self centered

So I'm working on this Rails project where I am creating a model object with associations all-at-once using a technique recommended by Mr Josh Susser.

The relevant part of my code looks like this:

def recipient_list=(recipient_emails)
  puts "Assigning recipient list: #{recipient_emails}"
  if new_record?
    @recipient_list = recipient_emails
  else
    create_recipients(recipient_emails)
  end
end

def after_create
  self.recipient_list = @recipient_list if @recipient_list
end

Originally this wasn't invoking the recipient_list= method during after_create
because I had removed the "self." thinking it was superfluous. Adding it back in
resulted in the desired behavior. But why?

Best I can figure is that the following looks like a local variable assignment to Ruby:

  recipient_list = @recipient_list if @recipient_list

Whereas the following is a method invocation:

  self.recipient_list = @recipient_list if @recipient_list