received_notes not working

gistfile1.txt

class User < ActiveRecord::Base  

  has_many :notes, foreign_key: "sender_id", dependent: :destroy
  has_many :outgoing_notes, through: :notes, source: :user_recipient
  has_many :incoming_notes, as: :receivable ,
                            class_name: "Note",
                            dependent: :destroy
  has_many :received_notes, through: :incoming_notes, source: :sender
end


class Note < ActiveRecord::Base
  attr_accessible :description, :sender_id, :receivable_id, :receivable_type

  belongs_to :sender, class_name: "User"
  belongs_to :receivable, polymorphic: true
end

User Show Page:

<%= form_tag('/notes', method: :post) do %>

  <%= label_tag  :description, "Post a Note:" %>
  <%= text_field_tag :description %>
  <%= hidden_field_tag :sender_id, @current_user.id %>
  <%= hidden_field_tag :receivable_id, @user.id %>
  <%= hidden_field_tag :receivable_type, 'user' %>

  <%= submit_tag "Post" %>

<% end %>

<%= @user.received_notes %>