Title: Leveraging Double Descent for Scientific Data Analysis: Face-Based Social Behavior as a Case Study. Abstract: Scientific data analysis often involves making use of a large number of correlated predictor variables to predict multiple response variables. Understanding how the predictor and response variables relate to one another, especially in the presence of relatively scarce data, is a common and challenging problem. Here, we leverage the recently popular concept of ``double descent'' to develop a particular treatment of the problem, including a set of key theoretical results. We also apply the proposed method to a novel experimental dataset consisting of human ratings of social traits and social decision making tendencies based on the facial features of strangers, and resolve a scientific debate regarding the existence of a ``beauty premium'' or ``attractiveness halo,'' which refers to a (presumed) advantage attractive people enjoy in social situations. We demonstrate that more attractive faces indeed enjoy a social advantage, but this is indirectly due to the facial features that contribute to both perceived attractiveness and trustworthiness, and that the component of attractiveness perception due to facial features (unrelated to trustworthiness) actually elicit a ``beauty penalty'', which has also been reported in the literature. Conversely, the facial features that contribute to trustworthiness and not to attractiveness still contribute positively to pro-social trait perception and decision making. Thus, what was previously thought to be an ``attractiveness halo'' is actually a ``trustworthiness halo'' plus a ``beauty penalty.'' Moreover, we see that the facial features that contribute to the ``trustworthiness halo' primarily have to do with how smiley a face is, while the facial features that contribute to attractiveness but actually acts as a ``beauty penalty'' is anti-correlated with age. In other words, youthfulness and smiley-ness both contribute to attractiveness, but only smiley-ness positively contributes to pro-social perception and decision making, while youthfulness actually negatively contribute to them. A further interesting wrinkle is that youthfulness as a whole does not negatively contribute to social traits/decision-making, only the component of youthfulness contributing to attractiveness does.