/**
 * Contributor only see his/her own post
 */
function posts_for_current_author($query) {
    global $pagenow;
 
    if( 'edit.php' != $pagenow || !$query->is_admin )
        return $query;
 
    if( !current_user_can( 'edit_others_posts' ) ) {
        global $user_ID;
        $query->set('author', $user_ID );
    }
    return $query;
}
add_filter('pre_get_posts', 'posts_for_current_author');