Final answer:
A behaviorist is the psychologist most likely to engage in an observational assessment of personality, as their focus is on observable behaviors in understanding personality traits.
Step-by-step explanation:
The psychologist most likely to be engaged in an observational assessment of personality would be a behaviorist. A behaviorist focuses on observing and measuring behaviors as a way to understand and predict personality traits and tendencies. This methodology aligns well with observational assessments, where the researcher is an outside observer documenting behaviors in a naturalistic or controlled setting. On the contrary, a psychoanalyst would rely on in-depth interviews and meetings to understand the unconscious mind, a humanistic psychologist would emphasize individual growth and self-actualization, and a cognitive psychologist would focus on internal mental processes such as thinking and memory.