an -> and

main.tex

@@ -860,7 +860,7 @@ \section*{Acknowledgements}
 assist bicycle. We acknowledge Shannon van de Velde and Marco Reijne's
 development of the bicycle perturbation system. Allen Downey provided useful
 insight in the statistical condsiderations. We thank all of the assistants that
-helped run the experiments and the participants for their time an enthusiasm.
+helped run the experiments and the participants for their time and enthusiasm.
 Thanks to Christoph Schmidt for motivation to do yet another round of trials.
 We thank Peter Stahlecker, Benjamin Gonzalez, and Riender Happee for valuable
 feedback in early revisions. Lastly, we thank Frans van der Helm for the