// Load as much data as possible, as a result frame rate will drop.
// Good for fast loading when showing progress bars.
Application.backgroundLoadingPriority = ThreadPriority.High;

// Load data very slowly and try not to affect performance of the game.
// Good for loading in the background while the game is playing.
Application.backgroundLoadingPriority = ThreadPriority.Low;

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    void Example() {
        Application.backgroundLoadingPriority = ThreadPriority.High;
        Application.backgroundLoadingPriority = ThreadPriority.Low;
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    def Example():
        Application.backgroundLoadingPriority = ThreadPriority.High
        Application.backgroundLoadingPriority = ThreadPriority.Low