What is a Rational Agent? The Concept of Rationality - Explained

Rationality

'Rationality' is the most important concept in understanding Artificial Intelligence (If you haven't already read, take a quick look at What is Artificial Intelligence?).

To better understand AI, we can compare it with Humans. This leads us to the below four categories.

Among these possibilities, a system/agent that can act rationally is good. On a high level, we define being rational as doing the right thing. But, is it always possible to do the right thing? And, what does it mean to do the right thing?

For easier understanding, let's compare with humans. Is it always possible for us to do the right thing? Even though we aim to do the right thing with the knowledge we have acquired so far, we cannot guarantee the result. We learn from the outcome and consider it next time we do something similar.

Similarly, acting rationally is trying to do the right thing based on the information that a system/agent has.

Agent

We would be using the word Agent quite frequently, so let's try to understand what an Agent is. An agent is something that can understand its environment (maybe via sensors or some other input devices) and act accordingly using actuators. To make it simpler, humans have eyes, ears, and other sense organs as sensors, and hands, legs, and vocal tracts as actuators.

These sensors and actuators (say, input and output devices) may vary based on the type of agent, i.e., Robotic agent or Software agent, etc.

Let's consider an example of a robot vacuum cleaner to understand this better. Assuming the vacuum cleaner has a sensor that detects dust in a specific room and an actuator that can suck the dust to clean the room.

If we assume the vacuum cleaner is a rational agent, which we have defined as doing the right thing, what is a robotic vacuum cleaner supposed to do? To keep the rooms clean. This can be done by having the vacuum cleaner clean one room, then move on to the next room and clean that room. Do we consider this rational if this process continues repeatedly? Maybe not, because this consumes electricity and the vacuum cleaner is always ON, which could be an inconvenience.

Performance Measure

So, we would need a kind of performance measure to define the agent's efficiency. How do we measure the performance of an agent? How do we measure our performance, maybe in a specific game? We would reward points when we play well and maybe some penalty points when we make mistakes.

Similarly, we could give some reward points and some penalty points to the agent. For any agent, a performance measure can be defined based on the users the agent is designed for, or at least based on the designer's initial assumptions on how the agent should work.

In our example, the performance measure could be something like giving reward points for the cleanliness of each square for a specific time interval and maybe penalty points based on the total time the vacuum cleaner has run and the power it consumes.

As a general rule, it is better to design a performance measure according to what one actually wants to be achieved in the environment rather than how one thinks the agent should behave.

Conclusion

Rationality in AI is about making the best possible decision (if not the right one all the time) based on the available information, performance measures, and experiences. Designing a perfect rational agent is challenging due to uncertainties and constraints in the real world.

Call to Action

What do you think about the idea of rational agents? Do you believe AI can ever achieve true rationality, or will it always be limited by its built-in knowledge? Share your thoughts in the comments.

This blog post draws insights from the book Artificial Intelligence: A Modern Approach by Stuart Russell and Peter Norvig. Widely regarded as a foundational resource, it has been instrumental in shaping the understanding of AI concepts and their applications.