Converting asmx web-service to WCF web-service - why does the JSON parameter need additional quotation marks?

I have a asmx web-service that returns a list of countries for a continent. When using JQuery to call the web-service I use:

$.ajax({
            type: "POST",
            contentType: "application/json; charset=utf-8",
            url: "InternationalLookup.asmx/LoadCountries",
            data: '{ continentName: "' + $(this).val() + '" }',
            dataType: "json",
            success: function (response) {
                //..code
            },
            error: function (response) {
                //..code
            }
        });

This works fine with the asmx code but when using the WCF service I have to change it to:

$.ajax({
            type: "POST",
            contentType: "application/json; charset=utf-8",
            url: "InternationalLookup.svc/LoadCountries",
            **data: '{ \"continentName\": "' + $(this).val() + '" }',**
            dataType: "json",
            success: function (response) {
                //..code
            },
            error: function (response) {
                //..code
            }
        });

Note the difference in the data I have to pass in, it now requires additional quotation marks around the continent name. My WCF service and it's configuration:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <system.serviceModel>
<behaviors>
  <serviceBehaviors>
    <behavior name="InternationalLookupBehavior">
      <serviceMetadata httpGetEnabled="true" />
      <serviceDebug includeExceptionDetailInFaults="true" />
    </behavior>
  </serviceBehaviors>
  <endpointBehaviors>
    <behavior name="InternationalLookup">
      <enableWebScript />
    </behavior>
  </endpointBehaviors>
</behaviors>
<services>
  <service behaviorConfiguration="InternationalLookupBehavior"
      name="USQ.Websi开发者_StackOverflow社区tes.RefreshLayout.Webservices.UsqInternationalLookup">
    <endpoint address="" binding="wsHttpBinding" contract="IInternationalLookup">
      <identity>
        <dns value="localhost" />
      </identity>
    </endpoint>
    <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange" />
  </service>
</services>

[ServiceContract]
public interface IInternationalLookup
{
    [OperationContract]
    [WebInvoke(Method = "POST", RequestFormat = WebMessageFormat.Json, ResponseFormat = WebMessageFormat.Json)]
    string LoadCountries(string continentName);
}

Despite having quite some troubles getting it to work I would like to know why the parameter for the WCF web-service has to be wrapped in additional quotation marks.

The JSON specification states that object member names must be enclosed by double quotes - see www.json.org - so this is what WCF enforces. I don't know why the JSON parser used by ASMX services chose to be more lax in enforcing the syntax.