\title{
On Psycholinguistic Grammars
}

\author{Patrick Juola
\thanks{Patrick Juola is a researcher at the Department of Experimental
Psychology, Oxford University.  He received his Ph.D. in 1995 from the
University of Colorado.  His research interests include computational
psycholinguistics and information theory.} \\
University of Oxford \\
{\tt patrick.juola@psy.ox.ac.uk } \\ \\
}


\begin{abstract}
It has long been known that language acquisition is only possible
if information is available above and beyond the mere presence of a
set of strings in the language.  One commonly postulated source of
such information is a (possibly innate) constraint on the syntactic
forms that a grammar can take.  This paper develops and presents a
set of formalisms based on the
Marker Hypothesis, that natural languages are ``marked'' for complex
syntactic structure at surface form.  It further compares the expressivity
and restrictedness of these formalisms and
shows that, first, not all constraints are actually restrictive, and
second, that the Marker Hypothesis, and its implicit function/content
word distinction, provide strong restrictions on the
form of allowable grammars. These restrictions may in turn provide evidence
about its
actual psychological reality and salience.
In particular, the class of strongly marked languages can be
demonstrated to {\em not} admit all finite languages and thus
not be subject to the hangman's noose of Gold's learnability proofs, and
it is conjectured that these languages may provide
a computable method of inferring human-like languages.
\end{abstract}