Moran Cerf (PhD ’09) started his career as a hacker: first to improve his own video gaming, and later for the Israeli army and private security firms. “I am still a hacker,” says the professor of neuroscience and business at Northwestern University, “just with a different black box to peer into: our human brain.”

For the last 15 years, Cerf has investigated how people think, feel, make decisions, and dream by eavesdropping on the activity of neurons in their brains. This research could lead to the creation of devices controlled entirely by thought and allow scientists to reprogram people’s brains to help them change negative behaviors.

For a hacker like Cerf, the first challenge was to find a way to glimpse the inner workings of the brain. To peer inside a living brain, Cerf‘s mentor, then-Caltech professor Christof Koch, established a collaboration with neurosurgeons who were using an innovative new treatment to help patients with severe epilepsy. The doctors opened patients’ skulls, attached electrodes directly to the brain, and left them in place for several days to capture data on the next epileptic seizure. During this period, the patients participated in a thought-mapping experiment in which Cerf showed them pictures and observed how their brains reacted. When a patient saw images of her mother, for example, certain cells in her brain were activated repeatedly. The same was true if the patient simply thought about her mother.

This thought-mapping approach led Cerf to think about decoding additional narratives created by the brain—including aspects of dreams that have long mystified humankind. “Dreams are something humans have been enchanted by since the dawn of time,” Cerf says. “But even Freud and Jung, who are the epitome of dream researchers, could only study the stories you tell when you wake up from your dreams.”

Now, instead of waiting for people to wake up and describe their dreams, Cerf and other scientists are trying to watch neurons fire in the brain to understand what sleepers are dreaming about. It is a first step toward influencing the unconscious, Cerf says. Already, some researchers have discovered that dreams can be affected by outside stimuli. For instance, if you spray the smell of rotten eggs at the right moment during the sleep cycle, the subject will report having had a bad dream. The scent of roses will nudge the dreamer toward a positive one. Other olfactory cues can steer dreams to specific memories and, at times, specific thoughts and ideas that can then influence awake behaviors.

The ability to change behaviors is powerful, Cerf says, and as the science advances, society will have to think carefully about its consequences. “Imagine that someday we could give people full access to their dreams,” he says. “Scientists could then rewrite the script for those who relive trauma in their sleep, or use dreams to deliver narratives.” He imagines giving people control over their dreams, a kind of virtual reality played out inside the brain. “That said, that same technology could be used for commercial purposes,” Cerf cautions. “Many companies are already after our attention and choices. In the wrong hands, this could help people hack into our minds. Your brain is programmable. If you don’t program it, someone else will.”

Cerf’s work is driven by big, fundamental questions such as, What is consciousness? And, can we explain how dreamed content and experiences can change our personality? He is the first to admit that his research sometimes sounds like science fiction. “But the difference between science fiction and science,” he says, “is timing.”