Keyboard down arrow with typeahead

In typeahead in Jquery, how do I make the search suggestion just only selected down ?

$(document).ready(function () {
        $('#search').typeahead({
            source: function (query, result) {
                $.ajax({
                    url: "server.php",
                    data: 'query=' + query,            
                    dataType: "json",
                    type: "POST",
                    success: function (data) {
                        result($.map(data, function (item) {
                            return item;
                        }));
                    }
                });
            }
        });