In the late 1960s, cognitive psychologists Jerome L. Singer of Yale University and John S. Antrobus of the City College of New York, created a daydream questionnaire. The questionnaire, called the Imaginal Processes Inventory (IPI), has been used to investigate daydreams. Psychologists Leonard Giambra and George Huba used the IPI and found that daydreamers' imaginary images vary in three ways: how vivid or enjoyable the daydreams are, how many guilt- or fear-filled daydreams they have, and how "deeply" into the daydream people go.