It's not that I'm so smart, it's just that I stay with problems longer

We searched Einstein's authored writings, published correspondence in The Collected Papers of Albert Einstein, recorded interviews, and standard biographies such as Walter Isaacson's Einstein: His Life and Universe, and found no primary source in which Einstein wrote or spoke this exact sentence. Alice Calaprice, the most rigorous cataloguer of Einstein sayings, includes it in The Ultimate Quotable Einstein as an attributed remark rather than a documented, sourced quotation, and Quote Investigator traced its appearance in print to at least 1996, in a syndicated L. M. Boyd column — which shows the attribution is not a recent invention but stops short of supplying primary evidence. The line circulates widely in books and motivational literature (Peter Atkins, Richard St John, Michael C. Sherrad, and many others all reproduce it as Einstein's), yet all of these simply repeat the attribution without a traceable citation, and the wording drifts between variants ("It's not that I'm so smart..." / "I'm not smarter, I just stay with problems longer"), a pattern typical of unsourced sayings. A full-text check of Einstein-credited volumes turned up no verbatim match, though gaps in digitized speeches, letters, and older books mean that absence settles nothing on its own. Crucially, we found no reputable source naming an alternative author, and no documented instance of the line predating Einstein and credited to someone else, so there is neither positive evidence of misattribution nor a genuine authorship dispute — only near-universal credit to Einstein with no confirming primary record. We are marking this quotation as attributed.