First attempt to adding states to a custom Content type

// sample code
/**
 * Implementation of hook_form_FORM_ID_alter()
 */
function demo_form_sport_node_form_alter(&$form, &$form_state, $form_id) {
    $form['field_winter_sports'] = array(
    '#states' => array(
        'visible' => array(   // action to take.
            ':input[name=field_season]' => array('value' => t('winter')),
        ),
    ),
);
}

i am trying to alter a form from a "sport" node type. my "sport" node type has 2 fields.

field_season List (text) Check boxes/radio buttons
field_winter_sports List (text) Check boxes/radio buttons
there are two options in field_season, summer or winter.

if someone selects winter in field_season, i want to make field_winter_sports visible, otherwise remain hidden.

with my current code, when i select winter right now, nothing happens.