Insert \par inside the {\LARGE...} group and remove the line break at the end, since "There's no line here to end." Or, just drop the group formatting entirely, letting the font selection be scoped by the center environment:
\documentclass{article}
\begin{document}
\begin{center}
{\LARGE\bfseries An \textit{a priori} Typology of Sentential Negation from an HPSG Perspective}
\end{center}
\begin{center}
\LARGE\bfseries An \textit{a priori} Typology of Sentential Negation from an HPSG Perspective
\end{center}
\end{document}
The motivation here is that TeX only sets a paragraph once it's fully read it. So, without a blank line or an indication like \par the paragraph isn't set correctly with the change in \baselineskip.
Please note that the \it, \bf, etc. font macros are deprecated because
they do not use the new font selection scheme introduced with LaTeX2e.
Please use {\itshape ..}, {\bfseries ..} or \textit{..}, \textbf{..} instead.
See Does it matter if I use \textit or \it, \bfseries or \bf, etc.
and Will two-letter font style commands (\bf, \it, …) ever be resurrected in LaTeX?
for more information.
With your updated post, here are some things to try, using the concepts described above:
\documentclass[11pt,a4paper,fleqn,draft]{article}
\usepackage{url}% http://ctan.org/pkg/url
\begin{document}
\begin{center}
{\LARGE\bf An \textit{a priori} Typology of Sentential Negation from\par an HPSG Perspective\par}
\bigskip
{\large Joshua Crowgey\par}
University of Washington
\vspace*{3\bigskipamount}
Proceedings of the HPSG 2012 Conference
\bigskip
Department of Linguistics, Chungnam National University Daejeon, South Korea
\medskip
Stefan M{\"u}ller (Editor)
\medskip
2012
\medskip
CSLI Publications
\medskip
\url{http://csli-publications.stanford.edu/}
\end{center}
\newpage
\end{document}
As David Carlisle pointed out at extrarowheight vs arraystretch, \extrarowheight is a length added by the array package to change the default inter-line gap setting between array or tabular lines. It can be positive or negative (though it appears the negative values are limited in how close they can scrunch the lines).
Here is a demonstration showing both negative and positive \extrarowheight:
\documentclass{article}
\usepackage{array}
\begin{document}
\begin {table}[ht]
\begin{center}
\setlength\extrarowheight{-3pt}
\begin{tabular}{ccc}
1 & 2 & 3\\
4 & 5 & 6\\
7 & 8 & 9\\
\end{tabular}
\caption{My caption}
\end{center}
\end{table}
\begin {table}[ht]
\begin{center}
\setlength\extrarowheight{6pt}
\begin{tabular}{ccc}
1 & 2 & 3\\
4 & 5 & 6\\
7 & 8 & 9\\
\end{tabular}
\caption{My caption}
\end{center}
\end{table}
\end{document}
Best Answer
I'd add the clauses below the main entry in the header: