I think that if you're good at maths you'll be able to help me without having heard of this before, assuming you know about classical conditioning it's explained here; http://brembs.net/classical/suppress.html The measure of the extent to which the CS suppresses responding is called the suppression ratio and is normally defined as being the rate of responding in the presence of the CS divided by the sum of the response rate in the presence of the CS and in the absence of the CS. If A is the response rate during CS and B is the response rate in the absence of the CS (usually measured immediately prior to CS presentation) then the suppression ratio is A/(A+B). With this formula a CS which completely suppresses responding will score 0.0, one that has no particular effect will score 0.5, a stimulus which elevates responding for some reason will score between 0.5 and 1.0. It just seems to me like they just randomly figured.. okay let's just multiply or divide or whatever until we get the numbers we want. I don't see why you would add how often the rat presses the lever without a shock to how often he presses it with the shock and then divide that by how often he presses it without the shock.. Let's say I am the one being conditioned and I make the response 583 times in 10 seconds normally, then you shock me for 10 seconds and I do it 80 times.. 583/(583+80) = 1.1... That's would mean that it had increased the number of times I pressed responded.. What on earth.. I am definately completely misunderstanding this somewhere along the way... help?