WEBVTT - SYMHC Classics: John Dalton 0:00:02.440 --> 0:00:07.320 Cappy Saturday. John Dalton was born on September fifth or sixth, 0:00:07.600 --> 0:00:10.479 seventeen sixty six or two hundred and fifty nine years 0:00:10.520 --> 0:00:15.280 ago today or possibly yesterday on the day this episode 0:00:15.320 --> 0:00:19.160 is coming out. John Dalton was a physicist and a chemist, 0:00:19.239 --> 0:00:23.400 but he's also known for his discoveries related to color 0:00:23.520 --> 0:00:28.120 vision and color vision anomalies. Our episode on John Dalton 0:00:28.280 --> 0:00:31.200 is Today's Saturday Classic, and it originally came out on 0:00:31.320 --> 0:00:38.040 January twentieth, twenty twenty one. Enjoy Welcome to Stuff You 0:00:38.040 --> 0:00:48.120 Missed in History Class, a production of iHeartRadio. Hello, and 0:00:48.159 --> 0:00:53.000 welcome to the podcast. I'm Holly Frye and I'm Tracy V. Wilson. Tracy, 0:00:53.120 --> 0:00:55.760 I bet this happened to you. I know it happened 0:00:55.800 --> 0:00:58.319 to me. Like you must have had those moments as 0:00:58.320 --> 0:01:00.520 a child where you thought you were being very insightful. 0:01:00.560 --> 0:01:02.480 I know I certainly did where I was like, how 0:01:02.520 --> 0:01:04.559 do I know that what I see is the same 0:01:04.600 --> 0:01:08.840 thing as other people see? I had this exact Yes. Yes, 0:01:08.959 --> 0:01:11.240 I also asked my mom one time. I was like, Mom, 0:01:11.280 --> 0:01:15.040 how do we know that what I see as green 0:01:15.400 --> 0:01:18.000 is the same thing as what you see as green? 0:01:19.520 --> 0:01:23.240 And my mom stay at home mom with two little 0:01:23.319 --> 0:01:25.440 children did not always have a lot of patience for 0:01:25.560 --> 0:01:33.480 weird questions. And she was like, it's the same. I'm 0:01:33.480 --> 0:01:35.600 not trying to drag my mom in any way. My 0:01:35.680 --> 0:01:40.480 mom was like of our creativity and attentive to art. 0:01:40.600 --> 0:01:42.360 But yeah, this was a case where I liked I 0:01:42.400 --> 0:01:44.600 just asked her in a question she was not prepared 0:01:44.640 --> 0:01:48.840 for question time. Here is the thing. I asked the 0:01:48.920 --> 0:01:53.520 same question of my father, who I did not know, 0:01:54.880 --> 0:01:56.919 and I don't know that he knew at the time, 0:01:57.600 --> 0:02:04.240 did not see color the way, so he was trying 0:02:04.280 --> 0:02:07.000 to describe things. And I just remember, I mean, I 0:02:07.040 --> 0:02:09.160 was probably like seven or eight, already kind of a 0:02:09.160 --> 0:02:11.080 smart alec and I was just like, okay, this is 0:02:11.120 --> 0:02:13.480 going nowhere. I'm out. So maybe just saying green is 0:02:13.520 --> 0:02:16.000 green was a really a better route because that led 0:02:16.040 --> 0:02:19.080 to a lot of confusion in our lives for a 0:02:19.120 --> 0:02:22.520 moment until we finally put the pieces together right, And 0:02:22.560 --> 0:02:24.600 really what happened was that. And I don't mean to 0:02:24.680 --> 0:02:27.919 drag my father, but like he was career military, so 0:02:28.639 --> 0:02:31.720 he's now retired, but his clothes were like sort of 0:02:31.760 --> 0:02:37.799 prescribed for sure. When he stopped being constantly on active 0:02:37.919 --> 0:02:40.720 duty and started picking out his own clothes. So things 0:02:40.760 --> 0:02:45.959 became readily apparent, which is that that does not go together. 0:02:46.120 --> 0:02:49.640 My dude, Yes, they look they're practically the same color. Oh, 0:02:49.760 --> 0:02:54.000 we should address this, right. That's we never knew for years, 0:02:54.280 --> 0:02:57.400 when you're wearing like jeans and a plaid shirt in 0:02:57.440 --> 0:02:59.240 your off time and then a uniform the rest of 0:02:59.240 --> 0:03:03.200 the time, it would never come up. Now we learned. 0:03:03.960 --> 0:03:06.480 But this curiosity about whether other people see the way 0:03:06.520 --> 0:03:09.440 that you see is really what drives a lot of 0:03:09.480 --> 0:03:12.960 scientific discovery. And we are talking about somebody who was 0:03:13.080 --> 0:03:16.240 curious and did a lot of scientific discovery. But in 0:03:16.280 --> 0:03:19.799 the case of this subject, who was very well known 0:03:19.800 --> 0:03:22.799 and respected in his day, he just didn't think about 0:03:22.840 --> 0:03:26.080 how he or anyone else saw color until he kind 0:03:26.120 --> 0:03:30.040 of stumbled into it while studying plants and realizing that 0:03:30.200 --> 0:03:32.760 his vision might be different from other people. And that's 0:03:32.840 --> 0:03:36.160 John Dalton, And really John Dalton is far more famous 0:03:36.200 --> 0:03:39.320 for his work in atomic theory, which builds the foundations 0:03:39.360 --> 0:03:43.360 of organic chemistry, but he also wrote one of the 0:03:43.400 --> 0:03:47.320 first really thorough descriptions of what he called anomalist's vision, 0:03:47.720 --> 0:03:50.640 meaning that he realized he was not perceiving color in 0:03:50.680 --> 0:03:53.400 the same way as other people, and his descriptions are 0:03:53.600 --> 0:03:56.400 very entertaining. We're going to read some of them, so 0:03:56.440 --> 0:03:58.680 today we will talk a little bit about his life, 0:03:59.240 --> 0:04:03.680 but mostly about this sort of pocket in his scientific work, 0:04:03.960 --> 0:04:06.560 where he made a brief foray into exploring the world 0:04:06.600 --> 0:04:09.920 of photoreceptors and color perception, although he didn't use those 0:04:09.960 --> 0:04:13.720 words for it. Color blindness is a term that's falling 0:04:13.720 --> 0:04:17.640 out of favor because it's not really accurate. Colorblind suggests 0:04:17.640 --> 0:04:20.679 that somebody can't see color at all, but most people 0:04:20.760 --> 0:04:25.080 who have historically been diagnosed with color blindness can see colors, 0:04:25.080 --> 0:04:28.960 they just see them differently. So defective color vision or 0:04:29.080 --> 0:04:34.320 color vision deficiency are becoming more preferred terms. I feel 0:04:34.320 --> 0:04:38.320 like I see people describing themselves as colorblind still quite 0:04:38.360 --> 0:04:41.320 a lot. So this is something that's evolving. We're still 0:04:41.400 --> 0:04:44.240 kind of at the beginning of the scientific community shifting 0:04:44.320 --> 0:04:48.520 to these different terms, and it's really about clarity more 0:04:48.560 --> 0:04:52.279 than anything else, right, like, no, you do see color. 0:04:52.279 --> 0:04:55.760 We'll talk about one exception, but just differently, So we 0:04:55.839 --> 0:04:58.640 need to make a clearer term for it that's not misleading. 0:04:59.480 --> 0:05:03.680 And color vision deficiency is the inability to distinguish specific 0:05:03.720 --> 0:05:07.599 colors red, green, and blue, and to be diagnosed as 0:05:07.680 --> 0:05:11.599 colorblind historically or color vision deficient. Now, a person only 0:05:11.640 --> 0:05:15.160 needs to have an inability to distinguish one of these colors, 0:05:15.600 --> 0:05:17.960 but it is possible for someone who has color vision 0:05:17.960 --> 0:05:22.000 deficiency to be unable to distinguish all three. So in 0:05:22.200 --> 0:05:26.440 your retina, you have cells called rods, which perceive light, 0:05:26.680 --> 0:05:30.320 and then three types of cells called cones. Cones are 0:05:30.320 --> 0:05:34.000 really the important factor here. They are the photoreceptive cells 0:05:34.040 --> 0:05:37.760 that enable us to perceive color. The human retina contains 0:05:37.800 --> 0:05:42.839 six million cones. Red sensing cones make up sixty percent 0:05:42.920 --> 0:05:47.240 of the total number of cone cells, green sensing cones 0:05:47.279 --> 0:05:50.320 make up thirty percent, and blue sensing tones make up 0:05:50.520 --> 0:05:53.400 the remaining ten percent. So if all of your cone 0:05:53.400 --> 0:05:56.560 cells are functioning normally, you are said to have trichromacy, 0:05:56.960 --> 0:06:00.240 meaning you can see three try of these colors. They 0:06:00.240 --> 0:06:04.359 combine to create standard vision. But it is also possible 0:06:04.400 --> 0:06:07.320 to have dichromasy with only two types of cone cells 0:06:07.360 --> 0:06:11.440 present or functioning, or even monochromacy where only one type 0:06:11.440 --> 0:06:14.800 of cone is functioning. Monochromacy is a little bit tricky 0:06:14.839 --> 0:06:17.360 because it can also be used to describe a scenario 0:06:17.480 --> 0:06:20.520 where none of a person's cones are functioning, and a 0:06:20.560 --> 0:06:23.880 person who has monochromacy may have other vision issues as well, 0:06:24.080 --> 0:06:26.919 And monochromacy that we just talked about with no cone 0:06:26.960 --> 0:06:29.800 function is kind of the one variation in all of 0:06:29.800 --> 0:06:33.279 this where the color blind label would be actually pretty accurate, 0:06:33.360 --> 0:06:37.320 because everything to them appears not in the rainbow of colors, 0:06:37.320 --> 0:06:39.880 but as a shade of gray most of the time. 0:06:40.000 --> 0:06:43.520 Dichromacy manifests itself in a way that a person can't 0:06:43.560 --> 0:06:48.440 see a difference between red and green, and dichromacy of 0:06:48.480 --> 0:06:51.919 this nature is broken down into separate classifications based on 0:06:52.160 --> 0:06:54.839 which types of cones do and don't work in a 0:06:54.880 --> 0:06:59.360 person's retina. Protonopia describes a state of not being able 0:06:59.400 --> 0:07:02.360 to see red, and due to anopia is a case 0:07:02.400 --> 0:07:05.919 where the red cones function but the green cones do not. 0:07:06.680 --> 0:07:09.760 Blue yellow color deficiency, which is a little rarer, is 0:07:09.840 --> 0:07:13.560 similarly broken down into classifications based on its specific nature 0:07:13.600 --> 0:07:16.200 in a given person. So someone with a lack of 0:07:16.280 --> 0:07:19.160 blue cones is said to have tritonopia, and if they 0:07:19.160 --> 0:07:22.280 have blue cones but reduce sensitivity to that color, it 0:07:22.360 --> 0:07:26.880 is actually described as tritinomaly. An all color vision deficiency 0:07:26.960 --> 0:07:30.080 can fall on a spectrum. Some people have a diminished 0:07:30.120 --> 0:07:34.000 ability to distinguish red from green, for example, but they're 0:07:34.080 --> 0:07:38.920 able to see difference within specific shades of these colors. Yeah. 0:07:38.920 --> 0:07:41.280 Sometimes you know, people can't hit the lighter tones of 0:07:41.320 --> 0:07:43.720 the darker tones get real muddy, but they can see 0:07:43.920 --> 0:07:47.720 different shades. It's all. It manifests in many different ways, 0:07:48.320 --> 0:07:50.920 and in the United States an estimated five to ten 0:07:51.000 --> 0:07:55.160 percent of the population have some form of color vision deficiency. 0:07:55.960 --> 0:07:59.040 Usually this gets tested for when people are kids, and 0:07:59.120 --> 0:08:02.760 more boys than girls have colored vision deficiency, and the 0:08:02.760 --> 0:08:05.960 percentage shifts based on race. So there was a twenty 0:08:06.000 --> 0:08:09.200 fourteen study that gets cited a lot. This was published 0:08:09.200 --> 0:08:12.960 in the journal Optthalmology, and it had taken studies of 0:08:13.040 --> 0:08:16.880 the color vision of four thousand California children ranging in 0:08:16.920 --> 0:08:20.040 age from three to six. And in this study it 0:08:20.080 --> 0:08:22.360 was found that among the girls, less than half a 0:08:22.400 --> 0:08:25.920 percent of them exhibited signs of color vision deficiency, regardless 0:08:25.920 --> 0:08:29.520 of race, but in boys the numbers were different. Six 0:08:29.600 --> 0:08:32.200 percent of the white boys in the study were diagnosed 0:08:32.200 --> 0:08:35.760 with color vision deficiency, three percent of the Asian boys 0:08:35.800 --> 0:08:39.000 had some form of color vision deficiency. It was found 0:08:39.040 --> 0:08:41.640 in fewer than three percent of the Latino boys and 0:08:41.720 --> 0:08:46.120 less than two percent of Black boys. Genetically, boys are 0:08:46.200 --> 0:08:50.120 more likely to have red green color vision deficiency because 0:08:50.160 --> 0:08:53.760 they only need to inherit it from their mother. It 0:08:53.800 --> 0:08:58.920 is a recessive characteristic that's associated with the X chromosome. 0:08:59.600 --> 0:09:04.199 So if a female inherits the trait from her mother 0:09:04.360 --> 0:09:08.080 but not her father, she'll generally have normal color vision 0:09:08.880 --> 0:09:12.880 she only has that one X chromosome, but then she 0:09:12.880 --> 0:09:15.400 could pass the trait onto her own children. And this 0:09:15.520 --> 0:09:18.720 is different from blue yellow color vision deficiency, which is 0:09:18.720 --> 0:09:21.360 a dominant characteristic, and so that only needs to be 0:09:21.400 --> 0:09:24.760 inherited from one parent, and it is not linked to 0:09:24.800 --> 0:09:29.199 a person's sex. I'm just gonna say these are related 0:09:29.240 --> 0:09:34.320 to sex and not to gender. That's the different thing. Yeah, 0:09:34.400 --> 0:09:37.120 we're going with kind of that twenty fourteen studies Separation 0:09:37.200 --> 0:09:40.079 of Boys and Girls, which simplifies the whole discussion, and 0:09:40.200 --> 0:09:45.520 is sex assigned at births not necessarily? How if they 0:09:45.520 --> 0:09:47.480 did that, I would be fascinated if they did the 0:09:47.520 --> 0:09:50.360 same exact test today and how they would break it out, 0:09:50.440 --> 0:09:54.240 because it's things have shifted a bit. So if anybody 0:09:54.280 --> 0:09:56.440 knows of any studies similar to that going on today, 0:09:56.600 --> 0:09:59.920 I'm very curious. But here's the thing. You're probably wonder 0:10:00.120 --> 0:10:02.559 how we figured all of this out. And in the 0:10:02.640 --> 0:10:06.480 late eighteenth century, this idea of people perceiving color differently 0:10:06.720 --> 0:10:10.640 than most humans was certainly not unknown. King George the Third, 0:10:10.679 --> 0:10:15.120 for example, reportedly discussed this with an English novelist, Fanny Burney, 0:10:15.200 --> 0:10:18.480 at court in seventeen eighty five, and there were some 0:10:18.600 --> 0:10:22.319 theories about what caused color vision anomalies published in Germany 0:10:22.360 --> 0:10:25.800 in the late seventeen hundreds, but the first systematic analysis 0:10:25.840 --> 0:10:29.160 of color vision deficiency appears in seventeen ninety three, at 0:10:29.200 --> 0:10:31.440 least the first that we know of, and that brings 0:10:31.520 --> 0:10:33.240 us to the person we mentioned at the top of 0:10:33.240 --> 0:10:36.720 the show, John Dalton. John Dalton was born in early 0:10:36.760 --> 0:10:40.560 September seventeen sixty six. His actual date of birth is 0:10:40.600 --> 0:10:45.560 either September fifth or September sixth. His parents, Joseph Dalton 0:10:45.720 --> 0:10:49.120 and Deborah green Up Dalton, were Quakers. His father made 0:10:49.160 --> 0:10:52.240 a living as a weaver. The Dalton's had three children 0:10:52.280 --> 0:10:55.599 who lived to adulthood, and John was the youngest of them, 0:10:55.800 --> 0:10:59.240 and as a child, John attended a Quaker school and 0:10:59.320 --> 0:11:02.960 that school chain hands. When John was twelve, John Fletcher, 0:11:03.000 --> 0:11:05.160 the man who had been running it, gave it to 0:11:05.280 --> 0:11:09.200 John Dalton's older brother, Jonathan Dalton, and then Jonathan enlisted 0:11:09.240 --> 0:11:12.520 John's assistance in this new role, and this set John 0:11:12.559 --> 0:11:15.600 on a path as an educator. Just kind of delights 0:11:15.640 --> 0:11:20.000 me that they had a John and a Jonathan. It 0:11:20.040 --> 0:11:23.520 makes me giggle as well. John and Jonathan expanded their 0:11:23.559 --> 0:11:26.600 new careers by taking over a school in Kendall, England, 0:11:26.720 --> 0:11:30.559 when John was just fourteen. This was a larger operation 0:11:30.840 --> 0:11:33.360 than the Quaker grammar school they had been running, and 0:11:33.400 --> 0:11:36.360 it included students who boarded as well as day students. 0:11:36.640 --> 0:11:40.839 That's totaled about five dozen students in all. And John 0:11:40.960 --> 0:11:43.200 was sort of learning on the job. He was studying 0:11:43.200 --> 0:11:46.520 with scholars to learn math, Latin, Greek and science to 0:11:46.679 --> 0:11:48.960 stay ahead of his students and to be able to 0:11:48.960 --> 0:11:52.640 speak on the subjects of their curriculum. And keep in mind, 0:11:52.679 --> 0:11:57.080 again he's like fourteen fifteen at this fight, so he 0:11:57.160 --> 0:11:59.959 is taking in a lot of information. And he stayed 0:12:00.160 --> 0:12:02.040 in that job for a dozen years and then at 0:12:02.040 --> 0:12:04.640 the age of twenty seven, John moved on to a 0:12:04.679 --> 0:12:08.000 new professional post as a mathematics teacher at New College, 0:12:08.000 --> 0:12:10.640 and this was in Manchester. And he found all this 0:12:10.720 --> 0:12:13.520 a little bit frustrating though, because his workload in that 0:12:13.679 --> 0:12:16.680 job prevented him from having time to pursue his own 0:12:16.720 --> 0:12:20.640 scientific study. So he switched gears and decided that he 0:12:20.640 --> 0:12:23.120 would become a private tutor so that he could manage 0:12:23.120 --> 0:12:25.360 his own time in a way that would enable him 0:12:25.400 --> 0:12:28.200 to carry on with his side work. At this point, 0:12:28.200 --> 0:12:31.400 his work outside of his daily teaching task was focused 0:12:31.480 --> 0:12:35.000 largely on meteorology. He had been publishing articles in the 0:12:35.040 --> 0:12:38.920 subject for several years, but he kept studying other sciences 0:12:38.960 --> 0:12:42.480 as well, and it was through these studies that he 0:12:42.520 --> 0:12:45.480 wound up writing a paper that expounded on the idea 0:12:45.640 --> 0:12:49.560 that not everyone saw colors in the same way. So 0:12:49.840 --> 0:12:52.360 this was not the first time the mention of non 0:12:52.360 --> 0:12:56.360 standard color vision appeared in print. As we said earlier, surely, 0:12:56.440 --> 0:12:59.439 color vision diviiciency has been in play almost as long 0:12:59.440 --> 0:13:02.680 as humans have existed, and even before Dalton there had 0:13:02.760 --> 0:13:06.080 been some mentions of it, including a write up of 0:13:06.120 --> 0:13:09.040 a man named Thomas Harris that was published in Philosophical 0:13:09.040 --> 0:13:14.199 Transactions and that described Harris's Inability to Distinguish Colors, which 0:13:14.440 --> 0:13:17.400 was published in seventeen seventy seven. We're going to come 0:13:17.400 --> 0:13:20.240 back to Harris and we'll talk first more about John Dalton. 0:13:20.440 --> 0:13:21.880 But before we do all of that, we're going to 0:13:21.960 --> 0:13:34.640 pause for a brief sponsor break. John Dalton presented his paper, 0:13:34.720 --> 0:13:37.559 which was titled Extraordinary Facts relating to the Vision of 0:13:37.640 --> 0:13:42.280 Colors with Observations by Mister John Dalton, at Manchester's Literary 0:13:42.320 --> 0:13:46.240 and Philosophical Society on October thirty first, seventeen ninety four. 0:13:47.000 --> 0:13:50.360 He had joined the Society upon moving to Manchester. And 0:13:50.440 --> 0:13:53.000 as scientific papers go, this one is kind of unique 0:13:53.040 --> 0:13:55.880 in that Dalton himself is really the subject of the paper, 0:13:56.000 --> 0:14:00.000 or at least his vision was. That text opens with quote, 0:14:00.360 --> 0:14:04.760 it has been observed that our ideas of colors, sounds, tastes, 0:14:04.960 --> 0:14:09.280 et cetera, excited by the same object, may be very 0:14:09.320 --> 0:14:12.760 different in themselves without our being aware of it. He 0:14:12.840 --> 0:14:15.800 goes on quote I was always of the opinion, though 0:14:15.840 --> 0:14:19.080 I might not often mention it, that several colors were 0:14:19.280 --> 0:14:24.440 injudiciously named. The term pink in reference to the flower 0:14:24.520 --> 0:14:28.080 of that name seemed proper enough. But when the term 0:14:28.320 --> 0:14:32.120 red was substituted for pink. I thought it highly improper. 0:14:32.280 --> 0:14:35.680 It should have been blue in my apprehension, as pink 0:14:35.760 --> 0:14:39.960 and blue appear to me very nearly allied, whilst pink 0:14:40.000 --> 0:14:45.600 and red have scarcely any relation. He goes on in 0:14:45.640 --> 0:14:48.400 his introduction to mention how he had learned about light 0:14:48.440 --> 0:14:51.200 and optics in his scientific studies, but he hadn't really 0:14:51.200 --> 0:14:54.800 thought about applying any of that information to colors because 0:14:54.840 --> 0:14:58.000 that entire area, the idea of color, seemed kind of 0:14:58.040 --> 0:15:00.120 confused and odd to them. Like he really was, like, 0:15:00.120 --> 0:15:02.200 why would people group these colors together? It doesn't make 0:15:02.200 --> 0:15:05.560 any sense, But I guess that's how we've always done it. 0:15:05.560 --> 0:15:08.400 It was not until he turned his scientific work to 0:15:08.440 --> 0:15:11.840 botany that he really started thinking about why some color 0:15:11.880 --> 0:15:15.720 groupings just made no sense. And this study prompted him 0:15:15.720 --> 0:15:19.440 to ask other people questions about colors. He actually uses 0:15:19.480 --> 0:15:22.840 the example in this paper of asking a person whether 0:15:22.880 --> 0:15:26.000 a flower was blue or pink. But they always just 0:15:26.040 --> 0:15:28.480 thought he must be joking because the queries came off 0:15:28.480 --> 0:15:31.040 as so completely absurd to them. So he just thought 0:15:31.120 --> 0:15:35.520 everybody had this weird relationship with color, even though he 0:15:35.600 --> 0:15:38.840 thought colors made no sense. It didn't really occur to 0:15:38.920 --> 0:15:42.240 him to wonder if there was something unusual about the 0:15:42.240 --> 0:15:45.960 way he was perceiving colors. It was a moment in 0:15:46.080 --> 0:15:49.760 seventeen ninety two, two years before he presented his paper, 0:15:49.760 --> 0:15:53.160 that really gave him this moment of pause. That moment 0:15:53.400 --> 0:15:57.400 happened when he was looking at a geranium by candlelight. 0:15:57.920 --> 0:16:00.720 So he had frequently seen these flowers in this particular 0:16:00.880 --> 0:16:04.480 variety he was looking at were in fact pink in daylight, 0:16:04.760 --> 0:16:07.960 and to him, in daylight he perceived them as sky blue. 0:16:08.480 --> 0:16:12.080 But by candlelight, he saw this flower as a vibrant red, 0:16:12.680 --> 0:16:15.400 And this significant shift in their color due to lighting 0:16:15.480 --> 0:16:19.560 changes startled him and led him to make a quick 0:16:19.600 --> 0:16:22.080 study by asking a number of friends to look at 0:16:22.120 --> 0:16:26.120 these same flowers in both daylight and candlelight. All the 0:16:26.160 --> 0:16:28.520 people he initially asked about it saw them as pink 0:16:28.640 --> 0:16:32.800 in both lighting conditions, except for his brother, who perceived 0:16:32.880 --> 0:16:35.240 that same shift of them being sky blue in the 0:16:35.320 --> 0:16:39.160 day and red in candle light. This experience caused him 0:16:39.160 --> 0:16:42.280 to start a more structured study of light and color, 0:16:42.720 --> 0:16:45.560 which he did with an assistant who had quote normal 0:16:45.680 --> 0:16:50.040 color vision. First, he used a prism to project sunlight 0:16:50.080 --> 0:16:52.680 into a dark room and then recorded the number of 0:16:52.760 --> 0:16:55.440 colors that various people saw in that band of light. 0:16:55.600 --> 0:16:59.640 Most of them saw six red, orange, yellow, green, blue, 0:16:59.680 --> 0:17:03.320 and pearl. He does mention that purple is separated into 0:17:03.360 --> 0:17:07.960 indigo in violet in Newton's writings on color for the 0:17:07.960 --> 0:17:11.160 purposes of a person simply looking at a band of light, 0:17:11.640 --> 0:17:14.640 that distinction is really nominal. I think we talked about 0:17:14.640 --> 0:17:17.000 this in one of our episodes that touched on Newton previously. 0:17:17.160 --> 0:17:19.560 He put indigo and violet in there separately because he 0:17:19.600 --> 0:17:24.160 wanted there to be seven. So that's why people typically 0:17:24.160 --> 0:17:27.040 don't actually see them as two estate shades in light 0:17:27.080 --> 0:17:30.680 from a prism. Yeah, or you'll see what you think 0:17:30.800 --> 0:17:34.200 is maybe a slight difference, but it's hard to be sure. Yeah, 0:17:34.640 --> 0:17:38.520 So for Dalton, he just called that one thing, it's purple. 0:17:39.320 --> 0:17:41.880 When Dalton looked at the prismatic light, though, he could 0:17:41.880 --> 0:17:46.920 only make out two or sometimes three colors, so generally 0:17:46.960 --> 0:17:50.080 he just saw yellow and blue, or sometimes he would 0:17:50.080 --> 0:17:53.639 see yellow, blue and a little bit of purple. And 0:17:53.720 --> 0:17:55.959 through his work he identified that the band that he 0:17:56.040 --> 0:17:59.439 saw as yellow was where other people were seeing red, orange, yellow, 0:17:59.480 --> 0:18:02.720 and green, and he wrote quote that part of the image, 0:18:02.760 --> 0:18:05.600 which others call red, appears to me little more than 0:18:05.600 --> 0:18:10.000 a shade or a defect of light. After that, the orange, yellow, 0:18:10.040 --> 0:18:13.680 and green seem one color which descends pretty uniformly from 0:18:13.720 --> 0:18:17.000 an intense to a rare yellow, making what I should 0:18:17.000 --> 0:18:20.719 call different shades of yellow. Dalton's perception of blue and 0:18:20.800 --> 0:18:23.960 purple aligned with what other people were seeing, and the 0:18:24.040 --> 0:18:27.280 contrast between the end of his band of yellow and 0:18:27.320 --> 0:18:30.760 the adjacent blue was really sharp. So next he did 0:18:30.800 --> 0:18:34.640 the same collecting of perceptions from himself and others when 0:18:34.680 --> 0:18:38.240 looking at candle light projected through a prism, and these 0:18:38.240 --> 0:18:41.760 results were mostly the same. The only exception that Dalton 0:18:41.840 --> 0:18:44.159 calls out is that for him, the red edge of 0:18:44.200 --> 0:18:47.080 the image looks more vivid in candle light than it 0:18:47.160 --> 0:18:50.560 did looking at sunlight under the same conditions of being 0:18:50.600 --> 0:18:54.280 put through a prism. Dalton's paper next breaks out studies 0:18:54.280 --> 0:18:58.080 of specific colors as he had always perceived them. He 0:18:58.359 --> 0:19:01.640 starts out by describing color grouped with red as they 0:19:01.640 --> 0:19:05.760 appear in the daylight versus candlelight. His description of Crimson 0:19:05.840 --> 0:19:09.800 is pretty charming. Quote Crimson has a grave appearance, being 0:19:09.880 --> 0:19:15.159 the reverse of every showy and splendid color. A similarly 0:19:15.320 --> 0:19:18.600 quaint description is his description of pink. He breaks that 0:19:18.720 --> 0:19:22.080 down as nine parts light blue and one part red 0:19:22.240 --> 0:19:26.119 quote or some other color which has no other effect 0:19:26.240 --> 0:19:29.200 than to make the light blue appear dull and faded 0:19:29.240 --> 0:19:32.520 a little. He also lists out all the flowers that 0:19:32.600 --> 0:19:35.080 to him look blue to give the reader a sense 0:19:35.119 --> 0:19:38.080 of context. When he says he says pinks and reds 0:19:38.160 --> 0:19:41.720 as blue, blood, he says appears to him as the 0:19:41.760 --> 0:19:45.159 color most people call bottle green, and he mentions that 0:19:45.240 --> 0:19:48.720 if he saw a light colored stocking that was spattered 0:19:48.720 --> 0:19:52.280 with either fresh blood or dirt, he would not be 0:19:52.320 --> 0:19:56.920 able to tell the difference visually. I love this entire 0:19:57.000 --> 0:20:00.359 paper so much. It's exactly like this the whole way through. 0:20:01.480 --> 0:20:04.760 His turn of phrase is quite quite charming and endearing. 0:20:05.520 --> 0:20:08.359 He goes on to describe the significant change that red 0:20:08.480 --> 0:20:11.480 undergoes for him when viewed in candlelight. He describes it 0:20:11.520 --> 0:20:14.000 as much more vivid, and the blue no longer being 0:20:14.040 --> 0:20:18.480 present and instead replaced by yellow tones. While he found 0:20:18.680 --> 0:20:22.359 most reds and pinks quite drowned by daylight, in candlelight, 0:20:22.440 --> 0:20:26.479 they became really vivid and even exciting. Orange and yellow, 0:20:26.520 --> 0:20:29.320 he says, are not too different for him than anyone else. 0:20:29.880 --> 0:20:33.159 When he moves on to discussing green, he writes, quote, 0:20:33.200 --> 0:20:37.600 I take my standard idea from grass. This appears to 0:20:37.640 --> 0:20:40.439 me very little different from red. The face of a 0:20:40.560 --> 0:20:43.359 laurel leaf is a good match to a stick of 0:20:43.520 --> 0:20:47.320 sealing wax. Hence, it will be immediately concluded that I 0:20:47.400 --> 0:20:51.960 see either red or green, or both different from other people. 0:20:52.560 --> 0:20:55.480 The fact is I believe that they both appear different 0:20:55.560 --> 0:20:59.400 to me from what they do to others. He concludes 0:20:59.440 --> 0:21:02.439 that blue he generally sees the same as other people, 0:21:02.560 --> 0:21:05.040 and purple is just a little bit different from blue. 0:21:05.840 --> 0:21:08.879 He described brown in the same creative way that he 0:21:08.920 --> 0:21:12.359 does other colors, writing quote, my idea of brown I 0:21:12.400 --> 0:21:16.080 obtain from a piece of white paper heated almost to ignition. 0:21:16.960 --> 0:21:20.439 He also notes that seeing colors in moonlight presents the 0:21:20.480 --> 0:21:23.160 same or near same results for him as seeing them 0:21:23.200 --> 0:21:27.600 in candlelight. Lightning gives the same effect as daylight. It 0:21:27.680 --> 0:21:31.000 doesn't matter whether the sun is rising or setting when 0:21:31.000 --> 0:21:34.879 it comes to color, and any kind of combustible substance 0:21:34.960 --> 0:21:38.960 creates the same color perception as any other flame. He 0:21:39.040 --> 0:21:41.639 concludes the section of the paper with quote, my vision 0:21:41.680 --> 0:21:45.159 has always been as it is now. His next section 0:21:45.359 --> 0:21:48.560 breaks out the information that he's collected from other people 0:21:48.680 --> 0:21:51.800 and their perceptions of color, starting with people he has 0:21:51.840 --> 0:21:54.720 found who have vision that seems similar to his own, 0:21:55.359 --> 0:21:59.240 and Dalton mentions mister Harris of Maryport and his alternate 0:21:59.280 --> 0:22:03.639 perceptions of color. Dalton thought that, based on the description, 0:22:03.960 --> 0:22:07.720 Harris's anomalist's vision might have been different from his own. 0:22:08.520 --> 0:22:11.400 He discovered that one of Harris's brothers was still alive, 0:22:11.480 --> 0:22:15.040 so he made contact and went to visit. Upon questioning 0:22:15.080 --> 0:22:18.320 this brother and testing his vision, Dalton found that the 0:22:18.400 --> 0:22:21.760 Harris family seemed to have the same genetic variable that 0:22:21.840 --> 0:22:24.520 he and his brother had when it came to how 0:22:24.560 --> 0:22:27.400 they perceived the colors of the world around them. This 0:22:27.520 --> 0:22:30.240 led to a general line of questioning of the students 0:22:30.240 --> 0:22:33.480 and colleagues that Dalton regularly came in contact with kind 0:22:33.480 --> 0:22:36.000 of as a subject group, and he found a small 0:22:36.040 --> 0:22:39.720 proportion of them shared his specific experience regarding pink and 0:22:39.800 --> 0:22:43.119 light blue looking similar by daylight and different by candlelight. 0:22:44.040 --> 0:22:47.080 Dalton also found just a couple of examples of people 0:22:47.080 --> 0:22:50.439 who quote differ from the generality and from us, also 0:22:51.119 --> 0:22:53.359 meaning that they seemed to have a different type of 0:22:53.400 --> 0:22:57.760 color vision deficiency. He also mentioned a shared experience among 0:22:57.920 --> 0:23:00.560 all of these people that just as with him, it 0:23:00.680 --> 0:23:02.880 had not occurred to them that they were seeing things 0:23:02.920 --> 0:23:05.800 differently from the majority of people, but that they too 0:23:05.920 --> 0:23:09.320 found the names and groupings of colors perplexing at times. 0:23:09.640 --> 0:23:13.360 Though his paper was really the beginning of science's study 0:23:13.400 --> 0:23:17.720 of color vision deficiency, even in his really relatively small 0:23:17.800 --> 0:23:21.320 data set, Dalton was already capturing information that showed a 0:23:21.359 --> 0:23:25.600 difference in instances of color vision deficiency in regards to 0:23:25.640 --> 0:23:29.320 people's sex. He noted that in the Harris family, four 0:23:29.359 --> 0:23:32.280 of six sons in the family had what would come 0:23:32.320 --> 0:23:35.600 to be known as color vision deficiency, sometimes also called 0:23:35.800 --> 0:23:40.960 Daltonism for obvious reasons, but their sister didn't. Similarly, Dalton 0:23:40.960 --> 0:23:43.960 and his brother Jonathan had the same color experience, but 0:23:44.119 --> 0:23:47.760 their sister did not. He wrote, quote, it is remarkable 0:23:47.840 --> 0:23:50.320