Daily Archives: April 17, 2008

Grilled cheese and the science of successive approximation

Were you paying attention in those psychology classes?

Do you remember the experiments where a rat was trained to press a lever to get food?

It’s amazing how relevant experiments on rats can be to parenting.

In pursuing my psychology degree, I took a lab where I had to perform that experiment myself. I had a rat of my own, which I named – very appropriately, I thought – Rat (hey, if it’s good enough for George of the Jungle, it’s good enough for me).

The first goal of the experiment was to get the rat to understand that pressing a lever meant getting food. There were other goals once that was accomplished, but let’s focus on that goal for now.

Rat was just not getting it. Either that, or he was just really, really stubborn. I spent many nights in that lab until well after midnight faithfully recording him doing nothing of interest (which eventually translated into a graph that crossed enough pages of graph paper to run the length of our dormitory hallway). Eventually, however, he started to get the picture. When he made a move toward the lever, I dropped him a food pellet. If he moved a little closer, he got another pellet. Brushed against the lever? Another pellet. Touched it intentionally? Another pellet. Pressed it completely? More pellets. This process took a long time – but when it worked, it worked. Eventually, getting him to stop pressing the lever (phase 2 of the experiment) was even harder.

That process of rewarding Rat for each progressive step closer to the goal is called “successive approximation.” At first, he didn’t have to press the lever to get food, he just had to look at the lever. Once he got that, he had to make progress toward the larger goal before he’d get his food. Looking at it was no longer enough. He had to move close to it. Eventually, he’s feeding himself by pressing the lever. This teaching method, it has been proven time and time again, works.

Flash-forward almost 20 years. I don’t think about Rat often. But I did today.

My three-year-old daughter has become a very picky eater. It’s gotten to the point that it’s commonplace for my wife to make two different dinners every night – one for “Little Mommy” and one for the rest of us. Last week we decided that would stop. Little Mommy was going to learn to eat what we gave her.

It didn’t go so well for the first 4 days. We had a complete meltdown just getting the compromised 1/8″ square piece of grilled cheese near her mouth. Much drama ensued at that meal. Food flew; screams were loosed. The next day we were visiting friends and despite some earnest attempts at cajoling on all of our parts, no progress was made by us parents (she succeeded in manipulating us, however, which was a setback). The following day we were back at it, though there was much less drama. Finally, today, at lunch, Rat came to mind.

Oddly, it was grilled cheese again. This time, instead of reducing the size of the task, my wife tried something different. She put some soy-butter, Little Mommy’s favorite – on a small part of the top of the sandwich. While that was promptly licked off, I decided to start eating crackers I knew Little Mommy liked. When she asked for one, I said “Sure. Just lick the sandwich – but not on the soy-butter part.” After some whining, she did it, and I gave her a cracker. The next step was to get her to eat just a bite of the sandwich to get another cracker. She couldn’t have gotten a smaller bite if she used a laser scalpel, but she did take a bite, so she got another cracker.

Now we’re at the breaking point. Lots of accolades went along with that last cracker. She’s all proud of herself. Now we push. “Okay, if you take four bites, you can have another cracker.” She likes counting, too, so we all counted the bites, which – without any prompting – got bigger, and bigger, until bite number 4 was actually too much to have in her mouth at once. But as I gave her the cracker, I knew we had finally prevailed. She herself suggested the next goal would be five bites, which she attacked with gusto. With almost nothing left to the sandwich, and praises all around, she had finally eaten the same lunch as everyone else.

I guarantee that without using that successive approximation of licking, to infinitesimally small bites, to larger bites, we’d still have no progress.

Have we won the war? Nope. We’ll probably be able to get her to eat grilled cheese again with minimal effort, but I’m sure that any other “new” food she tries will take at least some degree of that same process.  But we now have a strategy that works. After 4 days of failure with alternate strategies (yelling, bribing, punishing, & others), I’m thrilled to be making progress.