actually Peter Falk (and Gena Rowlands) didn't like to improvise. Cassavetes made them better actors. They worked with the confines of the script, but wanted the actor to do the rest, to find the character, to be the character.

I don't know if it is a dig but John liked his actors to improvise (which may speak to why Falk was so good in his movies). Ricardo did not improvise but preferred direction, which may be a result of English being a second language. John May have found that Ricardo was not quite at ease with improvisation.