diff --git a/lib/active_model/serializer.rb b/lib/active_model/serializer.rb
index 50ac2bbd..cee2f8d0 100644
--- a/lib/active_model/serializer.rb
+++ b/lib/active_model/serializer.rb
@@ -98,6 +98,16 @@ module ActiveModel
       end
     end
 
+    def self.include_directive_from_options(options)
+      if options[:include_directive]
+        options[:include_directive]
+      elsif options[:include]
+        JSONAPI::IncludeDirective.new(options[:include], allow_wildcard: true)
+      else
+        ActiveModelSerializers.default_include_directive
+      end
+    end
+
     attr_accessor :object, :root, :scope
 
     # `scope_name` is set as :current_user by default in the controller.
@@ -185,6 +195,39 @@ module ActiveModel
       end
     end
 
+    def serializable_hash_for_single_resource(adapter_options, options, adapter_instance)
+      cached_attributes = adapter_options[:cached_attributes] ||= {}
+      resource = cached_attributes(options[:fields], cached_attributes, adapter_instance)
+      relationships = resource_relationships(options)
+      resource.merge(relationships)
+    end
+
+    def resource_relationships(options)
+      relationships = {}
+      include_directive = options.fetch(:include_directive)
+      associations(include_directive).each do |association|
+        relationships[association.key] ||= relationship_value_for(association, options)
+      end
+
+      relationships
+    end
+
+    def relationship_value_for(association, options)
+      return association.options[:virtual_value] if association.options[:virtual_value]
+      return unless association.serializer && association.serializer.object
+
+      include_directive = options.fetch(:include_directive)
+      opts = instance_options.merge(include_directive: include_directive[association.key])
+      relationship_value = ActiveModelSerializers::Adapter::Attributes.new(association.serializer, opts).serializable_hash(options)
+
+      if association.options[:polymorphic] && relationship_value
+        polymorphic_type = association.serializer.object.class.name.underscore
+        relationship_value = { type: polymorphic_type, polymorphic_type.to_sym => relationship_value }
+      end
+
+      relationship_value
+    end
+
     protected
 
     attr_accessor :instance_options
diff --git a/lib/active_model_serializers/adapter/attributes.rb b/lib/active_model_serializers/adapter/attributes.rb
index 9a15f616..b32169db 100644
--- a/lib/active_model_serializers/adapter/attributes.rb
+++ b/lib/active_model_serializers/adapter/attributes.rb
@@ -17,18 +17,8 @@ module ActiveModelSerializers
 
       private
 
-      def include_directive_from_options(options)
-        if options[:include_directive]
-          options[:include_directive]
-        elsif options[:include]
-          JSONAPI::IncludeDirective.new(options[:include], allow_wildcard: true)
-        else
-          ActiveModelSerializers.default_include_directive
-        end
-      end
-
       def serializable_hash_for_collection(serializers, options)
-        include_directive = include_directive_from_options(instance_options)
+        include_directive = ActiveModel::Serializer.include_directive_from_options(instance_options)
         instance_options[:cached_attributes] ||= ActiveModel::Serializer.cache_read_multi(serializers, self, include_directive)
         instance_opts = instance_options.merge(include_directive: include_directive)
         serializers.map do |serializer|
@@ -37,37 +27,8 @@ module ActiveModelSerializers
       end
 
       def serializable_hash_for_single_resource(serializer, instance_options, options)
-        options[:include_directive] ||= include_directive_from_options(instance_options)
-        cached_attributes = instance_options[:cached_attributes] ||= {}
-        resource = serializer.cached_attributes(options[:fields], cached_attributes, self)
-        relationships = resource_relationships(serializer, options)
-        resource.merge(relationships)
-      end
-
-      def resource_relationships(serializer, options)
-        relationships = {}
-        include_directive = options.fetch(:include_directive)
-        serializer.associations(include_directive).each do |association|
-          relationships[association.key] ||= relationship_value_for(association, options)
-        end
-
-        relationships
-      end
-
-      def relationship_value_for(association, options)
-        return association.options[:virtual_value] if association.options[:virtual_value]
-        return unless association.serializer && association.serializer.object
-
-        include_directive = options.fetch(:include_directive)
-        opts = instance_options.merge(include_directive: include_directive[association.key])
-        relationship_value = Attributes.new(association.serializer, opts).serializable_hash(options)
-
-        if association.options[:polymorphic] && relationship_value
-          polymorphic_type = association.serializer.object.class.name.underscore
-          relationship_value = { type: polymorphic_type, polymorphic_type.to_sym => relationship_value }
-        end
-
-        relationship_value
+        options[:include_directive] ||= ActiveModel::Serializer.include_directive_from_options(instance_options)
+        serializer.serializable_hash_for_single_resource(instance_options, options, self)
       end
     end
   end