   add_answer: (answer) ->
     [response_id, loc] = answer
 
-    # only add each response once
-    return if @response_ids[response_id]
+    # only add each response_id/lat/long once
+    return if @distinct_answers[answer]
 
     # get float values from string
     split = loc.split(' ')

    # setup event listener to show info window
    google.maps.event.addListener(m, 'click', => this.show_info_window(m))

    # keep track of the response id
    @response_ids[response_id] = true

    return m


    })

    # keep track of which response ids we've rendered
    @distinct_answers = {}

    # add the markers and keep expanding the bounding rectangle
    bounds = new google.maps.LatLngBounds()
