Stockholm, Sweden ? Sharing the Nobel Prize for economics Wednesday was Daniel Kahneman, 68, a U.S. and Israeli citizen based at Princeton University in New Jersey.

Kahneman has integrated insights from psychology into economics, “especially concerning human judgment and decision-making under uncertainty,” the Royal Swedish Academy of Sciences said in its citation.

His experiments in probability theory showed a shortsightedness in interpreting data that could explain large fluctuations on financial markets and other phenomena that elude existing models, the academy said.

Wednesday’s announcement of the 2002 Nobel Memorial Prize in Economic Sciences was the second Nobel of the day. The chemistry award went to John B. Fenn of the United States, Koichi Tanaka of Japan and Kurt Wuethrich of Switzerland for inventing techniques used to identify and analyze proteins that have revolutionized the search for new medicines.

The techniques are also proving useful for diagnosing some cancers.

Fenn, 85, of Virginia Commonwealth University in Richmond, and Tanaka, 43, of Shimadzu Corp. in Kyoto, Japan, will share half of the $1 million prize. The other half of the prize goes to Wuethrich, 64, a scientist with the Swiss Federal Institute of Technology in Zurich and the Scripps Research Institute in San Diego.

Because of their work, “chemists can now rapidly and reliably identify what proteins a sample contains,” the Royal Swedish Academy of Sciences said.

“They can also produce three-dimensional images of protein molecules in solution. Hence, scientists can both ‘see’ the proteins and understand how they function in the cells.”

Fenn and Tanaka produced their breakthroughs in the latter half of the 1980s, transforming an analysis technique called mass spectrometry, which lets scientists rapidly identify a substance. Mass spectrometry is used in tests for doping and illegal drugs, for example.

Wuethrich was honored for improving a technique called nuclear magnetic resonance. The technique allows scientists to develop three-dimensional images of molecules in a solution, which is the natural environment of a protein in a cell.

Wuethrich’s work allowed the technique to be used on large molecules like proteins. The first complete protein structure to be determined with his method was achieved in 1985.

The medicine, physics, chemistry, literature and peace prizes were first awarded in 1901. The Nobel Memorial Prize in Economic Sciences was established separately in 1968, but it is grouped with the other awards.

Nobel Foundation statutes stipulate that no more than three winners can share a prize, and the committees often choose the maximum number, finding it hard to single out researchers. Often the awards are given for discoveries made after decades of research.