0:00:00.009,0:00:04.599 The debate between nature and nurture is almost as old as the chicken versus the egg. 0:00:04.610,0:00:06.409 What is more likely to influence how we 0:00:06.420,0:00:09.319 actually develop a personality and how we behave? 0:00:09.329,0:00:13.079 Is it the genes that we're born with? or, Are we taught and molded by our parents, 0:00:13.090,0:00:14.500 our school teachers, and our culture? 0:00:14.510,0:00:18.190 Behaviorist and humanist perspectives take on the nurture side of the debate. 0:00:18.200,0:00:20.049 They believe that you can become anyone you want 0:00:20.059,0:00:22.270 to with the right environment and the right stimuli. 0:00:22.280,0:00:24.170 But let's talk about the nature side, 0:00:24.180,0:00:28.180 the biological perspective of personality gives us more questions and answers 0:00:28.190,0:00:30.856 to think about as we reflect on our own personalities. 0:00:30.865,0:00:34.576 So, first off, I need to talk about something called evolutionary psychology. 0:00:34.585,0:00:38.116 Some of the earliest and most famous examples of the biological 0:00:38.125,0:00:41.465 perspective is ideas that were brought forth by Charles Darwin. 0:00:41.476,0:00:44.256 Darwin was the father of evolutionary psychology. 0:00:44.265,0:00:48.796 Now, his theories of evolution suggested that species evolve over time, 0:00:48.805,0:00:52.986 small adaptations happen throughout time that turn into species evolving. 0:00:52.995,0:00:55.995 He said that members of the same species with stronger traits were 0:00:56.006,0:00:59.236 more likely to reproduce and pass those traits onto the offspring. 0:00:59.245,0:00:59.476 Now, 0:00:59.486,0:01:02.111 evolution doesn't just favor physical traits like taller 0:01:02.122,0:01:04.092 people or people who are faster at swimming. 0:01:04.101,0:01:07.132 This theory actually suggests that our personality comes from 0:01:07.141,0:01:09.132 an environment that favored certain traits over time. 0:01:09.141,0:01:11.132 For example, in places where it's really hot, 0:01:11.141,0:01:13.501 people have more melanin in places where it's really cold, 0:01:13.512,0:01:14.991 people usually have less melanin. 0:01:15.001,0:01:17.611 Now, if the environment can change our physical biology, 0:01:17.622,0:01:21.772 who's to say that it can't change our cognitive biology and our personality? 0:01:21.781,0:01:24.162 So let's talk a little bit about the genes and the brain. 0:01:24.171,0:01:26.582 So where do biologists find our traits? 0:01:26.592,0:01:29.872 Well, they would say they find them in our genes and our genetics in our brain. 0:01:29.938,0:01:33.447 To test this theory, psychologists have studied identical twins. 0:01:33.458,0:01:37.708 Now, identical twins always have the same genes, the same genetic makeup, 0:01:37.718,0:01:41.708 but those who are separated at birth will be grown in two different environments. 0:01:41.718,0:01:44.307 So when scientists look at their similarities and differences, 0:01:44.318,0:01:46.297 they can get a really good idea on what is 0:01:46.307,0:01:49.587 actually nature and what is actually nurture from the environment. 0:01:49.597,0:01:51.568 So using these identical twin studies, 0:01:51.578,0:01:53.227 we can actually start to narrow down what 0:01:53.237,0:01:55.648 percentage of traits may be due to genetics. 0:01:55.657,0:01:58.708 If a trait can be passed down through a gene, we call it heritable. 0:01:58.718,0:01:59.847 You might have heard this word before. 0:01:59.914,0:02:02.573 Heritability is a variance between multiple people that 0:02:02.583,0:02:04.704 can be accounted for by genetic differences. 0:02:04.713,0:02:08.083 Now, basically that is a lot of words to say that with research, 0:02:08.092,0:02:10.622 we can tell how much of someone's behavior is really from 0:02:10.633,0:02:13.333 their genes and how much of it is from their environment. 0:02:13.343,0:02:16.464 In short, we can tell if something is nature or nurture. 0:02:16.473,0:02:16.623 Now, 0:02:16.634,0:02:18.983 some of our personality traits are influenced by 0:02:18.994,0:02:20.804 genes and some of them are actually not. 0:02:20.813,0:02:24.203 For example, according to the identical twin personality research, 0:02:24.214,0:02:27.533 some of these traits have been correlated to be influenced by genetics. 0:02:27.544,0:02:29.824 For example, social closeness is only 15 0:02:30.039,0:02:31.320 percent due to your genetics. 0:02:31.330,0:02:32.800 So a lot more of it has to do with the 0:02:32.809,0:02:36.559 environment that you were raised in. Achievement orientation is 38%. 0:02:36.570,0:02:40.460 Traditionalism is 59% which means it's about half and half nature and 0:02:40.470,0:02:45.100 nurture and imagination being 74% is mostly due to your genes. 0:02:45.110,0:02:49.720 One example of a gene that can influence a trait is the dopamine four receptor gene. 0:02:49.729,0:02:49.779 Now, 0:02:49.789,0:02:51.720 this gene has actually been connected with the trait 0:02:51.729,0:02:54.899 of thrill seeking and people enjoying something called novelty. 0:02:54.910,0:02:58.460 Now, novelty basically means new and fun and exciting ideas. 0:02:58.470,0:03:02.376 So there's a perfect example that a gene can actually cause a personality trait. 0:03:02.386,0:03:04.255 Although even though that term isn't right, 0:03:04.266,0:03:07.835 we don't say that they caused a trait and I'll explain that in the rest of this video. 0:03:07.845,0:03:12.636 Take the Jim twins as a real life example, that traits can be passed via genes. 0:03:12.645,0:03:16.335 Jim Lewis and Jim Springer were identical twins at birth. 0:03:16.345,0:03:19.136 They were separated though. They finally connected at the age of 0:03:19.145,0:03:22.755 39 and they quickly made headlines for their very similar lives. 0:03:22.766,0:03:23.876 This is actually kind of weird. 0:03:23.886,0:03:25.136 Both were the same height, 0:03:25.145,0:03:28.016 basically the same weight and they had very similar habits. 0:03:28.026,0:03:29.735 What's even weirder is that both of these twins 0:03:30.022,0:03:34.841 had both been married twice, and the women that they married had the same first names; 0:03:34.852,0:03:38.151 their first wife's name was Linda, and the second wife's name was Betty. 0:03:38.162,0:03:39.811 Now, they also drove the same car. 0:03:39.822,0:03:43.472 Now you might be wondering how crazy are these similarities? It's unpredictable. 0:03:43.481,0:03:46.361 Well, not everything about the Jim twins was similar, 0:03:46.371,0:03:49.171 they wore different hairstyles and they chose different professions. 0:03:49.182,0:03:52.472 But the story of the Jim twins and other studies of identical twins 0:03:52.481,0:03:56.501 show that our genes may be very closely correlated with our personality traits 0:03:56.511,0:03:59.908 and the decisions that we make. Other studies show just how important our 0:03:59.917,0:04:04.268 brain chemistry is to our reactions and how we actually assess our environment. 0:04:04.277,0:04:07.787 Different parts of the brain, so called, go off whenever we make decisions. 0:04:07.798,0:04:09.667 So the stronger that these responses are, 0:04:09.677,0:04:12.188 the more likely a person is to hold certain personality traits. 0:04:12.197,0:04:14.628 For example, as I'll talk about in future videos, 0:04:14.638,0:04:19.088 people who are highly neurotic also have stronger responses and their amygdala, 0:04:19.096,0:04:22.108 the part of the brain that is responsible for reacting to fear. 0:04:22.118,0:04:24.167 So, biological theorists of personality, 0:04:24.178,0:04:27.738 they believe that by changing the size of your amygdala, theoretically, 0:04:27.747,0:04:30.204 we could change how neurotic you are—that, is if you 0:04:30.213,0:04:33.164 can actually control the size of a particular brain section. 0:04:33.174,0:04:36.764 Now, the physical structure of the brain may also be linked to personality traits. 0:04:36.773,0:04:40.354 Studies from Cambridge University revealed a positive correlation between 0:04:40.364,0:04:43.484 openness and more folding in the prefrontal cortices. 0:04:43.493,0:04:46.604 So next, I'd like to talk about changes in brain chemistry. 0:04:46.614,0:04:47.764 So as we move on, 0:04:47.773,0:04:51.884 it is really easy to write off the nature theory as something that you cannot change. 0:04:51.894,0:04:54.884 Many people believe that if you're born with an aggressive temperament, 0:04:54.894,0:04:56.514 you really can't do much to change your 0:04:56.523,0:04:58.884 genes and your tendencies to actually be aggressive. 0:04:58.894,0:05:00.700 However, that's not, not exactly true. 0:05:00.709,0:05:02.820 Our brains have the potential to change 0:05:02.829,0:05:04.720 and actually cause our personality to change. 0:05:04.730,0:05:08.679 One famous example of this is the case of that of Phineas Gauge. 0:05:08.690,0:05:11.700 Phineas Gauge was a railroad worker in the eighteen forties. 0:05:11.709,0:05:14.859 Well, while working, he actually suffered a serious accident, 0:05:14.869,0:05:17.899 an explosion sent a tamping iron straight into his head 0:05:17.910,0:05:20.070 and it damaged a very large part of his brain. 0:05:20.079,0:05:22.839 He actually, I think should have been dead, but he survived. 0:05:22.850,0:05:26.959 He somehow survived the horrific accident but not without consequences. 0:05:26.970,0:05:29.579 They sent him to the hospital and got him fixed up. When Gauge 0:05:29.746,0:05:31.675 came back to work after his accident... 0:05:31.686,0:05:32.596 I don't know about you, 0:05:32.605,0:05:34.876 but I would not go back to work if something like that happened to me. 0:05:34.885,0:05:38.485 Well, anyways, his co-workers noticed some serious changes in his personality. 0:05:38.496,0:05:42.045 He wasn't as friendly and he was more prone to using profane language. 0:05:42.055,0:05:43.756 He was a changed man. 0:05:43.765,0:05:45.436 And his case is a prime example of 0:05:45.446,0:05:48.415 how a brain injury can severely affect personality, 0:05:48.425,0:05:51.205 which is great evidence for the biological model. 0:05:51.216,0:05:53.515 So other things like drugs, poor physical health, 0:05:53.526,0:05:56.425 and even smartphones have the ability to actually change 0:05:56.436,0:06:00.571 our brain chemistry and thus potentially affect our personality. 0:06:00.582,0:06:03.212 So due to the principle of neuroplasticity, 0:06:03.221,0:06:05.911 which means that we can essentially rewire our brain, 0:06:05.921,0:06:07.411 we can also come to the conclusion that 0:06:07.421,0:06:10.141 we can change our brain chemistry and ultimately, 0:06:10.152,0:06:11.552 we can change our personality. 0:06:11.562,0:06:12.791 So as I wrap this video up, 0:06:12.802,0:06:14.131 I'd like to offer a little bit more of 0:06:14.141,0:06:16.432 my thoughts on the nature versus nurture debate. 0:06:16.441,0:06:20.111 Lessons from the biological perspective of personality and behaviorism, 0:06:20.122,0:06:24.221 both offer convincing arguments that nature or nurture influence personality. 0:06:24.231,0:06:26.011 So, which side is the winner? 0:06:26.022,0:06:30.328 Now, I personally believe that nature and nurture are like ingredients in a cake. 0:06:30.338,0:06:32.388 You see to make a cake, you need flour, 0:06:32.398,0:06:34.338 you need eggs, and baking soda, and maybe a 0:06:34.347,0:06:36.667 few other ingredients to actually make a cake. 0:06:36.678,0:06:39.507 But do we say that flour causes a cake? 0:06:39.518,0:06:43.238 Not really, we need a little bit of both flour and eggs and those other ingredients. 0:06:43.247,0:06:45.638 And only after we make a whole bunch of cakes, 0:06:45.648,0:06:47.467 can we actually start to see what happens 0:06:47.477,0:06:49.708 when we add or subtract different ingredients? 0:06:49.717,0:06:54.227 So flour doesn't cause a cake. Genes don't cause personality. 0:06:54.238,0:06:57.167 However, each part is an important section of the whole. 0:06:57.178,0:06:59.428 We can connect certain tendencies to act 0:06:59.674,0:07:01.373 certain way to different parts of the brain. 0:07:01.384,0:07:04.683 When Phineas Gauge's personality changed literally overnight, 0:07:04.694,0:07:05.364 for example, 0:07:05.373,0:07:07.343 psychologists could pinpoint what parts of his 0:07:07.354,0:07:10.003 missing brain had influenced certain traits. 0:07:10.014,0:07:10.563 However, 0:07:10.574,0:07:12.743 other personality traits are influenced greater 0:07:12.753,0:07:14.764 by our environment and our culture. 0:07:14.773,0:07:17.044 So if we're taught to value agreeableness and we grew 0:07:17.053,0:07:19.644 up in an environment where being agreeable is easily, 0:07:19.653,0:07:23.084 we're probably going to be more likely to find ways to be agreeable. 0:07:23.093,0:07:27.424 So our personality is influenced by nature or nurture. I personally say both. 0:07:27.433,0:07:28.753 If you guys enjoyed this video, 0:07:28.764,0:07:31.350 feel free to watch some of other videos in the personality series. 0:07:31.359,0:07:32.700 I've worked really hard on them. 0:07:32.709,0:07:34.929 Now, if you want to learn more about your own personality, 0:07:34.940,0:07:36.269 you can go ahead and check out my free 0:07:36.279,0:07:38.640 three in one personality quiz in the description below. 0:07:38.649,0:07:40.850 I actually hired a web developer to create it. 0:07:40.859,0:07:44.119 It combines three of the major personality quizzes into one 0:07:44.130,0:07:46.059 test that you can take in under 10 minutes. 0:07:46.070,0:07:47.609 And I've also done some research and I'm going 0:07:47.619,0:07:48.910 to try to predict some things about you, 0:07:48.920,0:07:52.890 like your political stances, your relationship style, and even your health. 0:07:52.899,0:07:54.980 So you can go ahead and check that out in the description below. 0:07:54.989,0:07:58.619 I hope you guys enjoy this video and most of all, I hope you learned something. 0:07:58.630,0:07:59.540 Thank you for watching.