Final answer:
The similarity between animals exposed to inescapable shock and depressed humans is altered neurotransmitter levels, indicating a shared characteristic of brain chemistry changes resulting from perceived lack of control in stressful situations.
Step-by-step explanation:
The similarity between animals exposed to inescapable shock and depressed humans is C) Altered neurotransmitter levels. Research has shown that in situations where animals experience uncontrollable stress, like inescapable shocks, they begin to exhibit behaviors and physiological responses that resemble symptoms of depression in humans. This condition, known as learned helplessness, is characterized by a sense of lack of control and leads to changes in brain chemistry, particularly in the levels of neurotransmitters, which can affect mood and behavior.
Further experiments like those of Martin Seligman in the 1960s have indicated that the presence or absence of controllability in adverse situations can affect subsequent behavior and brain physiology, including the amygdala's activation. Such findings have been paralleled in human studies, where depressed individuals have shown alterations in neurotransmitter systems, not unlike the changes observed in animals subjected to uncontrollable stress.
While increased activity levels, improved cognitive performance, and enhanced motivation to escape may occur in various contexts, they are not similarities shared specifically by animals exposed to inescapable shock and depressed humans. On the contrary, both may show a reduction in these as a response to a perceived lack of control over stressful situations.