The Four Types of Artificial Intelligence

Reactive, Limited Memory, Theory of Mind, and Self-Aware: What to know about the different levels of AI and how they compare to one another

Artificial Intelligence, or AI, is increasingly becoming a part of our everyday lives, even if we don't always know it. Because it's already here and only going to become more critical in the future, it's essential to understand the four types of artificial intelligence, how they're distinct, and which ones are in use today.

Overview of Artificial Intelligence

Artificial Intelligence is measured in comparison to the functions of the human mind. A true, fully complete AI could replicate—and likely extend—a human brain's functions.

It would be self-aware, have consciousness and memories, could learn and make predictions about likely future events—and would do these things on its own, without human intervention or input from programmers.

The Four Types of AI: Reactive Machines

The first and most basic kind of AI is Reactive Machines. These machines have intelligence that exists almost entirely in the present moment (eat your hearts out, meditators!). Programmers build Reactive Machines around complex sets of rules. In addition to those rules, they may include neural networks that allow them to learn and adapt in the moment.

Crucially, though, this type of AI can't form memories or act based on past experiences. Because they can't create memories, they can't take past occurrences, even those that happened to them, and use them to make new decisions.

In this way, they're restricted to the scenarios and information covered in their sets of rules. Because of this limitation, one can trick Reactive Machines into being defeated by forcing them to operate outside their limited set of rules.

Reactive Machines also don't have a concept of the future. They can use their rules to make extrapolations about what might come next, but only within the boundaries established by their rule sets.

Because they can't change their future actions based on past occurrences, Reactive Machines can't learn.

The Four Types of AI: Limited Memory

This more-advanced AI type has the abilities of reactive machines but adds a concept of the past. While Limited Memory AIs aren't forming memories, they are aware of a recent past and can use the data captured at that time to influence their decisions.

Self-driving cars are the best example here. They continuously monitor the conditions around them—what other vehicles are doing, where objects are, how pedestrians are moving, etc.—and holding that information in a temporary state to influence their actions.

As you might imagine, Limited Memory AIs process tremendous amounts of data and make decisions very quickly.

This AI level is called "Limited Memory" because these past experiences aren't stored permanently, and it can't use them for all future learning. Instead, these past experiences are saved for a short time while they're practical and then discarded.

  • Examples: Self-driving cars

The Four Types of AI: Theory of Mind

With Theory of Mind AI, we get closer to the science-fiction ideal of artificial intelligence. This level of AI includes all of the aspects of Reactive Machines and Limited Memory. But it adds a crucial and complex bit of understanding: that the living objects (people, animals, etc.) around them have a thing called a "mind."

Once an AI understands that other creatures have minds, it can then understand that it should learn and adjust its decisions based on those minds. It then understands minds generate thoughts and emotions (even if it doesn't truly understand what those things are yet) and that thoughts and emotions will influence behavior. The AI has to use those factors in its decision-making framework.

  • Examples: There are no known examples of Theory of Mind AI in existence (though some robots that attempt to understand and simulate point a direction for this type)

The Four Types of AI: Self Aware

Self-Aware AI is the final and most complex, and mature level of AI. It's a genuinely self-aware intelligence. Any AI from science fiction falls into this category. It's an entity with true consciousness.

It's aware of its existence and its internal states (and potentially emotions), can form memories of the past, and make predictions. It's aware of other consciousnesses and can take them into account when making decisions. Crucially, it can learn and become more intelligent based on its experiences.

A Self-Aware AI would require extremely flexible programming logic, an ability to update its logic on its own, and a tolerance for inconsistency since human behavior isn't always neatly predictable or rigidly patterned.

  • Examples: Self Aware AI doesn't exist currently and is likely many years away from being achieved

The Four Types of AI Compared

The four key types of AI, and their key characteristics, are listed below for easy reference and comparison.

AI Type Follows
Can Learn  Has Memories Knows Other Minds Exist  Aware of Emotion   True AI
Reactive Machines  ✓          
Limited Memory ✓  ✓   limited      
Theory of Mind   ✓  ✓  ✓  ✓  ✓  
Self Aware  ✓  ✓  ✓  ✓ ✓   ✓

Should We Worry About AI?

Anyone passing familiar with science fiction about AIs knows that things often go wrong for humans once a machine achieves consciousness (hello, Skynet). So, should we be worried about AI?

There's no single answer to this question, but it's a good idea to be thoughtful and careful about how we go about creating and using fully self-aware AI.

There's the doomsday scenario of AIs replacing humans—whether that means taking human jobs and leaving people without work or income or the darker Terminator-style storyline. There are also ethical concerns: Is it acceptable to create a consciousness that can think and feel and then force it to do our bidding?

Some ethicists study AI and write about these questions. As AI becomes more advanced and more widespread, we'll need to make sure we listen to them, and our laws and governments adapt to the unique challenges—and possibilities—created by AI.

  • When was artificial intelligence invented?

    The term “artificial intelligence” originates from a 1956 conference at Dartmouth College in New Hampshire. However, the earliest AI program was created by Christopher Strachey in 1951 at the University of Oxford.

  • What is artificial general intelligence?

    Artificial general intelligence, or AGI, is the ability of a computer program to perform any intellectual task that can be performed by a human. Artificial intelligence is usually limited to more narrow tasks.

  • How will artificial intelligence change the future of education?

    Artificial intelligence is already used in education to monitor student and teacher performance. AI-focused education modules are being developed that personalize lessons to students' learning styles.

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