If you design the agents to have memory, they can know things about their environment. They remember where they've been on the board, and what happened there. They can go back to certain places, with certain expectations. Eventually, programmers say the agents have beliefs about their environment, and that they are acting on those beliefs. That's not literally true, of course, but it might as well be true. It looks that way.
But what's interesting is that over time, some agents develop mistaken beliefs. Whether from a motivation conflict, or some other reason, they start acting inappropriately. The environment has changed but they don't seem to know it. They repeat outmoded patterns. Their behavior no longer reflects the reality of the chessboard. It's as if they're stuck in the past. In evolutionary programs, those agents get killed off. They have no children. In other multi-agent programs, they just get bypassed, pushed to the periphery while the main thrust of agents moves on. Some programs have a "grim reaper" module that sifts them out from time to time, and pulls them off the board.
But the point is, they're stuck in their own past. Sometimes they pull themselves together, and get back on track. Sometimes they don't.
Thoughts like these made me very uneasy. I shifted in my chair, glanced at the clock. With a sense of relief, I saw it was time to go pick up the kids.
Eric did his homework in the car while we waited for Nicole to finish her play rehearsal. She came out in a bad mood; she had thought she was in line for a lead role, but instead the drama teacher had cast her in the chorus. "Only two lines!" she said, slamming the car door. "You want to know what I say? I say, 'Look, here comes John now.' And in the second act, I say, 'That sounds pretty serious.' Two lines!" She sat back and closed her eyes. "I don't understand what Mr. Blakey's problem is!"
"Maybe he thinks you suck," Eric said.
"Rat turd!" She smacked him on the head. "Monkey butt!"
"That's enough," I said, as I started the car. "Seat belts."
"Little stink-brain dimrod, he doesn't know anything," Nicole said, buckling her belt.
"I said, that's enough."
"I know that you stink," Eric said. "Pee-yew."
"That's enough, Eric."
"Yeah, Eric, listen to your father, and shut up."
"Nicole…" I shot her a glance in the rearview mirror.
"Sor-ry."
She looked on the verge of tears. I said to her, "Honey, I'm really sorry you didn't get the part you wanted. I know you wanted it badly, and it must be very disappointing."
"No. I don't care."
"Well, I'm sorry."
"Really, Dad, I don't care. It's in the past. I'm moving on." And then a moment later, "You know who got it? That little suckup Katie Richards! Mr. Blakey is just a dick!" And before I could say anything, she burst into tears, sobbing loudly and histrionically. Eric looked over at me, and rolled his eyes.
I drove home, making a mental note to speak to Nicole about her language after dinner, when she had calmed down.
I was chopping green beans so they would fit in the steamer when Eric came and stood in the kitchen doorway. "Hey Dad, where's my MP3?"
"I have no idea." I could never get used to the idea that I was supposed to know where every one of their personal possessions was. Eric's Game Boy, his baseball glove, Nicole's tank tops, her bracelet…
"Well, I can't find it." Eric remained standing in the doorway, not coming any closer, in case I made him help set the table.
"Have you looked?"
"Everywhere, Dad."
"Uh-huh. You looked in your room?"
"All over."
"Family room?"
"Everywhere."
"In the car? Maybe you left it in the car."
"I didn't, Dad."
"You leave it in your locker at school?"
"We don't have lockers, we have cubbies."
"You look in the pockets of your jacket?"
"Dad. Come on. I did all that. I need it."
"Since you've already looked everywhere, I won't be able to find it either, will I?"
"Dad. Would you please just help me?"
The pot roast had another half hour to go. I put down the knife and went into Eric's room. I looked in all the usual places, the back of his closet where clothes were kicked into a heap (I would have to talk to Maria about that), under the bed, behind the bed table, in the bottom drawer in the bathroom, and under the piles of stuff on his desk. Eric was right. It wasn't in his room. We headed toward the family room. I glanced in at the baby's room as I passed by. And I saw it immediately. It was on the shelf beside the changing table, right alongside the tubes of baby ointment. Eric grabbed it. "Hey, thanks Dad!" And he scampered off. There was no point in asking why it was in the baby's room. I went back to the kitchen and resumed chopping my green beans. Almost immediately:
"Daa-ad!"
"What?" I called.
"It doesn't work!"
"Don't shout."
He came back to the kitchen, looking sulky. "She broke it."
"Who broke it?"
"Amanda. She drooled on it or something, and she broke it. It's not fair."
"You check the battery?"
He gave me a pitying look. " 'Course, Dad. I told you, she broke it! It's not fair!"
I doubted his MP3 player was broken. These things were solid-state devices, no moving parts. And it was too large for the baby to handle. I dumped the green beans on the steamer tray, and held out my hand. "Give it to me."
We went into the garage and I got out my toolbox. Eric watched my every move. I had a full set of the small tools you need for computers and electronic devices. I worked quickly. Four Phillips head screws, and the back cover came off in my hand. I found myself staring at the green circuit board. It was covered by a fine layer of grayish dust, like lint from a clothes dryer, that obscured all the electronic components. I suspected that Eric had slid into home plate with this thing in his pocket. That was probably why it didn't work. But I looked along the edge of the plastic and saw a rubber gasket where the back fitted against the device. They'd made this thing airtight… as they should.
I blew the dust away, so I could see better. I was hoping to see a loose battery connection, or a memory chip that had popped up from heat, anyway something that would be easy to fix. I squinted at the chips, trying to read the writing. The writing on one chip was obscured, because there seemed to be some kind ofI paused.
"What is it?" Eric said, watching me.
"Hand me that magnifying glass."
Eric gave me a big glass, and I swung my high-intensity lamp low, and bent over the chip, examining it closely. The reason I couldn't read the writing was that the surface of the chip had been corroded. The whole chip was etched in rivulets, a miniature river delta. I understood now where the dust had come from. It was the disintegrated remains of the chip. "Can you fix it, Dad?" Eric said. "Can you?"
What could have caused this? The rest of the motherboard seemed fine. The controller chip was untouched. Only the memory chip was damaged. I wasn't a hardware guy, but I knew enough to do basic computer repairs. I could install hard drives, add memory, things like that. I'd handled memory chips before, and I'd never seen anything like this. All I could think was that it was a faulty chip. These MP3 players were probably built with the cheapest components available.
"Dad? Can you fix it?"
"No," I said. "It needs another chip. I'll get you one tomorrow."
" 'Cause she slimed it, right?"
"No. I think it's just a faulty chip."
"Dad. It was fine for a whole year. She slimed it. It's not fair!" As if on cue, the baby started crying. I left the MP3 player on the garage table, and went back inside the house. I looked at my watch. I would just have time to change Amanda's diaper, and mix her cereal for dinner, before the pot roast came out.