Correct Answer: D

Rationale: The correct answer is 'D: deficits.' Most cognitive aging research has indeed focused on deficits rather than stability, gains, or competence. Studies have consistently shown that deficits in processing speed and memory are common in aging individuals, making it a primary area of interest in research. Choices A, B, and C are incorrect because cognitive aging research primarily aims to understand and address deficits associated with aging rather than focusing on stability, gains, or overall competence.

Correct Answer: B

Rationale: The correct answer is B: competitive athletes. Competitive athletes are often studied by researchers to investigate the impact of biological aging on motor skills because their performance is closely linked to physical abilities. Sedentary adults (choice A) may not provide a clear understanding of the relationship between biological aging and motor skills as they may not engage in consistent physical activity. Men in their mid- to late thirties (choice C) and women in their childbearing years (choice D) may not represent a group where motor skills are as finely tuned and critical to performance as in competitive athletes.

Correct Answer: A

Rationale: Physical activity is known to have a positive impact on mental health by reducing symptoms of anxiety and depression. Choice B is incorrect because physical activity generally improves both mood and alertness. Choice C is incorrect as physical activity tends to increase mood, alertness, and energy levels. Choice D is incorrect as physical activity actually increases neural activity in the cerebral cortex, which is associated with improved cognitive function and mental well-being.

Correct Answer: D

Rationale: According to Jean Piaget, equilibrium is the balance between what children already know (internal structures) and the new information they encounter. Imitation (choice A) is not directly related to this concept. Adaptation (choice B) involves adjusting to new information and is part of Piaget's theory, but it does not specifically refer to the balance between internal structures and external information. Cognition (choice C) is a broader term that encompasses mental processes, including thinking, learning, and problem-solving, but it is not specifically about the balance between internal structures and external information as equilibrium is.

Correct Answer: B

Rationale: According to the cognitive perspective of perceptual development, babies impose meaning on what they perceive. This means that babies actively interpret and make sense of the stimuli they encounter. Choice A is incorrect because babies are not seen as blank slates in this context; they actively engage with their environment. Choice C is incorrect as babies do not necessarily search for discontinuous stimuli, but rather interpret what they perceive. Choice D is incorrect as seeking variant features in the environment is not a core concept of the cognitive perspective of perceptual development.