In Bloom's taxonomy, evaluation is the highest ordered thinking skill in the cognitive domain. If you want to assess how a person thinks or how much a person knows, ask him to grade a piece of work and explain how he arrived at the rating. You'll be able to tell from his evaluation if he thought deeply about the work, is widely read in the domain, is pushing an agenda or perspective, or is only fixated on grammar and formatting.
I'm very self-concious, therefore, when I am asked to review the work of other people for possible publication in a journal or inclusion in conference proceedings. Each review is a test. Although the author will probably never know who I am, the editor will, and he or she will see first hand just how brilliant or bobo I can be.
I therefore try (some times harder than others, admittedly) to comment about the work I'm given in layers. On the surface, I try to comment on grammar, format, and organization. Going slightly deeper, I comment on whether the literature cited is relevant, or if there are other works that might be more apt. I try to understand the design of experiments, and see if they are reasonable. If I'm feeling really macho, I try to comment on the data analysis treatments, to determine if they were executed correctly and evaluated using valid methods (this is the area in which I'm the least confident). Finally, I read the conclusions and decide whether it is fair for the authors to have drawn them.
Seeing as I have a system for reviewing, I wish I could say that all my reviews are brilliant and insightful. The fact is, though, that my reviews are still very much limited by my own knowledge base. There have been cases in which I've returned papers to editors, saying that I didn't have the qualifications to provide a credible review. I'm picky about what I'll read, and am becoming pickier as I age. The fear of making a fool out of myself is growing with time. I think that's precisely because, as you age, people have greater and greater expectations about the quality of your work, and if you fall below expectations, you are somehow ... diminished.
In the review process, it is not only the papers that are evaluated. So are the reviewers.
