1The Defining Decade Book ReviewIn Meg Jay's book The Defining Decade: Why Your Twenties Matter, Meg explains how one's actions in their twenties control and influence the rest of their life, hence the title of the work. Meg, a clinical psychologist with a PhD, constantly explains how people in their twenties often ironically procrastinate and push back their responsibilities, including their career and future family, even though this decade is what defines their career and their marital relationship the most. By providing scientific evidence that backs her ideas and claims, Meg is able to provide insight into why young adults in their twenties feel trivialized by their twenties, and why these beliefs are completely wrong and are actually the farthest from the truth.Meg begins her book by first giving insight into how people's careers are shaped by their twenties. She starts off by explaining the psychological concept of present bias, in which people in their twenties value give more weight to rewards that will come soon than bigger rewards that will come later. She relates this to the common misconception of how peoplein their twenties often procrastinate and would rather have some part-time job now and explore the career they really want to have later on in their thirties, even though the twenties are what defines one's career. Furthermore, she also relates the idea of present bias to identity development, and how people in their twenties spend their defining decade having fun and messing around, despite this decade having the biggest effect on who they become since the commitments and exploration done during this decade has the biggest lasting impact. Meg also explains Ericcson's psychological research on expertise and how it takes ten thousand hours for one to completely master something, and how people in their twenty years could easily master something if they set their mind to it. However, instead of doing this and developing their career,2many in their twenties choose to procrastinate and waste it away instead. Meg also explains the psychological concept of self-efficacy, or one's ability to produce their desired result. Self-efficacy is essentially a fancy word for confidence, which Meg explains is developed through experiencing both success and failure. As Meg puts it, "For work success to lead to confidence, the job has to be challenging and it must require effort. It has to be done without too much help...A long run of easy successes creates a sort of fragile confidence, the kind that is shattered when the first failure comes along. A more resilient confidence comes from succeeding—and from surviving some failures" (Jay 160). This allows Meg to demonstrate how taking action in one's twenties is almost always better than not, even if the action results in a failure. Failing and takingaway the experience of it is better than not acting or experiencing at all. Through this, Meg shows how it is necessary for people in their twenties to take action now, and not wait until later. She states that it is useless having a boundless array of choices if none of them are going to be chosen or committed to. Action needs to be taken for the results or experience to show, whether it is related to one's career, one's family, one's personal life, or one's development in general. Meg also goes on to explain how one's future family and marital relationship is often heavily influenced by one's twenties. Meg explains that dating down and dating anyone that chooses you is a bad plan of action. She states that dating and marriage shouldbe as intentional and carefully planned out as one's career should be, even though this is contradictory to what many people in their twenties believe. Through the psychological principles of similarity relating to attraction, Meg explains how the more similar people are, the more attracted they are to each other. However, similarity doesn't equate or correlate to success in one's marital relationship. As Meg explains, happiness in a marital relationship isn't based on if two people like the same things or have the same interests, but on how their personalities fit3each other's. Personality is a match maker, where as similarity isn't; While similarity correlates toattraction, personality correlates to a more successful and happy marriage. As Meg restates, "What counts in making a happy marriage is not so much how compatible you are, but how you deal with incompatibility" (Jay 112).Meg also explains how the brain, as well as one's attitude, relates to one's defining decades and the choices one makes during it. She explains that the frontal lobe, the part of the brain responsible for making judgments, choices, and reasoning, isn't finished developing until the mid-twenties, which is one's most important life decisions are made. Meg also gives insight into how one's beliefs can have an effect on one's decisions, specifically if one has either a fixed or a growth mindset. Meg defines a fixed mindset as one only being motivated and confident as long as they are successful- as soon as they encounter their first failure, they give up and stop trying, which is detrimental to one's growth, especially during their defining decade. A growth mindset is defined by Meg as being able to change and adapt, that success is something to be achieved. A person with a growth mindset would look at failures as opportunities to change and improve, where as a person with a fixed mindset would look at failures as impassable obstacles. Growth mindsets are necessary for one's defining decade, since failure is almost bound to eventually sprout up, and adapting to those failures is theonly way to improve and be successful in life; Quitting after the first failure will get you nowhere in life. As Meg wrote in her book, "In a longitudinal study of college students, freshmenwere evaluated for fixed mindsets or growth mindsets and then followed across their four years of enrollment. When the students with fixed mindsets encountered academic challenges such as daunting projects or low grades, they gave up, while the students with growth mindsets responded by working harder or trying new strategies" (Jay 158). Meg also goes on to explain4how not only is the critical period during one's childhood important, but the critical period duringone's adolescence and emerging adulthood are just as important. During one's childhood, language acquisition and attachment occur, both extremely important