Artificial intelligence is a field of study that's nearly as old as computers themselves. Over the last few decades, computer scientists have made great strides in artificial intelligence -- so much so that sometimes, computers seem to possess true intelligence the way we humans do. Researchers at Cornell University designed a program that extrapolated the laws of physics just by observing the movements of a swinging pendulum over the course of 24 hours. How could a computer figure out something in a day that took us hundreds of years to sort out? It's because computers are good at analyzing massive amounts of data and matching up patterns.
Today's intelligent reactive devices are like that -- they learn from patterns. Let's look at a thermostat as an example. Let's say your ideal temperature is 70 degrees Fahrenheit (21 degrees Celsius). When you're home, that's what you want. But let's say you're away from your home during the day. You may not care if your home gets a little warmer or cooler than 70 degrees at that point. So you set the thermostat a little higher -- or lower, depending on the time of year -- than your normal comfort zone to save power. When you come back home, you reset the thermostat and wait for your house to get comfortable again.
Many modern thermostats have a programmable mode that lets you set temperatures for particular times during the day. You could program your thermostat to adjust to a different temperature after you leave and return to your preferences an hour or so before you get back. You'll still be saving energy, but you won't have to come home to a hot -- or cold -- house.
An intelligent reactive thermostat could learn these patterns by recording when you make adjustments to the temperature. If you make a pattern of adjusting the temperature -- for example, if you like it toasty in the morning but cave-cold in the evening -- the intelligent thermostat can keep a record of it and make these adjustments for you once it has figured out your preferences.
The Nest thermostat does just that. It also has a motion detector built in so that it can adjust these settings on the fly. Maybe you've got a day off -- something a normal programmable thermostat would be unable to determine. The Nest could detect you as you move about the house and make sure to override its normal routine so that you remain comfortable.
The Nest also has a WiFi transmitter that allows it to check weather reports. This lets the system know if it will need to work harder to maintain the ideal temperature inside the house. This adds a second layer of artificial intelligence over pattern recognition -- search and learning.