bribe vs. reward

someone once told me that a bribe is when you give the prize first and then expect the task to be done but a reward is given after the task is completed.
i reassure myself with this definition often! i think that my kids should do what they are asked without incentive or reward but, my reality is that they don't always meet my expectations.

thing 3 has long curly hair and it can get very snarly! she hates for me to brush it(she lets my friends and sister when they are watching her-but screams at me!). so recently i've caught on to her chocolate addiction and started giving her a bowl of M&M's while she sits and lets me brush her hair. it's been working! she doesn't scream at me at all-and we are learning our colors as we go over the color of each one before she eats it!

i used to be a Dr. Phil faithful. not so much anymore-still really like him and his common sense give me a break attitude but don't catch his show as often as i used to. one thing i do remember him saying with kids was that you have to learn their currency. every kid has something that matters to him and if you know what that is you can use it as reward and punishment.

thing 1 has been kind of dragging through school this year. he just has not been getting the grades on his tests that he should be. i know he knows the material but the scores aren't reflecting that. so i've gone against some of my basic beliefs with him. i've never really thought i should pay my kids for their grades. i know a lot of parents do this and that is fine i just didn't want to do it. but my sons currency is $$$$$. so we have started to pay him for his scores. we based it off of my husbands parent's method when he was a kid.
90-100%=$1
80-89%=$0
anything below 80% he owes us $1
my husband was older when his parents used this on him and the amounts were different and it was used for end of term grades but the scale was the same. at thing 1's age i felt like he needed something more immediate than waiting for the report card. next year we can extend it to each term.

so anyway, low and behold the first 2 tests came home with 100%! which just tells me he just had no incentive!

so, am i bribing or rewarding? do you bribe or reward?