Template Constructor using function as argument [duplicate]

This question already has an answer here:

• C++'s most vexing parse again 2 answers
• Absence of compilation error when using parametrized constructor 2 answers

My question is why does boost::scoped_thread<> t{boost::thread(FactoryThread)}; in this program run the function FactoryThread and using

boost::scoped_thread<> t(boost::thread(FactoryThread));

does not run the function FactoryThread.

#include <iostream>
#include <string>
#include <vector>
#include <mutex>
#include <thread>
#include <boost/asio.hpp>
#include <boost/thread.hpp>
#include <boost/thread/scoped_thread.hpp>


void FactoryThread()
{
    std::mutex tempEncryptData;
    std::unique_lock<std::mutex> DataThread_one(tempEncryptData);

    std::cout << "\nThread started & Mutex locked" << std::endl;
}

int main(int argc, char* argv[])
{

  try
  {
        boost::scoped_thread<> t{boost::thread(FactoryThread)};
  }

  catch(std::exception& e)
  {
        std::cout << "Exception!!" <<
                e.what() << std::endl;
  }

  return 0;
}

Thank you.