[OS X TeX] Unexpected quotation marks

[Michael Kubovy]

Deat TeXers,

This file

%%!TEX TS-program = xelatexmk
%%!TEX encoding = UTF-8 Unicode
\documentclass[11pt]{article}
\usepackage{xunicode}
\usepackage[cm-default]{fontspec}
\defaultfontfeatures{Mapping=tex-text}
\setmainfont{Palatino}

\title{Article}
\author{Author}
\date{}

\begin{document}
\maketitle

should be ``quoted''

\end{document}

does not produce raised inverted commas at the beginning of the text  
and raised commas at the end. Instead it produces pairs of slanted  
apostrophes at both ends. Is this characteristic of Palatino, or am I  
missing something in the preamble?
_____________________________
Professor Michael Kubovy
University of Virginia
Department of Psychology
USPS:     P.O.Box 400400    Charlottesville, VA 22904-4400
Parcels:    Room 102        Gilmer Hall
         McCormick Road    Charlottesville, VA 22903
Office:    B011    +1-434-982-4729
Lab:        B019    +1-434-982-4751
Fax:        +1-434-982-4766
WWW:    http://www.people.virginia.edu/~mk9y/



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