Stephen Kosslyn, a prominent young cognitive psychologist at Johns Hopkins University, confirmed this week that he has accepted an offer of tenure in Harvard's Psychology and Social Relations Department.

"I'm definitely coming back." Kosslyn, an associate professor here from 1977 to 1981, said. "I'm really looking forward to working with the students there."

Kosslyn said he sent his letter of acceptance to Dean of the Faculty Henry Rosovsky last week.

Kosslyn, acknowledged to be a top expert in the new field of mental imagery, this year won the prestigious National Academy of Sciences award for outstanding research scientist 35 years or younger, professors at Harvard reported this week.

But Kosslyn said he is embarking into another new field, which he calls computational neuropsychology. This subject involves the relation of neurobiology to psychological mental processes Kosslyn said he will travel to Lebanon, N.H., this week to do research on a "split brain" patient a person whose cerebral hemispheres are not connected Kosslyn added he plans to continue research in this field at Harvard.

Colleagues and students who remember Kosslyn's days at Harvard were uniformly enthusiastic about his return.

"I was very pleased with the offer Rosovsky and the department made me." Kosslyn said, terming it "sufficiently better" than Hopkins's tenure offer.