Dominican Walk Rates over Time - Plate Discipline

Dominican Walk Rates Over Time | FanGraphs Baseball

				Dominican Walk Rates Over Time | FanGraphs Baseball Daily baseball statistical analysis and commentary.
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by Matt Klaassen - October 30, 2012

Excellent article from both Fan Graphs and Baseball Prospectus that demonstrate how the old stereotypes about Latin American hitters may be shifting right before our eyes. 

HIGHLIGHTS FROM THE ARTICLES:

 While raw skills will always be coveted, it's the players who can translate skills into statistical production—the definition of which seems to change every day—who are considered stars. 

In the short term, this deficiency is causing teams to waste valuable developmental time in trying to teach on-base skills and plate discipline to kids who have no concept of what that means or who have grown up believing that watching a pitch pass by is a sin. And in the end, it might be a fruitless cause anyway. 

 The simplest explanation for this endemic lack of discipline is that Dominican kids rarely play games. Socioeconomic conditions have made sports a low government priority in the poverty-stricken country. By the time players are 17, the AL international scouting director estimates, Dominican players are at least 1,000 at-bats behind their American counterparts. 

"There's not a lot of little league baseball," said Brian Mejia, co-founder of the Dominican Prospect League. "There is a lack of structure for organized baseball at that level. Some kids only learn 'see ball, hit ball.' Free swingers are out there because if they don't have a lot of athleticism, they believe that 'I have to hit.' A lot of it is too because so many of those kids suffer from malnutrition that they have to start their swing so early [because they lack the strength to catch up quickly to fastballs]. They are trying to adapt but getting rid of bad habits is difficult."

It's not that Dominicans are less culturally inclined to be patient—a notion so stereotypically ignorant that it's hardly worth mentioning—it's that they simply haven't had the experiences that would teach them to play that way.

The differences in walk rate are more pronounced in the minors, though the gaps don't grow at the lower levels—we see the biggest separation at Triple-A, at least this season.

Something else it's important to note: some players in the "Dominican" group were born in the Dominican Republic but played in the United States as amateurs and were drafted, not signed as international free agents. These players—including Albert Pujols and Jose Bautista—didn't receive the same sort of swing-happy instruction Jorge wrote about, so we checked to make sure that they weren't skewing the results. Take those players out, and we see some slight changes in the Dominican-born (and Dominican-raised) group at the major-league level: swing rate rises from 47.4 percent to 47.8 percent, O_Swing rate rises from 31.3 percent to 31.7 percent, and walk rate falls from 7.0 percent to 6.8 percent.

As expected, the Dominican-born, U.S.-raised players in the sample weren't saddled with the same impatient approach.

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Dominican Walk Rates Over Time | FanGraphs Baseball

				Dominican Walk Rates Over Time | FanGraphs Baseball Daily baseball statistical analysis and commentary.
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by Matt Klaassen - October 30, 2012

Last week, Jorge Arangure wrote a nice piece on the lack of plate patience among Dominican hitters. The article was helpful in illustrating the conditions that reinforce the oft-cited Dominican baseball adage that "you can't walk off of the island." It also inspired me to take a little look at the historical numbers among Dominican-born players to see if there's been any change in walk rates over the years.

Ben Lindbergh wrote a helpful companion piece running some plate-discipline-related numbers for Dominican players in 2012. What I wanted to examine, though, was if anything changed over the years, and to speculate what might have caused the change.

In comparing the walk rates of Dominican major-league hitters relative to everyone else, I ran into one obvious problem: the initial sample was incredibly small. Back in 1956, Dominican-born hitters had 12 plate appearances in the major leagues, all from the Giants' Ozzie Virgil, Sr., the first Dominican to play in the majors (incidentally, in 1958, he was traded to Detroit and broke the color barrier for the Tigers). Virgil also was the full sample (241 plate appearances) of Dominican hitters in 1957. In 1958, there were two Dominican-born hitters in the majors, but in 1959, it was one again. In 1960, there were four Dominican hitters in the league.

Without going year-by-year, you get the idea: early on, the samples were very small. I try not to give the illusion that I am terribly sophisticated statistically, so, somewhat arbitrarily, I  began with 1964. That's the first season in which at least 10 Dominican-born hitters (I excluded pitchers' hitting from this study) got plate appearances in the major leagues. Still, even 10 players is a very small sample. That was about 2.7% of all major league plate appearances by non-pitchers in 1964 — up from about 1.5% the previous season. We have to start somewhere, though. There has been a general increase in numbers of Dominican-born players and plate appearances by them since then.

While a numbers of things make up a good plate approach, for the sake of simplicity and sticking with the overall tenor of discussions around this issue, I restricted the survey to walk rate. Here is a graph of the walk rates of Dominican-born hitters since 1964, compared to non-Dominican-born hitters:

While both lines have fluctuations, the overall trend is pretty clear: the walk rate for Dominican-born hitters has been catching up to that of non-Dominicans. Comparing the walk rates of 1964 and 2012, the non-Dominican walk rate is almost the same; it has increased by 0.6%. The walk rate of Dominican-born hitters, in contrast, is about 48% higher in 2012 than in 1964.

By itself, of course, this does not tell us much. Many things have changed since Ozzie Virgil's debut. The number of Dominicans in the majors leagues and major-league presence there and elsewhere internationally is obviously far greater now than it was 50 years ago. In 1964, only 10 non-pitcher Dominicans got major-league plate appearances. By the early '00s, the seasonal number is more than 50 — usually around 10% of plate appearances by non-pitchers. That in itself is enough to indicate great changes that would have far-reaching effects. Which of those are most germane with respect to walk rates. That is something for a future piece. There are a number of factors that would have to be considered. Here is a short list of possible considerations. It is not meant to be exhaustive, nor are these possibilities mutually exclusive.

*Qualification: This search is based on the easily-available criterion of birthplace, so the grouping is done by whether a player is born in the Dominican Republic. However, the issue of Arangure's piece is Dominican youth baseball culture, not birthplace. That is not to say that birthplace is not a decent stand-in for a quick query like this, but it's simply to note that there is a difference. Players such as Manny Ramirez and Jose Bautista were born in the Dominican but, in Ramirez's case, he grew up in the United States.; in Bautista's case, he went to college in the U.S. They did not have a traditional route for Dominican players. I don't think it makes the graph useless, but it's worth noting that it might skew things given the issue of Arangure's piece was early baseball instruction in the Dominican Republic. One cause of the increase on the chart might be that more Domican-born players are being raised in the U.S.

*One obvious hypothesis for the improvement might be that Dominican baseball instruction is more friendly to walks than before. This might be the case, although the tone of Arangure's piece tends to make it seem otherwise. Morever, there are other possibilities.

*Remember that this survey is just of those Dominican-born players who actually make the majors. Increased major-league attention to Latin America in the past half-century has likely enabled them to scout and select Dominican players with better plate approaches.

*Along the same lines, there might be better minor-league instruction generally, and/or for Dominican players specifically.

To repeat, these are just some suggestions that are neither exhaustive nor exclusive. One thing is clear, though: whatever they were taught as youngsters, those Dominican hitters who make the major leagues have been catching up with the rest of the league in their ability to draw walks. The reasons why are matters for further research.

Baseball Prospectus | Baseball ProGUESTus: Finding a Way to Walk off the Island

				Baseball Prospectus | Baseball ProGUESTus: Finding a Wa... Are Dominican hitters hurting themselves by focusing on raw skills at the expense of a patient approach? And can anything be done about it?
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Finding a Way to Walk off the Island

by Jorge Arangure Jr.

Most of our writers didn't enter the world sporting an @baseballprospectus.com address; with a few exceptions, they started out somewhere else. In an effort to up your reading pleasure while tipping our caps to some of the most illuminating work being done elsewhere on the internet, we'll be yielding the stage once a week to the best and brightest baseball writers, researchers and thinkers from outside of the BP umbrella. If you'd like to nominate a guest contributor (including yourself), please drop us a line.

Jorge Arangure has been a baseball writer since 2003. He has worked as a senior writer for ESPN and The Washington Post. He's got #want and is #wet and will probably spend his BP freelancing money drinking with Jason Parks.

Two years ago, during a lull in an often sloppily played Dominican Prospect League game being contested at a team academy on the outskirts of San Pedro de Macoris, an independent trainer conspicuously called to a player in the batter's box in the middle of an at-bat. After a pitch had thudded into the catcher's glove, the boy, aged 15 and frail, turned quickly and stepped out of the batter's box. 

"Stop looking at pitches," the trainer said angrily. "Swing the bat."

The boy nodded and continued his at-bat, which concluded with a groundout to shortstop. 

Games of this sort, played by unsigned prospects, have become commonplace in a country that is trying to narrow a learning gap that has become exposed as the game continues to shift toward more nuanced baseball skills. While raw skills will always be coveted, it's the players who can translate skills into statistical production—the definition of which seems to change every day—who are considered stars. 

These games, and to an extent Dominican Summer League games, are fascinating character studies. Since no fans are allowed into the academies, the majority of observers are either coaches, scouts or trainers, which creates a highly pressurized environment for kids aged anywhere from 14-17. Prospects can hear every word shouted to them, and all of these instructions hold special resonance since they are uttered by men who control their young futures. 

Kids will listen to what these men say, and follow their instruction. Unfortunately, much of what these young players are hearing—like the trainer chastising his prodigy for being selective—is steering them astray. 

It's been more than a decade since the value of on-base percentage reached the mainstream, yet the significance of that has yet to hit the island. While the industry has evolved to evaluate players based on advanced metrics that capture the impact of previously overlooked contributions, scouting and teaching in the Dominican continues to be based on raw skills grounded in flawed fundamentals. 

Put simply, among other things, Dominican players don't walk. Some stunning number to consider: out of the top 10 leaders in walks last year in each of the 10 full-season minor leagues, only four of the possible 100 players were Dominican. Only two undrafted, non-U.S.-educated, Dominican-born players rank in the top 40 in baseball in walk rate since 2009: David Ortiz, and Cleveland's Carlos Santana. 

In the short term, this deficiency is causing teams to waste valuable developmental time in trying to teach on-base skills and plate discipline to kids who have no concept of what that means or who have grown up believing that watching a pitch pass by is a sin. And in the end, it might be a fruitless cause anyway. 

"I think you can help a kid, but I don't think you can change a kid from what he is," said one American League international scouting director. "You're not turning someone like Vladdy (Vladimir Guerrero) into a disciplined hitter." 

Mark Newman, a Yankees senior vice president, believes that with hard work—usually during periods such as the instructional league, which will take place for most organizations in the next month or so—a team could significantly improve the walk rate of approximately 10-15 percent of players, a number that hardly seems encouraging. In that example, only one out of 10 offensive players signed out of the Dominican will ever acquire the secondary skills that would make him a very valuable hitter in the majors.

Dominican youngsters are trading potentially lucrative long-term contracts as professionals for the quick profit they can turn by exhibiting skills that will get them a signing bonus as amateurs. Only one of the 30 biggest contracts ever handed out was given to a Dominican-born, amateur free agent player: Alfonso Soriano. And the biggest reason why the Soriano contract has turned into such a disaster for the Cubs? While Soriano can hit (he has 372 career home runs), he can't walk (a lowly .323 career OBP and 7.2 percent walk rate). 

The simplest explanation for this endemic lack of discipline is that Dominican kids rarely play games. Socioeconomic conditions have made sports a low government priority in the poverty-stricken country. By the time players are 17, the AL international scouting director estimates, Dominican players are at least 1,000 at-bats behind their American counterparts. 

"There's not a lot of little league baseball," said Brian Mejia, co-founder of the Dominican Prospect League. "There is a lack of structure for organized baseball at that level. Some kids only learn 'see ball, hit ball.' Free swingers are out there because if they don't have a lot of athleticism, they believe that 'I have to hit.' A lot of it is too because so many of those kids suffer from malnutrition that they have to start their swing so early [because they lack the strength to catch up quickly to fastballs]. They are trying to adapt but getting rid of bad habits is difficult."

Mejia estimates that about 60 percent of prospects in the DPL are playing organized baseball for the first time. Players who don't play baseball as children usually lack a basic understanding of baseball's more mental skills: baserunning, plate discipline, etc. 

It's not that Dominicans are less culturally inclined to be patient—a notion so stereotypically ignorant that it's hardly worth mentioning—it's that they simply haven't had the experiences that would teach them to play that way. 

But with amateur signing bonuses now being capped by baseball's new rules regarding international free agents, there is no better time to shift thinking toward more advanced methods of instruction.

If they don't adapt, Dominican players face a future in which an industry de-values them and limits the length of their careers as they climb up baseball's organizational ladder. The older these players get, and the more they lose their raw athletic skills (bat speed, running speed, hand speed, etc), the easier it will be for them to be replaced by the next crop of young, fundamentally flawed Dominicans. 

***

Baseball Prospectus | BP Unfiltered: Dominican Players and Plate Discipline: Additional Data

				Baseball Prospectus | BP Unfiltered: Dominican Players a... How does the plate discipline of Dominican players compare to the league as a whole?
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Dominican Players and Plate Discipline: Additional Data

by Ben Lindbergh

If you read Jorge Arangure Jr.'s great guest piece on Dominican players and plate discipline today, you may have wondered, as I did, whether we could see any difference between Dominicans and non-Dominicans in the data. Jorge mentioned how few Dominicans are among their respective leagues' leaders in walk rate, but I wanted to see how DR-born players stacked up as a group. I asked BP data dude Dan Turkenkopf to run the numbers, and this is what he found for major leaguers in 2012. (Note: pitcher hitting is included, and the "league" rates include Dominican players.)

	Pitches	Swing Rate	O_Swing_Rate	UIBB Rate
League	695953	46.0	29.2	7.4
Dominican	68823	47.4	31.3	7.0

Major leaguers born in the Dominican Republic did swing and chase slightly more often and walk slightly less often in 2012 (which doesn't mean they were worse hitters overall). Of course, there could be some selection bias here, since Dominican players with worse plate discipline than Angel Berroa would be weeded out before they make the majors. We don't have plate discipline stats for minor leaguers, but we can check their unintentional walk rates:

Level	LG_PA	LG_UIBBR	DO_PA	DO_UIBBR	DIFF
MLB	184179	7.4%	18547	7.0%	0.4%
Triple-A	164927	8.4%	12369	5.8%	2.6%
Double-A	158288	8.6%	14860	6.5%	2.1%
A Adv. (Full Season)	156140	8.2%	15508	6.4%	1.9%
A (Full Season)	158317	8.6%	18018	7.0%	1.6%
A (Short Season)	63737	8.6%	9606	6.4%	2.2%
Rookie	79243	8.6%	12741	7.1%	1.4%

The differences in walk rate are more pronounced in the minors, though the gaps don't grow at the lower levels—we see the biggest separation at Triple-A, at least this season.

Something else it's important to note: some players in the "Dominican" group were born in the Dominican Republic but played in the United States as amateurs and were drafted, not signed as international free agents. These players—including Albert Pujols and Jose Bautista—didn't receive the same sort of swing-happy instruction Jorge wrote about, so we checked to make sure that they weren't skewing the results. Take those players out, and we see some slight changes in the Dominican-born (and Dominican-raised) group at the major-league level: swing rate rises from 47.4 percent to 47.8 percent, O_Swing rate rises from 31.3 percent to 31.7 percent, and walk rate falls from 7.0 percent to 6.8 percent.

As expected, the Dominican-born, U.S.-raised players in the sample weren't saddled with the same impatient approach.

Your Big Doubts About the 10,000 Hour Rule Are Well-Founded | Library of Economics and Liberty

Great stuff on the Nature versus Nurture debate, the Ten Thousand Hour Rule and more from what may seem like an unlikely source, the Library of Economics and Liberty. BTW this site and this article demonstrates my theory that you can judge a site by the quality of the comments in the comments section and this site is top notch, top quality and first class all the way. Therefore, it is appropriately bookmarked and highly recommended.


Your Big Doubts About the 10,000 Hour Rule Are Well-Founded | EconLog | Library of Economics and Liberty

				Your Big Doubts About the 10,000 Hour Rule Are Well-F... Ericsson, Krampe, and Tesch-Romer's
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Ericsson, Krampe, and Tesch-Romer's "The Role of Deliberate Practice in the Acquisition of Expert Performance" (PSYCHOLOGICAL Review 1993) isn't just one of the most famous articles in the history of academic PSYCHOLOGY.  Thanks to Malcolm Gladwell's Outliers, the article's bullet points are now famous around the globe.  It is from this article and related RESEARCH the Gladwell distills his "10,000 Hour Rule."

What does the 10,000 Hour Rule really say?  A few caveats aside, the Rule says that 10,000 hours of deliberate practice is both necessary and sufficient for world-class expertise.  Listen, for example, to Gladwell talk about musical expertise.

The striking thing about Ericsson's study is that he and his colleagues couldn't find any "naturals," musicians who floated effortlessly to the top while practicing a fraction of the time their peers did. Nor could they find any "grinds," people who worked harder than everyone else, yet just didn't have what it takes to break the top ranks. Their research suggests that once a musician has enough ability to get into a top MUSIC SCHOOL, the thing that distinguishes one performer from another is how hard he or she works. That's it. And what's more, the people at the very top don't work just harder or even much harder than everyone else. They work much, much harder.

This may seem like journalistic hyperbole, but it's quite close to the original RESEARCH.  Ericsson, Krampe, and Tesch-Romer:

Contrary to the popular "talent" view that asserts that differences in practice and experience cannot account for differences in expert performance, we have shown that the amount of a specific type of activity (deliberate practice) is consistently correlated with a wide range of performance including expert-level performance, when appropriate developmental differences (age) are controlled. Because of the high costs to the individuals and their environments of engaging in high levels of deliberate practice and the overlap in characteristics of deliberate practice and other known effective training situations, one can infer that high levels of deliberate practice arenecessary to attain expert level performance. Our theoretical framework can also provide a sufficient account of the major facts about the NATURE and scarcity of exceptional performance. [emphasis mine]

And:

We attribute the dramatic differences in performance between experts and amateurs-novices to similarly large differences in the recorded amounts of deliberate practice. Furthermore, we can account for stable individual differences in performance among individuals actively involved in deliberate practice with reference to the monotonic relation between accumulated amount of deliberate practice and current level of performance.

Although I've found great value in Ericsson's research, his skepticism about innate talent always struck me as crazy.  Yes, experts energetically hone their crafts.  But everywhere I look, I see Gladwell's "naturals" - people who are good despite relatively little time investment - and "grinds" - people who are mediocre despite massive time investment.  Only recently, though, did I discover a pile of researchthat confirms my big doubts about the 10,000 Hour Rule.  Highlights of the highlights:

More than 20 years ago, researchers proposed that individual differences in performance in such domains as music, sports, and games largely reflect individual differences in amount of deliberate practice, which was defined as engagement in structured activities created specifically to improve performance in a domain. This view is a frequent topic of popular science writing--but is IT SUPPORTED by empirical evidence? To answer this question, we conducted a meta-analysis covering all major domains in which deliberate practice has been investigated. We found that deliberate practice explained 26% of the variance in performance for games, 21% for music, 18% for sports, 4% for education, and less than 1% for professions. We conclude that deliberate practice is important, but not as important as has been argued.

The case of chess:

On average, deliberate practice explained 34% of the reliable variance in chess performance, leaving 66% unexplained and potentially explainable by other factors. We conclude that deliberate practice is not sufficient to account for individual differences in chess performance. The implication of this conclusion is that some people require much less deliberate practice than other people to reach an elite level of performance in chess. We illustrate this point in Fig. 2 using Gobet and Campitelli's (2007) chess SAMPLE, with the 90 players classified based on their chess ratings as "master" (≥2200, n = 16), "expert" (≥2000, n = 31), or "intermediate" (<2000, n = 43). There were large differences in mean amount of deliberate practice across the skill groups: master M = 10,530 h (SD = 7414), expert M = 5673 h (SD = 4654), and intermediate M = 3179 h (SD = 4615). However, as the SDs suggest, there were very large ranges of deliberate practice within skill groups. For example, the range for the masters was 832 to 24,284 h--a difference of nearly three orders of magnitude. Furthermore, there was overlap in distributions between skill groups. For example, of the 16 masters, 31.3% (n = 5) had less deliberate practice than the mean of the expert group, one skill level down, and 12.5% (n = 2) had less deliberate practice than the mean of the intermediate group, two skill levels down. In the other direction, of the 31 intermediates, 25.8% (n = 8) had more deliberate practice than the mean of the expert group, one skill level up, and 12.9% (n = 4) had more deliberate practice than the mean of the master group, two skill levels up.

The figure:

The case of music:

On average across studies, deliberate practice explained about 30% of the reliable variance in music performance, leaving about 70% unexplained and potentially explainable by other factors. We conclude that deliberate practice is not sufficient to account for individual differences in music performance. Results of other studies provide further support for this conclusion. Simonton (1991) found a large amount of variability in the amount of time it took famous classical composers to have their first "hit," and that the interval between the first composition and the first hit correlated significantly and negatively with maximum annual output, lifetime productivity, and posthumous reputation. Composers who rose to fame quickly-the most "talented"-had the most successful careers. Furthermore, Sloboda, Davidson, Howe, and Moore (1996) noted that although students at a selective MUSIC SCHOOL ("high achievers") had accumulated more "formal practice" than students who were learning an instrument at a non-music school ("pleasure players"), there were some individuals at each skill level (grade) who did "less than 20 per cent of the mean amount of practice for that grade" and others who did "over four times as much practice than average to attain a given grade" (p. 301).

If deliberate practice doesn't explain everything, what does?  Lots of stuff.  Starting age.  IQ. PERSONALITY.  Specific cognitive skills, too.  Consider working memory:

Ericsson and colleagues have argued that measures of working memory capacity themselves reflect acquired skills (Ericsson & Delaney, 1999; Ericsson & Kintsch, 1995), but working memory capacity and deliberate practice correlated near zero in this STUDY (r = .003). There was also no evidence for a Deliberate Practice × Working Memory Capacity interaction, indicating that working memory capacity was no less important a predictor of performance for pianists with thousands of hours of deliberate practice than it was for beginners.  

Fortunately, we can salvage most of the original RESEARCH behind the 10,000 Hour Rule.  Instead of thinking of 10,000 hours of deliberate practice as a mandatory minimum for expertise, take it as a rule of thumb: On average, a world-class expert has to practice for about 10,000 hours to reach the top.  Instead of thinking of 10,000 hours as a guarantee of expertise, adopt a pluralistic and probabilistic approach: 10,000 hours combined with lots of innate talent will usuallytake you to the top.

Most importantly, though, think of deliberate practice as a general THEORY ofimprovement, not a special THEORY of expertise!  Some people learn more much easily than others.  But almost anyone can improve in almost anything.  How?  By deliberately practicing the specific skills they wish to improve.  RESEARCH on deliberate practice doesn't undermine intelligence research by showing that genius is a myth.  Instead it reinforces Transfer of Learning research by showing that learning is highly specific.

HT: GMU econ prodigy Nathaniel Bechhofer

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Science aid: Nature versus Nurture

				Science aid: Nature versus Nurture Is intelligence caused by nature (genetics) or nurture (how you are raised/the environment)? Look at twin, adoption and selective breeding studies to com...
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Nature versus Nurture

In this article we will be exploring the age-old nature or nurture debate: which is more relevant; your genes or how you are bought up. This particular article will be concerned with inteligence.

Evolution and Genetics

Firstly, what is evolution? It is a process where the creatures that are best adapted to survive will live longer and therefore be able to reproduce more and have a greater number of offspring. Many of these offspring will have this characteristic and over the course of many generations all in that species will have this characteristic.

It can be defined briefly as: a gradual change in a species over time because of a natural selection of the best adapted to an environment.

Now we move on to a simple look at genetics. As you know, we have genes which give us different characteristics and these genes are inherited from our parents. The actualgenetic code is known as the genotype. However, you get one gene from each parent for everything, but obviously only one of these can be expressed; so how the genes actaully manifest themselves is called the phenotype.

Twin Studies

A twin study is one of the method used. There are two types of twin: dizygotic (DZ) who are regular fraternal twins; and then monozygotic (MZ) which are identical twins and so have exactly the same DNA as each other, i.e. the genotypes are identical. The table below summarizes what the various findings would mean.

In particular it is useful to look at MZ twins (since there genetics are the same) who have been raised together or apart. This was done by Shields (1962), and found the correlation between inteligences of MZ growing up together was 0.83 and growing up apart was 0.51. This would appear to show the environment is more important, however there are some methodological issues related to this study.

A correlation shows how two things are related, but don't give a definite reason. Also, it is only recently that we can prove two twins are identical, it could be that DZ twins that looked very similar were included because they thought they were identical. And finally there is the issue of what was counted as 'seperated' in the study, some twins were included who were raised but different family members but lived near to each other, regually saw each other and went to the same school.

............

Conclusion

Very sorry to dissappoint you, but the conclusion is that both nature and nurture play an important role, however perhaps that the environment is the deciding factor.

The idea used to describe it is the Rubber Band Hypothesis. It says that the potential (length of the band) is decided by genetics. However the environment stretches this band, so that someone with a low potential could be stretched beyond someone with a high because of environmental differences. However if someone with a high and someone with a lower genetic potential had the same environment, that person with the higher genetic potential would be able to 'stretch' their intelligence to a higher level.