This begs for a little more explanation...

ruby_koans_message_passing.rb

def test_methods_can_be_invoked_by_sending_the_message
  mc = MessageCatcher.new

  assert mc.send(:caught?)   #Note: so this is the same as mc.caught?
end

def test_methods_can_be_invoked_more_dynamically   #Note: or it shoudl say, calling a method is the same as sending a message to the class object.
  mc = MessageCatcher.new

  assert mc.send("caught?")
  assert mc.send("caught" + ? )    # What do you need to add to the first string?
  assert mc.send("CAUGHT?".____ )      # What would you need to do to the string?
end

def test_send_with_underscores_will_also_send_messages
  mc = MessageCatcher.new

  assert_equal __, mc.__send__(:caught?)

  # THINK ABOUT IT:
  #
  # Why does Ruby provide both send and __send__ ?
end