Software decides things for you all day: what appears at the top of a feed, whether a photo has your face in it, what word you meant when you mistyped. The part of a program that decides is called an AI model.
Today you will
- meet the main kinds of AI model
- build one yourself in Scratch: a guesser made of rules that tells a cat from a dog
- find where it works and where it falls apart, which is the problem you solve next lesson
Here are five real things software does. Your teacher will take them one at a time. For each one, call out the kind of model you think is behind it.
Choose from these four kinds of model:
- Generative: it makes something new, such as text, a picture or code.
- Recommendation: it picks what to show you next, from what you liked or watched before.
- Classifier: it sorts something into a group, such as cat or dog, or spam or not spam.
- Agent: it is given a goal and works through the steps to reach it on its own.
- It recommends the next video you should watch.
- It turns a sentence you typed into a picture.
- It finishes the line of code you started.
- It spots a face in a photo.
- It books a table at a restaurant for you, on its own.
| Kind | What it does | Where you meet it when coding |
|---|---|---|
| Generative | Produces something new: text, an image, code | An assistant that drafts a function or explains code |
| Recommendation | Ranks options for one person | What a shop or a feed shows a given user |
| Classifier | Sorts an input into categories | Cat or dog, spam or not, rock or paper |
| Agent | Takes a goal, plans, uses tools, acts in a loop | Software that carries out a multi-step task |
The one you are about to build is a classifier. It takes something in and puts a label on it, and it is the simplest of the four to build by hand.
Go to scratch.mit.edu and click Create to start a new project. Call it Cat or Dog. If you are not signed in, the editor has no box for the name, so you will name it when you save it to your computer at the end.
You will write all of today's code on the cat sprite that is already there, so you do not need to add anything.
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Scratch is developed by the Lifelong Kindergarten Group at the MIT Media Lab. It is available for free at https://scratch.mit.edu