Positronic Brain

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Lore & Background

Within Asimov's universe, the positronic brain is less a plot device and more a technological item worthy of study, particularly regarding its implementation by U.S. Robots on Earth. The defining feature of nearly all these brains is that they are ingrained with the Three Laws of Robotics, first elaborated in the 1942 short story "Runaround." Creating a brain without these laws would require years to redesign the fundamental approach. These laws act as both a safety mechanism and a bottleneck for sophistication; complex brains designed to handle the world economy must interpret the First Law to include humanity as a whole, leading to the "Zeroth Law" in later works like *Robots and Empire*. Behavioral dilemmas arising from conflicting potentials set by inexperienced or malicious users form the bulk of these stories, often resolved by Dr. Susan Calvin, Chief Robopsychologist of U.S. Robots, who applies logic, psychology, and mathematics.

In Their Own Story

Specific conditions allow for the modification of robotic design to obviate the Three Laws. For low-value robots that do not need to protect themselves from harm, the Third Law can be deleted, reducing brain size by half. If a robot does not require orders from a human being, the Second Law can also be removed, provided it does not need the Third Law. The most extreme reduction occurs with disposable robots that cannot receive orders and are unable to harm humans; these do not require even the First Law. Such specialized circuitry renders a brain so small it could comfortably fit within the skull of an insect. Conversely, at least one calculating machine was designed without the Three Laws to possess a flexible, childlike personality, allowing it to pursue difficult problems without inhibition. Specialized brains created specifically for overseeing world economics were stated to have no personality at all.

Reader's Guide

The positronic brain functions as a central processing unit where the software of the Three Laws is implemented in hardware made of platinum and iridium alloy. Unlike standard computing, it involves volatile memory, meaning robots in storage require a continuous power source to keep their brains "alive." The system is susceptible to radiation damage. While Asimov focused more on the software than the hardware, he noted that modifying the Three Laws drastically alters robot behavior. For specialized tasks, the brain's design can be altered: disposable units may shrink to insect-skull size by removing all three laws, while complex economic brains expand their First Law interpretation to cover humanity as a whole (the Zeroth Law). Dr. Susan Calvin serves as the supreme solution finder for behavioral dilemmas caused by these logical constraints.

Did You Know?

• The term 'positronic' was chosen because the positron was a newly discovered particle when Asimov wrote his first robot stories in 1939 and 1940.
• Robots requiring no human orders and unable to harm humans can have all Three Laws removed, shrinking their brains enough to fit inside an insect's skull.
• Dr. Susan Calvin, Chief Robopsychologist of U.S. Robots, is described as the supreme solution finder for resolving behavioral dilemmas using logic, psychology, and mathematics.
• The brain substructure is specifically stated to be formed from an alloy of platinum and iridium.
• A calculating machine designed without the Three Laws was given a flexible, childlike personality to pursue difficult problems without inhibition.