And there you go, switching the criterion, from interested bystanders to consensus within a department. The researchers in that department range from a biopsychologist studying pain receptors in mice to a social psychologist studying attraction in couples. They might have different views on the most important concepts and papers.
As for your survey idea (not an experiment), it would be mildly interesting to try it in the other departments in the Science Division, too.
Thank you for admitting my point, even though you apparently don't recognize that you have. In part I suspect that you don't recognize it simply because you don't realize how different the hard sciences are in this respect.
As drkitten notes, I did not switch the criterion. Rather I'm saying that the type of consensus that I'm talking about makes itself obvious in many different ways. Therefore its existence can be seen in many ways. When experts have a compelling case leading to fundamental agreement about what is important, then this becomes something that laypeople notice. When experts agree on which questions are truly key for the field, that shows up in citation patterns that publishers notice. And so on.
FYI, I got the idea for that survey experiment from an actual survey that I heard about many moons ago which was similar to what I suggested. They found no consensus within psychology departments on what was important and substantial consensus within the hard sciences. Which comes as no surprise to anyone who has substantial exposure to those areas.
You've admitted the lack of consensus in psychology. For a contrast go to a math department and ask mathematicians whether they think that Goedel's Incompleteness Theorem should rank in the 10 most important results of math in the 20th century. While you are there, some others that would be good candidates for that list include the discovery of the axiom of choice from the Banach-Tarski Paradox, the classification of finite simple groups, the invention of the notion of a topology, the invention of category theory, and the formalization of Hilbert spaces. No matter what their field, they are likely to agree with the importance of those results. (Though some may point out that there is some doubt that the finite simple groups have really been classified, but that is an issue for another time...)
While you're there ask them whether a top 10 list for discoveries from the 19th century should include the formalization of Calculus (finished in the 1870s IIRC), the Central Limit Theorem, the Prime Number Theorem, the invention of Fourier Series, and Galois' proof of the insolvability of the quintic with ruler and compas. No matter what their field of study, they will probably agree that everything there is important.
I don't know other fields as well as math, but if you're adventuresome, wander over to the biology department. Say that you've heard that the single most important biology paper in the 20th century was the 1953 discovery by Watson and Crick of the structure of DNA. (If you want a copy, see
http://www.fossilmuseum.net/Biology/WatsonCrickNature.htm. Note where it was published...) Ask if this claim is really true. While you're at it ask whether Darwin's Theory of Evolution ranks in the top ideas from the 1800s.
Wander on over to the astronomy department. Say that you heard that 3 of the 10 most important discoveries in astronomy in the 20'th century were Hubble's discovery of the expansion of the universe, Penzias and Wilson's discovery that there was a constant background of microwave radiation from everywhere (which is now interpreted as being left over from the Big Bang), and the paper B2FH (named for the Burbidges, Fowler and Hoyle) on the synthesis of various isotopes in stellar reactions. Ask if this is really true.
Physicists should generally agree that Hahn and Strassman's discovery of fission (with under-acknowledged assistance from Lise Meitner) had a truly immense impact (pun intended) on the 20th century. Their list of top 10 theories from the 20th century will likely include things like relativity (special and general), quantum mechanics, quantum electrodynamics, Noether's theorem and the idea of gauge groups. From the 19th century they'll agree about the importance of Maxwell's equations, conservation of energy, Fourier series and entropy.
And so on.
In short, the consensus that you find in the hard sciences is clear. It is obvious to people in the field. It is visible to bystanders. It is understood by (very importantly for running the journal) Nature's editorial staff. Without that consensus I wouldn't be able to give you example after example of statements about what is important that there is large-scale agreement on. But the consensus exists and I can make those claims. (Feel free to test them if you want.)
By your own words you've admitted the reality that there is no similar consensus in psychology. Until there is, effort may be expended and results established, but the overall result won't look like progress to people outside of psychology. And psychology will continue to not look like a science to people in established sciences. Even though they won't generally be able to give good explanations as to why it is not, they'll know it is not.
Finally let me note that my comment that psychology is not a science is in no way meant to be a criticism of the effort that psychologists have put out. Rather it is a reflection of the fact that the mind is a complex thing - so complex that people haven't been able to reach agreement on how to approach studying it. There are many approaches that seem to get you somewhere, and no agreement on which are likely to be the most productive in the end. Hence the lack of consensus. By contrast the hard sciences have chosen to study more tractable problems and so are able to come to consensus more easily.
Cheers,
Ben