Blue-Eyed Players Hit Just Fine in Day Light

Josh Hamilton thinks his eye color is the cause of his hitting problems during day games, and at least one optometrist agrees with him. After initially thinking it was just talk, the idea that there could be some scientific explanation that explained his problems made this story more interesting. So, the next natural step was to look at some data.

On Friday, we asked you guys to come up with blue-eyed players, and you responded with enthusiasm. Over the weekend, I went through that thread and looked at all the nominated players, compiling a list of guys who might make for a useful comparison to Hamilton. I left out players who played a significant part of their career in a dome, for instance, and left out guys who were noted sunglass/tinted contact lens wearers, as we wanted to measure the performance of light eyes in day light with as few compounding factors as possible. Overall, I came up with 25 players who fit the criteria. It doesn’t sound like a huge number, but those guys combined for over 47,000 day-time plate appearances and over 100,000 night time plate appearances in their careers, so sample size shouldn’t be a problem.

The results? Well, you probably won’t be too surprised.

During the evening, these blue-eyed players combined for a career mark of .280/.363/.472. During the day, they hit .282/.364/.475, almost exactly the same as they did when it was dark out. This non-difference matches up with the rest of the population, as there is no consistent historical day/night split for Major League hitters over the years. The sample of blue-eyed players we looked at follows the trend established by the rest of Major League Baseball.

The group split right down the middle, with 13 players posting a higher OPS in the evening and 12 players having a higher OPS in the afternoon. The full list of players and the data can be found here.

Of the guys who hit worse during the day, the biggest differences go to Casey Blake (.688 day OPS, .815 night OPS), Tim Salmon (.836/.900), and Chase Utley (.863/.905). On the other side of things, J.D. Drew (.904/.864), Scott Brosius (.771/.729), and Mark Grace (.844/.804) all had the largest positive day/night splits.

Grace is perhaps one of the most interesting cases, as his eyes are very blue and he spent the majority of his career with the Chicago Cubs, who play more day games than any other franchise in baseball. If having light eye colors led to significant struggles during the day time, Grace should have been the most affected player in baseball. Instead, he thrived during day games. I looked to see if there was any kind of obvious career trend that came from perhaps an adjustment later in his career after his eyes got used to all the day games, but, no, he was a good hitter in the day time even early in his career.

Now, I don’t mean to suggest that the optometrist is a crackpot or that there’s nothing to what Hamilton is saying. Certainly, medical experts know far more about how eyes react to sun light than anyone writing for FanGraphs, and only Hamilton knows exactly what he sees during the day and at night. But history does seem to suggest that if there’s a negative impact on blue-eyed players in day games, previous players have found a way to overcome it without it hindering their performance.

And, from a logical standpoint, that makes sense. Nearly every kid on earth grew up playing exclusively day baseball in Little League, and even at the high school level, almost every game for most teams is played in sun light. Practice is always during the day. The batting cages that took all of our money as kids? Only open during the day time.

Night baseball is the exception until a player becomes a professional. Nearly every player in the big leagues was trained to hit a baseball in sunlight, so those whose eye color really does hinder their ability to hit the ball in day light will likely be weeded out long before they ever make it to the big leagues. The structure of amateur baseball would essentially act as a filter, removing players who can’t see the baseball well in day light.

Maybe Hamilton is the outlier here. Maybe his eyes are especially sensitive, and he’ll sustain a large day/night split going forward. It seems more likely, however, that we’re just looking at noise generated by looking at a sample of fewer than 600 career plate appearances, and Hamilton was looking for a reason to explain something that goes beyond randomness.

He’s not the first blue-eyed player in baseball, and history suggests guys who had similar eye colors have done just fine in day games over the years. The Rangers (and Hamilton) would do well to not spend too much time or effort on fixing this problem – smart money says it will probably just go away on its own.

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Dave is the Managing Editor of FanGraphs.

71 Responses to “Blue-Eyed Players Hit Just Fine in Day Light”

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  1. Pat says:

    I’m glad he made the comments because it lead to some interesting research here.

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  2. Justin Merry says:

    Nice job. I would just say that if Hamilton thinks it is a problem, he should do what he feels is necessary to overcome it–as many players apparently have. The effect on eyes is real from an optics standpoint, but a good pair of polarized sunglasses probably fix the issue…

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    • joser says:

      There’s enough of a mental component to hitting that if he thinks it’s a problem, it’s a problem. Conversely, however, if he happens across something — anything — that seems to fix the problem, it will fix the problem. Even if the original “cause” has no validity and the “solution” (“special” sunglasses? magic eyeblack? Voodoo cystals? pink underwear?) makes no sense. A Placebo is a placebo, but an Effect is still an effect.

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  3. bluejaysstatsgeek says:

    Isn’t it possible that some people are simply more light sensitive than others? While it may correlate somewhat to eye colour, as evidenced by the fact that optometrists routinely advise blue-eyed patients to wear sunglasses during the day, it isn’t a perfect predictor. I believe light sensitivity is as individual as myopic tendencies.

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    • James K. says:

      Yep. Not all people with light-colored eyes are ultra-sensitive to sunlight, but almost all people who are ultra-sensitive to sunlight have light-colored eyes. It’s a little more nuanced than the discussion here and a statement like “Blue-Eyed Players Hit Just Fine In The Daylight” isn’t fair to Hamilton or what he is saying.

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      • Pat says:

        Dave says as much in the article “Maybe Hamilton is the outlier here. Maybe his eyes are especially sensitive, and he’ll sustain a large day/night split going forward.”

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      • Yirmiyahu says:

        There’s nothing wrong with the title. Blue-eyed players, as a group, hit just fine in the daylight. That doesn’t mean that *all* blue-eyed players hit fine in sunlight. And Hamilton was apparently wrong to blame his problems on the simple fact that he has blue eyes. And Dave fully acknowledged, “Maybe his eyes are especially sensitive.”

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      • Brian Williamson says:

        “Almost all people who are ultra-sensitive to sunlight have light-colored eyes”

        Can you divulge your source, or should we take your word for it?

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    • Greg says:

      I agree. I think one of the flaws of some saber people is that they don’t always acknowledge the possibility of outliers and simply dismiss something if it doesn’t hold true for the mean.

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      • Pat says:

        YEAH! You’d wish they’d at least acknowledge such a possibility in their articles, like maybe in the last paragraph as they make their conclusions….. :/

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  4. RotoChamp says:

    Excellent work, Dave. Thanks for following through with the research and preventing a myth from being born.

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  5. Nate says:

    A Different Test

    Find the players with the biggest significant (both in magnitude and sample size) day/night splits. What are their eye colors?

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    • Yirmiyahu says:

      Brown. Because most baseball players have brown eyes.

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      • Michael says:

        I think Dave’s analysis is just fine. However, if someone wanted to undertake Nate’s study, the metric wouldn’t be to analyze the probability of dark/light eyes, since as Yirmiyahu points out the majority will have dark eyes (availability heuristic). The better metric would be how does the distribution of light/dark eyes in this subset compare to the normal distribution.

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      • Blue says:

        Exactly, Michael.

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  6. Mr Punch says:

    Historical note: Blue eyes used to be far more common; a century ago, half of all Americans had blue eyes. The proportion was probably higher among the ethnic groups most represented in major league baseball for most of its history. And these guys played in daylight. If the Hamilton theory were true, we’d have to adjust upward our understanding of just how good players of the past were relative to those of today.

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  7. jason k says:

    Guys who feel like the light effects them will just wear sunglasses, and they will be excluded from your sample. Performance data isn’t really a good way to test Hamilton’s hypothesis.

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    • Telo says:

      This is a very good point. But do many players wear sunglasses when hitting? It’s the kind of thing that I just can’t picture in my head… I know I can’t hit a baseball or golf ball when wearing sunglasses. There’s something about the depth perception that throws you off. I can’t imagine may MLBers do it.

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      • duncanbishop1 says:

        I’ve batted and golfed many times just fine with sunglasses on and haven’t felt any depth perception issues. It may be that I have above average vision, or that I have brown eyes. Just my personal experiences.

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      • david says:

        jeff kent looked like billie jean king in his glasses…or maybe it was the moustache.

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  8. davef says:

    I was really hoping the Grace picture was his recent DUI mugshot.

    What about Cal Ripken? How’d he do?

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  9. Detroit Michael says:

    It seems like the placebo effect is strong enough that it would be buying tinted contacts or something like that for Hamilton. In other words, nice article although I disagree with the last sentence.

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  10. Telo says:

    Now this is what Fangraphs is all about. A question that leads to real original research, and the author leaves us with a clear conclusion.

    Sorry Josh…

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  11. David says:

    Maybe Josh Hamilton is stuck in a self-fulfilling prophecy of terrible hitting during the day. I would imagine there is a certain level of mental midgetry going on in that head of his about this and the media response probably doesn’t help either. I don’t see things getting better for him for a while when it comes to hitting during the day.

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  12. GeneHackman says:

    Maybe he smokes crack during the day?

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  13. j6takish says:

    Also, Hamilton plays in Texas. During July/August it’s still light outside until almost 10pm. Couldn’t this just be a case of a players slumps occurring during the day out of pure random chance?

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    • Cliff says:

      What? Texas is on the southern border of the U.S. It has the least daylight of any state in the union.

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      • joser says:

        Yeah, somebody doesn’t understand obliquity or the solar calendar. Look to Seattle or Toronto in June, not Texas in August.

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  14. Klatz says:

    This is good observational data against Hamilton’s hypothesis. But you’d need to do a more rigorous study to be conclusive.

    There could be selection bias: the blue-eye players who succeeded were the ones who learned to adapt the best, eye-wear issue: the blue-eyed players tend to use eye wear to compensate, etc.

    You’d need to recruit two matched groups (or a two large random groups) and test their eye sight in light/dark conditions.

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    • mk says:

      It definitely occurred to me that when we call out names of blue-eyed players off the top of our heads, we’re likely going to call out memorable folks.

      That’s a list of pretty successful ballplayers, who I’d assume were likely to then have succeeded in most scenarios.

      Be interesting (if time-consuming) to see a list of more bench-type players who had shorter or less successful careers matched up with this…although I guess that’s a selection bias of its own right there.

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  15. geo says:

    You eliminated contact lens wearers…but didn’t you realize that Hamilton himself wears contacts?

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    • Bryz says:

      Dave meant he excluded players that wore tinted contacts.

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    • Bill says:

      Hamilton had never worn contacts before Saturday’s game and wore them for 3 AB’s. His last AB he discarded them and said later he wasn’t gpoing to wear them again.

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  16. Darrell Revok says:

    I admit I’m a horrible person, but I hate Josh Hamilton. The guy is immensely talented, but sure seems to have an excuse for everything. Why celebrate stars who quietly reach their potential like Zimmerman, Braun, Votto etc. when you can celebrate someone who squandered his for so long?

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    • Jacob says:

      What exactly does he have excuses for? Just because he made a mistake doesn’t mean he’s making excuses.

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  17. NSCEGF says:

    Any daytime problems Mark Grace had surely were due to hangovers rather than eye color.

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  18. jscape2000 says:

    From the article:
    “Hamilton said afterward that the contacts did help during batting practice. Manager Ron Washington throws a few batting practice sessions every day and Hamilton said normally he has trouble picking up Washington’s throws because they come at him with the bleachers as the background. But he could see the ball better with the lenses on Friday.”

    The issue seems to be picking up the ball out of the background. While Dave’s work suggests that eye color doesn’t have an overwhelming effect on hitter performance in day and night, the article suggests that the problem is with the quality of the park’s batter’s eye.

    I don’t have a quick check for this other than the team’s day/night home splits. When was the last time the Ballpark at Arlington was renovated?

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  19. ajh says:

    It’s been awhile since I took a stats class, but shouldn’t we compare blue vs brown eyed players in the daytime? If we’re trying to find what effect blue eyes have on the ability to hit during the day, don’t we need to look at what happens to brown eyed players too?

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    • Liem says:

      Dave addressed that issue with this paragraph:

      “During the evening, these blue-eyed players combined for a career mark of .280/.363/.472. During the day, they hit .282/.364/.475, almost exactly the same as they did when it was dark out. This non-difference matches up with the rest of the population, as there is no consistent historical day/night split for Major League hitters over the years. The sample of blue-eyed players we looked at follows the trend established by the rest of Major League Baseball.”

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  20. Spencer says:

    Brown eyes here…and my eyes are extremely light sensitive…

    I also played baseball growing up and struggled mightily in daylight compared to night time. I’m just gonna blame that for why I didn’t make the bigs!

    Out of curiosity, I’d be interested in seeing what % of ML players (also broken down by pitcher or hitter) have blue eyes compared to brown eyes and how that compares to the general population. Ethnicity would have to be taken into account as well. If there is anything to this light sensitivity thing you would see more a higher % of brown eyed players in the bigs…

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    • Will says:

      This is the first thing I thought, too. If there might hypothetically be a filtering process in little league and high school, I’d be interested to see how many people (if any) it filters.

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  21. mcbrown says:

    I think a better way to evaluate the Hamilton Hypothesis would be to look at how blue-eyed players have fared in Arlington during Hamilton’s time in Texas. For an effect like this, I would expect the orientation of the park to make a huge difference. Rangers Ballpark has home plate at the Northwest of the stadium, which probably means the sun in shining more directly into batters’ eyes than it is at say Fenway Park, which has home plate in the Southwest of the stadium. Not to mention the fact that Rangers Ballpark is at a lower latitude than all but ~4 MLB stadiums (just eyeballing it from a map – I could be off by a team or two), which might have a major impact on the orientation of the sun and the intensity of sunlight in the early afternoon.

    In short, I wouldn’t rule out this effect just yet.

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  22. SFSUGatorAlum says:

    Maybe his notorious past has created some issues with his durability and eyesight? He does seem to get injured every year and now he’s the outlier on a vision sample.

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  23. Choo says:

    It’s not the blue eyes. It’s the ginger.

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    • Choo says:

      For example, tOPS+ for Bobby Kielty, aka Ronald McDonald:

      Day – 88
      Night – 106

      Bam, case closed.

      But just for fun, here’s another one. Mark McGwire, aka McGinger:

      Day – whoa, uh . . . never mind! Carry on.

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  24. marshen says:

    Hamilton’s past drug abuse may have had long term effects on his vison (blurred vision) and playing outside all the time in bright sunlight could aggrevate this whether he wears protective lenses or not. It is a possibility.

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  25. jessef says:

    shouldn’t the sampling unit here be the player, not the plate appearance, since the outcome of the plate appearance is not independent of the batter? I guess you could nest plate appearance within each batter and that would be okay.

    Either way, since each batter could be differentially affected by sunlight, I would think what we should be looking for here is whether there is an effect of daylight on the batter, not on the plate appearance. If so, shouldn’t our sample size be 25 and our 47k daytime plate appearances vs. 100k nighttime plate appearances be merely subsamples that we use to estimate how the light affects each player?

    I imagine that your conclusions are correct and, unless Hamilton is an outlier, the daylight is probably not what’s affecting him. Nonetheless, the way the data were analysed, it seems like one player with a lot of day games (i.e., Mark Grace) could be skewing the results.

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  26. TheGrandslamwich says:

    Props to Notgraphs for being the first on this cite to bring this subject to life!

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  27. About all the data proves is that their exists a control group. As to whether Hamilton is exhibiting a real or placebo effect, its not in this data. You may have shown them, but what are Hamilton’s day/night splits historically? However, on the presumption he has this deficiency, I would get over to Southwestern Medical School for a look ASAP.

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  28. Kat says:

    Maybe he has some variation on the Photic sneeze reflex? Apparently this affects 18-35% of the population, and speaking as someone who has it, even if I’m not sneezing, I am sensitive to changes in light levels and it can cause some unpredictable physical reactions. I tend to think that people who are really affected by this reflex would not become baseball players, but maybe there are some.

    Physiology related to vision is interesting.

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  29. Peter says:

    Here’s the real question that no one is asking…
    How does this affect Max Scherzer who has one blue eye and one brown eye?

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  30. Phantom Stranger says:

    The effect may or may not be real, but too small to be shown in the numbers from the limited sample. Literally hundreds of physiology studies have concluded there are real physical performance differences between morning and night people depending on the time of day, so that effect might be masking the smaller blue eye problem. Some players do show consistent night/day splits over their careers. An area of research might focus on the outliers and investigate their backgrounds.

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  31. Anonathan says:

    Not to make it any more complicated, but wouldn’t ballpark geography impact the results? In other words, certain stadiums may be situated in a way that the sun shines in on the hitters more during the afternoon, while others cause the sun to shine on outfielders.

    So perhaps some light-eyed fielders have worse defensive stats during the day in certain ballparks, unless they wear sunglasses in the field, but not at bat . . . .

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  32. iDoc says:

    What really has the most impact on light sensitivity isn’t iris color, but the amount of pigmentation of the Retinal Pigment Epithelium (RPE), a layer of the retina in the back of the eye that absorbs excess light that’s not absorbed by the photoreceptors and prevents light scatter. Just from anecdotal experience, those with blue eyes are most likely to have a lightly pigmented RPE, but not all of them do. In other words, it is very likely that a lot of the blue-eyed players in your study had a normally pigmented RPE and thus weren’t extra sensitive to the daylight.

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  33. Union of Concerned Scientists says:

    I don’t think anything conclusive can be drawn from this exercise, for a variety of reasons. Most importantly, the 25 blue-eyed players measured are, by Cameron’s own definition, major league success stories (accounting for tens of thousands of at bats). Were the daylight to truly affect the hitting of some blue-eyed players, this group Cameron studied would be the one that you would expect to NOT have suffered an affect…if they had, they wouldn’t have been around to amass those plate appearances. Indeed, it appears they conform exactly to the larger population of their successful major league peers.

    I think what you want is a repeated measures study, testing the career arcs of blue vs brown eyed players as they develop through the minors. Or a study of players before the time at which we can confirm they’ve succeeded. Are rookie-ball players that have poor day/night splits more likely to have blue eyes? This would be a better sample population than successful major leaguers.

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  34. Levi Davis says:

    I would love to get Dave’s thoughts on this:

    Really don’t know what to make of any of it just yet.

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  35. As an Ophthalmologist and specialist in vision performance, my facility the Visual Fitness Institute provide services to numerous MLB team. In conjunction with our research partners at Texas A&M Corpus Christi we analyzed data on data on pro ballplayers which included their eye color. Our unpublished findings did not show any correlation between performance and and eye color.

    What every eye doctor knows is that in sunlight that constricts pupils most everyone sees better than at night when pupils are dilated. Its the glare that the culprit whether that be from lack of pigment in the iris or in the retina as described above by IDoc

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  36. Dr. Ben Bloom says:

    Fascinating subject. Fascinating responses. After examining all of them I think that Kat is the closest to the truth. Recent research has shown that there is a group of people who are constitutionally photophobic (sensitive to light). And this group is more likely to suffer from migraines. Even if they do not actually have classic migraine they are thought to be on the migraine spectrum. It would be reasonable to hypothesize that, even if you’re not having headache symptoms, your neurological performance at a highly exacting task (playing baseball) may be slightly impaired in bright light. So, does Josh Hamilton have migraines? Or does a member of his family have migraines? Family history is known to predispose to a migraine tendency.

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  37. Alexandra Liebler says:

    My son is doing a 6th grade science project on this topic so it has become quite interesting to read this thread. I think a very important point Dave makes in his analysis is the following: The structure of amateur baseball would essentially act as a filter, removing players who can’t see the baseball well in day light possibly explaining why he didn’t see much of a diff in his statistical analysis but not dismissing the fact that blue eyed players may be at a disadvantage when hitting in bright sunlight. My husband was a collegiate baseball player with very light blue eyes and he said he never thought about it hindering him vs other players – he just learned to adjust as best he could so you might be right that those that cannot adjust fall out of the system and those that adapt keep moving up. We’ll be doing a test with young kinds in little league to see their daytime vs night hitting performance and review their stats of 2 years of day and night games to see if there is a significant difference. Will let you know.

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  38. Alexandra Liebler says:

    Dave do you have any idea what % of players in MLB are blue eyed? The total population in the US is about 16% – does MLB have a much lower % of blue eyed players than the norm of 16%? That would further support the theory that the blue eyed players are at a disavantage and don’t make it to the big leagues. Those that do except some outliers like Josh have learned to adapt better than others.

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