Dr. Parks did not respond to phone calls and e-mail messages.

Dr. Park holds medical patents from his various research studies.

"We wanted to ask a very basic question," Dr. Park said.

Dr. Park said police officers might be less likely than the studies' subjects to show unconscious bias, because of their training.

Dr. Park said those secondary findings were preliminary and needed to be confirmed by further research.

Dr. Parks conceded that the results are up for interpretation.

"I think you can probably take these numbers several ways," Dr. Parks said.

Dr. Parks said they sent out 2,200 requests and got 400 participants, a response rate of just under 20 percent.

The results of that test, Dr. Park says, are a personal matter.

Dr. Park listened attentively, and asked one or two questions.