<code>"fd"</code> for forward differences, and <code>cd</code>
            for central difference; default is <code>"fd"</code>.</p></dd>

        <dt>nAGQ</dt>
<dd><p>numeric scalar denoting the number of quadrature points; default is
            11 when the number of random effects is one or two, and 7 otherwise.</p></dd>

        <dt>update_GH_every</dt>
<dd><p>numeric scalar denoting every how many iterations to
            update the quadrature points during the EM-phase; default is 10.</p></dd>

     