The goal of this clinical trial is to learn more about decision making in psychosis spectrum disorders, like schizophrenia. Participants will be people who have had symptoms of a psychosis spectrum disorder start within the last five years. The investigators will study how two study agents change decision making in people with psychosis, by asking participants to complete some brain games on the computer before and after taking the study agents. The investigators hope to improve our understanding of psychosis to help people in the future. The main research questions are:
* Does a single dose of modafinil change how people with psychosis play the brain games?
* Does a single dose of d-serine change how people with psychosis play the brain games?
* Does a single dose of modafinil change brain activity?
* Does a single dose of d-serine change brain activity?
Participants will:
* Complete an interview and self-report questionnaires.
* Complete safety screening activities, like a blood draw, a urine drug test, and an alcohol breathalyzer test.
* Complete functional Magnetic Resonance Imaging (fMRI) scans. fMRI uses magnets to take pictures of the brain. There will be six scanning appointments in the study, with two scans each. Appointments will be about a month apart.
* Take a single dose of a study agent during each scanning appointment. The study agent will be taken after the first fMRI. There are three study agents in total: modafinil, d-serine, and a placebo. Each participant will take each study agent twice during the study.
* Play brain games on a computer that measure decision making, thinking, and problem solving skills