Final answer:
A paper discussing the effect of the individual on the group and vice versa is likely authored by a social psychologist, as this field focuses on the influence of interpersonal and group relationships on behavior.
Step-by-step explanation:
A paper titled, The effect of the individual on the group, and vice versa, would most probably have been written by a social psychologist. This particular area of psychology examines how people affect one another and looks at the power of the situational factors.
The field of social psychology is interested in all aspects of personality and social interaction, exploring the influence of interpersonal and group relationships on human behavior. When examining how the presence of others impacts an individual's behaviors, thoughts, and feelings, social psychologists consider how people will change their behavior to align with the social situation at hand.