Background
This photo is of 29 attendees at the meeting of the Society of Experimental Psychologists (SEP), held at Brown University in 1955. SEP is an invitation-only society founded by Edward Titchener in 1904. The notable psychologists of the mid-20th century pictured here include B. F. Skinner (3rd in 1st row), Neal Miller (5th in 1st row), George Miller (rightmost in 3rd row), and Bill Estes (rightmost in back row).
Image courtesy of Russell Church, from an annotated photo on the wall of the Psychology Department at Brown University.