"Investigation of the laws of mental health, and the taking of measures for…

Mental Hygiene is the branch of psychology concerned with promoting, preserving, and restoring positive mental health. Pioneering psychologists each framed this idea differently: some through prevention of disorder, some through harmony of personality, some through adjustment to one's surroundings, and some through the ongoing investigation and application of the laws that govern mental health.

The stem echoes, almost word for word, the definition given by the psychologist Drever: mental hygiene is the investigation of the laws of mental health and the taking (or advocacy) of measures for their maintenance. Because the stem's phrasing centres on investigating the laws of mental health and maintaining them, it points to this specific definition.

Why the other names do not fit this specific phrasing:

• Shaifer is linked to an adjustment-centred approach to mental hygiene (from his work on the psychology of adjustment) - concerned with an individual's personal adaptation, not with investigating and maintaining the laws of mental health.

• Headfield defined mental health as the full, harmonious functioning of the whole personality - a personality-harmony idea, not an investigate-and-maintain-the-laws idea.

• Ladell defined mental health as the ability to make adequate adjustments to one's environment on the plane of reality - an environment-adjustment idea, not an investigate-and-maintain-the-laws idea.

Only the definition that centres on discovering and upholding the laws of mental health matches the stem, which is why Drever is the correct answer.