In this episode, Dr. Carl Sagan commemorates the 30th anniversary of his PhD defense. He talks about his dissertation, why he chose evolutionary psychology, and how it can be applied to a wide range of problems.
00:00:00.000So 30 years ago today, as a matter of fact, not just 30 years ago today, probably to the hour.
00:00:11.480So I defended my doctoral dissertation at Cornell, and the defense was on January 21st, 1994, so it's exactly 30 years ago.
00:00:23.260I remember my wife yesterday asked me, do you remember what day it fell on, like what day of the week?
00:00:27.960And I said to her, oh, I think it was on a Tuesday.
00:00:32.200And then she checked, and it turned out to be on a Tuesday.
00:00:36.980And it was in the afternoon, I think it was probably a bit earlier, I think it was maybe from 2 to 4, if I'm not mistaken.
00:00:44.140So probably by now, I had finished, or just about finished.
00:00:48.280And I remember as the committee asked me to step outside the room so that they can deliberate, and then they opened the door and asked me to come back in and so on.
00:00:59.940My doctoral supervisor was the first one who approached me and said, put out his hand and said, congratulations, doctor.
00:01:10.680So that was the first time that I switched from mister to doctor in obtaining the PhD.
00:01:18.000The title of the PhD was The Adaptive Use of Stopping Policies in Sequential Consumer Choice.
00:01:27.060I mean, saying really consumer is too restrictive, because really, the doctoral dissertation could be applied in consumer choice.
00:01:40.600But of course, it could be applied to any choice.
00:03:04.720Anyways, there are four screenshots, as I said, that are really helpful if you want to follow the details of what the doctoral dissertation is about.
00:03:16.900And I mean, I'm taking the time today to mark the moment.
00:03:20.460Of course, number one, because it is an important moment.
00:03:26.360It's the 30-year anniversary of my defense.
00:03:30.040By the way, I'm 59, so when I defended my dissertation, I was 29, and now it's been 30 years since I've defended it.
00:03:38.900So now I've gone to the meaning that I've longer lived having defended my PhD than before I had defended my PhD.
00:03:47.700I am a sentimental and romantic person, so I keep thinking about all these numbers issues.
00:03:53.220So, okay, a few people have put their thumbs up so you have those four screens, screenshots, which will be really important.
00:04:02.740One of the things, by the way, that I'm really looking forward to, I hope that as Elon Musk develops the video capabilities of X Spaces,
00:04:13.640I'll be able to have not just audio lectures, but audio-visual lectures on X.
00:04:19.920Imagine I could just turn it on and, you know, a thousand people could be sitting and actually listening to a lecture that I've put together.
00:04:29.160But for now, since we don't have that ability, I thought giving you that visual aid would help.
00:04:33.900Okay, so what is the general problem first, and then I'll get into the bit of the weeds.
00:04:39.640And I'm saying this not because it was, you know, my PhD, but really because objectively, it truly, fully explains how people make decisions across any decision process.
00:04:56.420One of the things that, if any of you have followed my work in general, know about me, is that I'm a synthetic thinker.
00:05:03.960In other words, I like to study problems and use frameworks that could be applied in many, many contexts.
00:05:11.400So evolutionary psychology is something that I've dedicated my academic career to because I can use evolutionary psychology to study politics or economics or mate choice or consumer behavior, you know, or psychiatric conditions in medicine.
00:05:27.200And these are all fields that I have published in, so one of the reasons why that particular dissertation topic is the one that I ended up working on is because I very quickly realized that it is applicable to any decision that we make from the most consequential to the most inconsequential ones.
00:05:49.100Okay, so let's discuss the fundamental problem.
00:06:19.100Contrary to what classical economists tell us, see, classical economists think that in order for you to maximize your utility, you need to look at all available and relevant information.
00:06:32.320Otherwise, if you only look at a subsample of the information, then you can't be assured that the choice that you've made is the optimal one from a utility maximization perspective.
00:06:41.880Well, of course, classical economists operate in la-la land.
00:06:47.040And so, yes, if you had all the time in the world and if you were a very committed calculational machine, then you would sit there and spend 400 years looking at all of the information before you bought that house or purchased that car.
00:07:03.300But we don't do that, rather, what we do is we look at a certain amount of information and at what point we say, I've seen enough, I'm ready to buy that house.
00:07:13.540I've seen enough, I'm ready to buy that Mazda.
00:07:15.380So, what is the mechanism that you use cognitively in your brain so that you could say, I'm now stopping and committing to a choice?
00:07:30.760Now, the reason why the model that I worked on in my doctoral dissertation is called a sequential binary model, it's because what you're basically doing is you are left down to two final choices.
00:07:45.340So, this model kicks in once you've narrowed the field of possible choices down to two.
00:07:51.140So, think, for example, about the presidential elections in the United States.
00:07:55.000There is a primary election process where many candidates might present themselves within their own party.
00:08:03.620Then they whittle it down to one person.
00:09:00.980And then I might have some backups in the top 30, but I'll never look at any business schools that are below top 30 because it's not worth for me to go to that business school then because it's not prestigious enough.
00:09:14.020And so, there is a mechanism by which humans, in general, consumers in particular, will whittle down their choices down to the final two, and that's when my model kicks in.
00:09:24.480So, that's why it's called a sequential binary choice model.
00:09:26.880It is sequential because what you're doing, so now if you look at the first figure or screenshot that I sent you, it's called the criterion-dependent choice model.
00:09:39.720Can I get a thumbs up from somebody just so that I can make sure that you're following me because it's going to make the conversation a lot easier if I can assume that everybody is looking at those curves.
00:09:51.580Can I get a thumbs up from anybody, the criterion-dependent choice model?
00:11:17.800And so, what this model does, this cognitive psychological model, what it does is it exactly explains step-by-step the cognitive processes that your brain goes through in making that stopping decision.
00:11:33.720So, if you see on that curve, there are two horizontal lines that I called K.
00:11:41.560K just means this is the level of differentiation that I must reach in order that I either choose A or B.
00:11:50.840So, if A ever becomes so ahead that it crosses that K curve, I stop and choose A or if in symmetric way, if I get to B first, I stop and choose B.
00:12:04.960So, those are called stopping thresholds because basically what it's saying is,
00:12:09.640I need to achieve that level of differentiation between Mazda and Toyota before I'm sufficiently convinced that I'm ready to choose whatever, whichever car wins first.
00:12:25.620So, what you're going to do is you're going to acquire one piece of attribute at a time across the two alternatives.
00:12:33.240So, let's say my most important attribute is price.
00:12:36.000So, I will look at price of the Mazda and of the Toyota.
00:12:40.840Depending on which one scores higher, there's going to be a tracking curve that either goes up towards the A stopping threshold or the B stopping threshold.
00:18:33.900After three pieces of information, A is ahead at 1.8.
00:18:38.120So, now, A is starting to really differentiate itself.
00:18:42.260But, while it's getting close to the stopping threshold of 2.5, it's not there yet.
00:18:48.340Therefore, my brain is saying, I'm not ready yet to stop.
00:18:51.520I need more differentiation before I choose between Clinton and Trump, between car A and car B, between this university and that university.
00:19:04.480So, now, I'm going to go on to the fourth piece of information, my fourth most important.