How to get the current value of a select box?

Here is my code:

<input type="text" id="search_form" name="search" />
<%= observe_field 'search_form',
                 :frequency => 0.5,
                 :update => 'results',
                 :url => { :controller => 'programs', :action=>
'get_results',
                 :search_type => select_type }, # an error occurs
                 :with => "'search_text=' + escape(value)"%>
<%= select "select","type",{"BOY" => '1', "Girl" => '2'}%>

Can anyone tell me how to pass the value of the select box when i call
"get_results"?