make a distinction between Nature and the derivative journals, most of which also have high impact factors. The person is more likely to be vague if the field-specific NPG journal in which the work is published has a much lower impact factor than Nature.

In the field of chemistry, Nature Chemistry is relatively new, 4 years old. Since NChem is so new, most folks I talk to distinguish whether they mean Nature or NChem. NChem's newness leaves it with a lower impact factor (20.524 for 2011, the first year it qualified for one) vs. Nature (36.280 in 2011).

This Nature guide to authors uses the phrase "Nature and the Nature research journals." Also, the editorial policies website states

The Nature journals' editorial policies concerning publication of primary scientific research can be found on the pages listed below. The policies described are those of Nature and the journals with "Nature" in their titles.

This implies that when the Nature Publishing Group uses the word "Nature" in italics, they are referring to the journal Nature and not to their other journals. If they want to refer to any of their journals, they use the phrase "Nature journal" (without italics).