Barrett is best known for her work on dreams and their contributions to creativity and objective problem solving. She interviewed modern artists and scientists about their use of their dreams, documenting dramatic anecdotes including Nobel Prizes and MacArthur 'genius grants' whose ideas originated in dreams. She also conducted research asking college students to incubate answers to real-life homework and other objective problems on which they were working, finding that in one week’s time, ½ had dreamed about their topic and ¼ had a dream which provided an answer. Barrett describes dreaming as simply “thinking in different biochemical state” and believes we continue to work on all the same problems...personal and objective...in that state. Her research concludes that while anything...math, musical composition, business dilemmas...may get solved during dreaming, the two areas dreams are especially likely to help are 1) anything where vivid visualization contributes to the solution, whether in artistic design or invention of 3-D technological devices and 2) any problem where the solution lies in thinking outside the box—i.e. where the person is stuck because the conventional wisdom on how to approach the problem is wrong.

Barrett has also conducted research on lucid dreams and on helping people suffering from PTSD to incubate mastery dreams to change their nightmares, and published studies tracking the progression of dreams during bereavement. She has studied characteristics of dreams in various disorders including depression and dissociative disorders. During the summer 2010 publicity about the dream-themed film Inception, Barrett was interviewed by media including ABC, NBC Today, CNN, WSJ, NYT, and USA Today, pointing out that some aspects of the film like lucid dreaming, control of one’s own dreams, and dreams-within-dreams were highly realistic while the control of others’ dreams, time slowing in dreams, and absolute impossibility of dreaming that you die were all fictional premises in the service of the thriller plot.

Barrett’s studies of hypnosis have focused on different types of high hypnotizables, finding two subgroups which she terms fantasizers and dissociaters. Fantasizers are people who have vivid imaginations, find it easy to block out real-world stimuli, spend much time daydreaming, report imaginary companions as a child and grew up with parents who encouraged imaginary play. Dissociaters usually had a history of childhood abuse or other significant trauma, had learned to escape into numbness, and to forget unpleasant events. Their association to “daydreaming” was often going blank rather than vividly recalled fantasies. Both score equally high on formal scales of hypnotic susceptibility.

Other research by Barrett focused on the similarities and differences of daydreams and nocturnal dreaming and on the significance of earliest memories as reflecting a microcosm of an individual’s worldview. Barrett is interested in film and has written on techniques which films use to represent dreams and on the negative stereotypes of hypnosis in film.

Most recently Barrett has written on evolutionary psychology, especially the concept of supernormal stimuli...the idea that technology can create an artificial object which pulls an instinct more strongly than that for which it evolved. The phrase "supernormal stimuli" was coined by the Dutch scientist Niko Tinbergen in the 1930's. Barrett's book Waistland (2007) explores the weight and fitness crisis in terms of supernormal stimuli for food and rest. Her latest book, "Supernormal Stimuli: How Primal Urges Overran Their Evolutionary Purpose" (2010) examines the impact of supernormal stimuli on the diversion of impulses for nurturing, sexuality, romance, territoriality, war, and the entertainment industry’s hijacking of our social instincts.