The gap between what computers can do and what humans can do is shrinking.

This course explores one advance that has fueled this trend: a computational model called an artificial neural network. Artificial neural networks are one approach to creating artificial intelligence — programs that imitate the cognitive functions of humans.

In this lesson, we’ll peer inside a few simple neural nets to probe how they work, and then we’ll explore a much bigger neural net to appreciate what they can do.

The brain contains more than 80 billion cells — called neurons — which exchange information with one another via small pulses of electricity.

One neuron doesn’t talk directly with all 80 billion others. Rather, they are connected into structures that perform specialized functions. These structures are biological neural networks.

The human brain is too complex to discuss in much detail here, but we don’t need to know all the details to land on its most important characteristic — “Brains learn from experience.”

Each time you learn a new game, a dance, or a mathematical skill, neurons in your brain strengthen their lines of communication with some neurons and prune their connections to others.

The structure of a neural network evolves as you gain new abilities.

Artificial neural networks — ANNs, for short — were invented in order to understand and emulate the functions of the mammalian brain.

But, in recent years, they have taken on a life of their own.

Computers today can follow billions of individual instructions each second. This explosion in computing power has let scientists build ANNs that learn to identify people in images, play chess, and even help doctors make medical diagnoses.

In other words, ANNs learn to do complex tasks that previously only humans could do.

At the end of this lesson, you’ll have an opportunity to play with an ANN that we’ve taught to see, but it will make more sense to get acquainted with the basics of how ANNs work first.

Artificial Neurons

Just as biological neurons are the basic units of the brain, artificial neurons are the computational building blocks of an artificial neural network (ANN).

And, like biological neurons, artificial neurons respond to the information that’s presented to them.