title: What's the minimum lag detectable by a human?
body: <blockquote>
    <p><strong>Possible Duplicate:</strong><br>
    <a href="https://stackoverflow.com/questions/536300/what-is-the-shortest-perceivable-application-response-delay">What is the shortest perceivable application response delay?</a>  </p>
  </blockquote>
  
  
  
  <p>I've been profiling some JavaScript UI code because it feels a little laggy. So far, I've found some bottlenecks and optimized them out, but I'd like to define a measurable requirement for this.</p>
  
  <p>How quickly should a response occur in order for a human not to notice lag? For example, what's the minimum detectable delay between when a keyboard key is pressed and when a letter appears on the screen? At what point is further optimization not going to make any difference to a human?</p>
  
  <p>A lot of monitors have a refresh rate at about in the 60-120Hz range. Does that mean the magic number is around 8-16ms?</p>