text: //Function to draw blankstimulus
  function draw_blankstimulus(canvasID,colour)
  {
  	var stimCanvas = document.getElementById(canvasID);
    var stimContext = stimCanvas.getContext("2d");
  
  	//create black stimulus box
  	var squareWidth = 250;
  	var sqystartpoint = (stimCanvas.height - squareWidth)/2;
  	var sqxstartpoint = (stimCanvas.width - squareWidth)/2;
  
  	stimContext.fillStyle = colour; // grey inner square#C0C0C0
  	stimContext.fillRect(sqxstartpoint,  sqystartpoint, squareWidth, squareWidth);// Fill black square (stimulus background)
  
  	//specification
    var cellSize = 10;
  
  	var string4stimulus = stimCanvas.toDataURL();
  
  	stimContext.clearRect(0, 0, stimCanvas.width, stimCanvas.height);
  
  	return string4stimulus;
  }
  