So let's say, the fixed ratio is every other time you get the reward; that would mean you get a reward the first time, the third time, the fifth time, the seventh time, the ninth time, and so forth. That's a fixed ration reward. The third category is a Fixed Interval reward, and here the reward is fixed not based on the amount that the person engaged in the activity, but based on time. So let's say, the fixed interval said the reward comes every three units of time. We look here, one, two, three. That means the reward comes right here. The reward then comes one, two, three units later. One, two, three units after that. One, two, three units after that. So you see here, sometimes, as in this case right here. The reward hit right on a time when the user was engaging in the action. But some other times it didn't. Here the reward was given right here. And the action was much earlier. That's the point of the Fixed Interval reward. It's based on time, not based on what the user does. But it's still fixed in some way. It's still a regular pattern when the reward happens. And then, the final category of rewards are Variable rewards. The reward is on no fix schedule. And essentially, when we think about the gamification this first one here, the Continuous reward is really of the least interest. The idea that you'll get a reward every time, tends to not feel like a reward. It make sense, at some point that's not going to motivate people when it's just something automatic. It's not really a reward band, it's just noticing as your plan. The kind of fixed rewards, ratio and interval have some psychological value. But, as we'll see the brain picks up onthe pattern. And that tends to ultimately dull the psychologicalimpact of the reward although, it makes those things easier to do in gamification because those are the classic examples of badges and questions so forth. Where there's some defined set of processes or some defined set of time as we saw on Samsung Nation, that then unlocks the reward. The final one is probably the most interesting, this is the Variable reward. And as I said, our brains love surprises. This probably comes from evolution. Our brains are evolved basically to be hunter-gatherer species. And surprise. Something that's different, unexpected out of place with the terrain is really interesting. And it's really interesting partly because, if you're a neolithic hunter gatherer it might be something like a big wild animal that's going to eat you. So, our brains are really good at picking out, for example, movement on a solid field. And our brains are really good at encouraging us to take a closer look at things that are somehow different, and something that is not according to a pattern. Something that seems to come up randomly, fits into that category of surprise So just based on the way our brains have been evolved, we tend to respond powerfully to unexpected and to variable schedule rewards. So then let's look at some examples of gamification rewards and how they fit on this structure. The Samsung Nation hang out quest that I showed you, the one that was completion contingent expected reward is also a fixed interval reward because it's about time. It's about a certain amount of time that has to pass before you get the reward and so we call that Fixed Interval. What about this one? Here's another quest that you can go on, on Samsung Nation. And this one is based not on time, but the number of visits that you make to the site. You have to visit the site so many times to unlock this badge. What category does that fit under? That badge in Samsung Nation is a fixed ratio badge, because it happens every certain number of times. That you go to the site as opposed to being based on time.