Nat. Neurosci. 11, 1129–1135 (2008); published online 25 September 2008; corrected after print 13 November 2008

In the version of this article initially published, the legend to Figure 5 contained several errors. The second sentence should read “Fixating on the red minus, you will be unable to identify the middle object in the first eight rows unless you isolate it by hiding the flanking objects with your fingers (or two pencils).” The fourth sentence should read “Grating patches, similar to those in the top row, are often taken to be one-feature objects.” These errors have been corrected in the HTML and PDF versions of the article.