YSM Issue 90.2

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FEATURE psychology UNDERSTANDING COOPERATION Theoretical model developed to explain human behavior ►BY CYNTHIA YUE Four people work in a group, each given a sum of money. They are asked if they wish to contribute some amount of money to the public pot. The choices are thus made clear: either selflessly contribute and allow the money to be evenly divided or selfishly keep the money and share in the amount contributed by the others. Such is the setup of a public goods game, which, like other game theory-related concepts like a prisoner’s dilemma, provides insight into inherent human behavior regarding cooperation and selfishness. These games have inspired the research conducted at Yale by Adam Bear, a fourth year Ph.D. candidate in Psychology, and David Rand, an Associate Professor of Psychology, Economics, and Management. Basing their work on empirical data related to these games, Bear and Rand have developed a theoretical game theory model that explains that people who intuitively cooperate but can also act selfishly succeed from an evolutionary perspective. To create the model, Bear and Rand used MATLAB to construct agent-based simulations consisting of virtual agents with all permutations of behaviors, which interact with one another in various environments through a computer system for several generations. Afterward, they made mathematical calculations to confirm the accuracy of their simulations. “The idea of these simulations is they’re meant to model some kind of evolution either over biological time or over cultural time,” said Bear. “People who tend to do well when they play their strategies are more likely to survive in the next generation than people who do poorly, so these agents interact on a set of generations, and once you do well, [you] tend to stay in the game; once you do poorly, you tend to die out.” The model itself takes several factors —such as type of thinking and environment—into consideration. With thinking, agents can either follow their intuition or use deliberation. Bear describes intuition as a form of cognition that uses heuristics—mental shortcuts—to get to answers quickly. This way of thinking is efficient but may lead to errors in reasoning due to its inability to reason through the details of the context one is facing. On the other hand, deliberation allows agents to take time to reason about the contexts and make more accurate decisions. In the model, agents can strategize, choosing how much intuition and deliberation to use. The environment refers to the proportion of repeated to oneshot interactions. Agents vary in how much they engage in one-shot interactions and repeated interactions, in which they may possibly establish a relationship. From an evolutionary standpoint for which success seems built on self-interest, Bear explains, “Say we’re in a repeated interaction: it’s better if I’m nice to you if I’m going to see you again,” said Bear. “But if I’m never going to see you again, say it’s a one-shot interaction and no one else is seeing us…I’m better off being selfish if it would cost me a lot to be nice to you.” The conclusions of Bear and Rand’s model focused on environments with more repeated interactions—as they more realistically reflect the environment of the real world, according to Bear. He described the best agent in their model: an agent that has a fast cooperative response, but selfish response upon deliberation in one-shot interactions. Their research, however, received critiques from others working in the field, particularly Kristian Myrseth, an Associate Professor in Behavioral Science and Marketing at Trinity College Dublin, and Conny Wollbrant, an Assistant Professor in Economics at the University of Gothenburg. “The model makes this crucial claim that evolution never favors strategies...where deliberation increases your prosocial behavior,” Myrseth said. Wollbrant added, “The problem is that we know today, we’re fairly sure, that…people are often behaving prosocially, not for strategic reasons, but because they feel that’s the right thing that they should do.” These two researchers claim that the model does not allow cases of inherent prosocial behavior to survive despite the apparent evolution of people with such behavior existing in the world today. Nevertheless, according to Bear, he and Rand have continued to work on additional versions of the model to make it more realistic by incorporating how intuition and deliberation may not be so black and white in terms of distinguishing the environment. “There was this fun process of discovery in the model and learning what the model was actually showing,” said Bear. “It’s cool because you know you think when you model something, maybe it’ll be obvious what you’re going to find, but actually, you discover these interesting things that you didn’t necessarily anticipate before modeling.” IMAGE COURTESY OF REYNERMEDIA ►Agents who intuitively cooperate, but deliberate and defect to selfish behavior in one-shot interactions, succeed evolutionarily. 34 Yale Scientific Magazine March 2017 www.yalescientific.org
INN VATI N STATION Fighting Battery Fires with Microfibers ►BY ALAN LIU From the phone you’re holding to high-powered electric cars, lithium-ion batteries are found in nearly every rechargeable electric device. Since their invention in the 1970s, they have been widely used in household gadgets. In contrast to typical single-use alkaline batteries, lithium-ion batteries contain a much denser concentration of energy stored in rechargeable cells. However, because of their highenergy concentration, these batteries tend to heat up quickly as they discharge, becoming dangerous fire hazards. In the past couple of months, these risks have been highlighted by the Samsung Note 7 explosions, when those phones ignited right in their users’ palms, and by the hoverboard fires, which led to bans of hoverboards in many public places—including Yale’s campus. New research at Stanford may provide the ideal solution to these unintentional dangers. While scientists have already found some ways to lower heat generation of charging and discharging batteries, these methods often don’t protect against other issues like manufacturing inconsistencies. For example, in the Samsung Note 7 explosions, already-existing heat reduction systems were unable to get around a structural issue: there was a weak spot in the separator between the positive and negative ends of the battery. This separator was designed to keep the two ends, storing positive and negative ions, from touching each other, so that the battery wouldn’t instantly discharge all of its stored energy. This situation is akin to a pile of baking soda wrapped in tissue paper, hanging above a jar of vinegar. A hole or a weak spot in the paper would cause all of the baking soda to fall out and fall into the vinegar, creating an ever-expanding pile of foam. The tissue paper acted as a separator that kept the baking soda apart from the vinegar. Similarly, in the battery, if the separator had a weak spot, the ions would spill over and mix, creating a short circuit that would heat up the flammable liquid inside the lithium-ion battery. The entire battery would then ignite in an explosive reaction. Another option to reduce the risk of fire is to dilute the flammable liquids inside the battery with anti-flammable ones like triphenyl phosphate (TPP). However, this severely deteriorates the conductivity of the liquid inside the battery, reducing overall efficiency. Although a shorter battery life is much better than third-degree burns, in the increasingly competitive market for smartphones and consumer electronics, every advantage is a valuable one. Recent advances in battery innovation may provide a way to salvage this advantage. In January 2017, researchers in the Yicui lab at Stanford made lithium-ion batteries less flammable without hurting their performance by developing their own custom separators. The separators were woven from sophisticated microfibers with nanometer-scale diameters. In contrast to classical separators, these new ones contain the anti-flammable TPP as a built-in safety mechanism. To create this fine thread, the researchers used electric force to solidify a mixture of chemicals containing TPP in midair as it fell from the tip of a syringe. They then tested this thread to ensure the presence of two distinct layers: the inner layer contains TPP, and the outer layer is thick enough to almost completely stop TPP from leaking into the electrolytes. In addition, the thin outer shell is designed to melt away if the battery becomes excessively hot. In that case, TPP flows out of the thread and completely dissolves in the liquid to reduce the heat, similarly to how an automatic sprinkler system activates to put out fires. This solution addresses the need for a reliable thermal failsafe that doesn’t affect battery performance, making it ideal for consumer electronics like phones or hoverboards. Here at Yale, Jaehong Kim, a professor in the Department of Chemical and Environmental Engineering, is performing similar research, working on a separator that is similar, but is used for water filtration and treatment instead of battery safety. Kim’s work focuses on helping the membrane maintain functionality and increasing its durability through a selfhealing feature. If a membrane used for treating drinking water is damaged, it creates risks such as the outbreak of waterborne pathogens. Repairing these filters often requires a system shutdown to replace the membrane, which is especially a concern in places without the infrastructure to support such delays. Although the aftereffects aren’t as explosive as battery malfunctions, an outbreak of disease could be even more disastrous for affected communities. For both membranes and battery separators, one thing is clear: we should not need to sacrifice safety to achieve efficiency. www.yalescientific.org March 2017 Yale Scientific Magazine 35
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YSM Issue 90.2

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