I was trying to remember some quote by the exploratory data analysis master John Tukey yesterday, and I think this is it:
No catalog of techniques can convey a willingness to look for what can be seen, whether or not anticipated. Yet this is at the heart of exploratory data analysis. The graph paper—and transparencies—are there, not as a technique, but rather as a recognition that the picture-examining eye is the best finder we have of the wholly unanticipated.
It is from John W. Tukey, We Need Both Exploratory and Confirmatory, The American Statistician, Vol. 34, No. 1 (Feb., 1980), pp. 23-25.
I remembered a version about the visual cortex as a the most advance signal processing device, so maybe there is another version of this out there.