Explanation
Correct answer: A.
Choice A is the best answer because it presents a finding that, if true, would most directly support the idea that social buffering—the mitigation of stress by the presence of other animals of the same species—occurs among C. helleri. According to the text, the researchers quantified the amount of stress in C. helleri as the percent change between baseline and peak heart rate, with higher values indicating greater stress. The text also describes the researchers’ three treatments: snakes alone, snakes with a rope, and snakes with a companion C. helleri. If the average percent change in heart rate was lower among snakes with a companion than among either solitary snakes or snakes with a rope, that would indicate two things: snakes accompanied by a companion experienced less stress than they did when alone, and the reduction wasn’t simply the result of any object being present, since the rope didn’t produce the same effect. Together, these results would directly support the conclusion that the companion’s presence mitigated stress, as the social buffering hypothesis predicts.
Why the other choices are wrong
Choice B
Choice B is incorrect because the finding compares peak heart rates among the three treatments rather than the percent change in heart rates among those treatments. The finding also indicates that snakes with a companion and snakes with a rope showed no differences in peak heart rates. If a rope produced the same effect as a companion did, that would suggest that the effect, whatever its extent, isn’t caused specifically by the presence of another individual of the same species and so wouldn’t support the social buffering hypothesis.
Choice C
Choice C is incorrect because the finding addresses absolute baseline and peak heart rates rather than the percent change between them, which is the measure of stress response the researchers used. Lower absolute heart rates in companion-present snakes could reflect a generally calmer state but wouldn’t show that the stress response to the disturbance was reduced and so wouldn’t directly demonstrate social buffering as defined in the study.
Choice D
Choice D is incorrect because the finding states that the percent change in heart rate was smaller among solitary snakes than among snakes with a companion, which would indicate a smaller stress response when alone. This pattern would directly contradict the social buffering hypothesis rather than support it. Furthermore, a comparison of baseline heart rates would be immaterial for determining whether social buffering occurs among C. helleri because the text indicates that a change in heart rate, not average baseline heart rate, indicates a stress response.