"the conference of psychologists at which the ideas of community psychology and the participant-conceptualizer role were first defined"

The correct answer is Swampscott.
The conference of psychologists which took place in Swampscott, Massachusetts, in 1965, was instrumental for the birth of community psychology and the participant-conceptualizer role. Community psychology deals with studying someone's psyche and mental abilities as part of a particular community and the society in general.