Nobel Prize-winning psychologist Daniel Kahneman has passed away at the age of 90.

He was widely known for his contributions to behavioral economics, despite never formally studying economics.

Kahneman gained fame with his best-selling book “Thinking, Fast, and Slow,” which challenged the idea that humans are purely rational beings acting in self-interest. Instead, he argued that people often act based on instinct.

His death was confirmed by Princeton University, where he had been a faculty member since 1993.

“Danny was a giant in the field, a Princeton star, a brilliant man, and a great colleague and friend,” said Professor Eldar Shafir. “Many areas in the social sciences simply have not been the same since he arrived on the scene. He will be greatly missed.”

Daniel Kahneman was born in Israel in 1934 and spent much of his early life in Nazi-occupied France, where his father worked in a chemical factory.

The family later moved to British-ruled Palestine in 1948, just before the establishment of Israel as a state.

Kahneman graduated from the Hebrew University of Jerusalem in 1954 before pursuing a doctorate in psychology at the University of California, Berkeley, in 1958.

In 1961, he returned to Jerusalem to start his academic career as a psychology lecturer, where he crossed paths with Amos Tversky, a cognitive psychologist. Together, they were awarded the Nobel Prize in Economic Sciences in 2002.

Their collaboration laid the groundwork for “Thinking, Fast, and Slow,” a seminal work published in 2011 that delved into the psychology of decision-making. The book outlined two systems that drive human thinking and decision-making: the fast, intuitive, and emotional system, and the slower, more deliberate, and logical system.

According to Kahneman’s analysis, our fast, intuitive mind often dominates decision-making, leading to potential errors in judgment.