University of Oregon physics professor Richard P. Taylor said the paintings do not match the drip patterns of other Pollock works, the New York Times reported Thursday.
Although Taylor's computer tests, using fractal geometry, do not prove the paintings owned by Alex Matter are fakes, the results cast doubt on their authenticity, the Times said.
The six paintings were among 24 Matter found in 2003 in Wainscott, N.Y. Matter's parents were friends of Pollock, the Times said.
Pollock scholar and Boston College art historian Claude Cernuschi said more than six of the 24 works should have been tested.
He noted Pollock used experimental techniques and said the differences found in the six works did not necessarily mean they were painted by someone else.
Matter plans to exhibit the works this year in honor of the 50th anniversary of Pollock's death.