I've been told that it helps to have your sound turned on. The jury is still out on that one as far as I'm concerned. It might be annoying to coworkers if you are at work. See below:
Subject: FW: male vs. female test
There are 5 noticeable changes between the 2 photos. Women on average can spot 4 of 5 within 30 seconds. It generally takes men up to 1 minute to find 3. How many can you find in one minute?
(It's a German test, so don't mind the foreign title.)
I had to look very hard.