trigger trouble -- procedure not found

I'm having trouble creating a trigger.  First i'm creating a function,
add_to_search in PL/pgSQL.

\df verifies the existance of this function:smallint                 | add_to_search       | text, text, text, integer

but when I call:

CREATE TRIGGER item_insert_search_add AFTER INSERT   ON item FOR EACH ROW   EXECUTE PROCEDURE add_to_search (name,
description,reason, node_id);
 

I get: 
ERROR:  CreateTrigger: function add_to_search() does not exist

What am I missing here?  It seems to me that I'm missing something very
simple, but I can't figure out what it is for the life of me.

Kevin Way