Heredity, Environment,

and School

Achievement

Johnny is brighter than Billy. Heseems to learn more easily, he doesbetter in school, and he scores higheron tests of ability and school achieve-ment. A natural response to such aneveryday observation is to ask, “Whattreatment has Johnny hadthat Billyhas missed? Perhaps if we give Billythese advantages his behavior will be-come more like Johnny’s.” This samecomparison is frequently made betweenstudents in different school systems, dif-

ferentracial or ethnic groups, different

states and different countries; with thesame natural desire to reduce the differ-ences by giving to the poorer the ad-

vantages of the superior.The differences between some of

these groups are fairly large—for ex-ample, 3.7 per cent of high schooljuniors in Connecticut score highenough on a test of educational de-

Robert C. Nichols is Vice President ofResearch at the National Merit Scholar-

ship Corporation, Evanston, Illinois. This

paper was presented as part of a sym-

posium, “Heredity and Environment: Re-newed Examination of an Old Topic,” at

the American Educational Research As-

sociation Meetings, New York City, Febru-

ary 16, 1967.

ROBERT C. NICHOLS

velopment to be commended in theNational Merit program while only0.6 per cent of the students in Arkan-sas score at this level (National MeritScholarship Corporation, 1965). If wecould just find out what it is aboutliving in Connecticut that makes stu-dents so smart, and if we could giveitto the students in the rest of the coun-try, we could more than double thenation’s supply of high level talent.This is certainly a worthwhile goal tostrive for, but where do westart? Thereare a lot of nice things about Con-necticut that might serve as clues. Forexample, in Connecticut there are 242cars per square mile spewing carbonmonoxide andother noxious gases intothe atmosphere while in Arkansasthere are only 12 cars per square mile.This finding cross-validates nicely—forexample, Massachusetts, another state

with a high proportion of able stu-dents, has 230 cars per square milewhile Alabama, another state relative-ly lacking in talented students, hasonly 25 cars per square mile.

I bring up the automobile examplenot just to be funny butalso to illus-trate that ecological correlations canarise in such indirect ways that theyoffer only vague clues that need to be

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checked out with other evidence. Con-necticut and Massachusetts also havehigher teacher salaries and spend moreper student for school facilities thando Arkansas and Alabama, but thisdoesn’t necessarily mean that increas-ing school expenditures will increasestudent performance. We need to lookfor other supporting evidence and forother rival hypotheses to explain theobserved variations in ability.There are three main factors or

types of variables that seem likely tohave an important influence on abil-ity and school achievement. These are(a) the school factor or organized edu-cational influences; (b) the familyfactor orall of the social influences offamily life on a child; and (c) thegenetic factor. In addition to thesethree main factors one might also addnutritional factors, community influ-ences, and so on. According to thecommon sense methodology of firstidentifying factors responsible for theperformance of superior individuals,then giving these advantages to every-one, thereby reducing individual dif-ferences, our first task is to determinethe extent to which individual differ-ences in ability are due to differencesin the major factors or types of in-fluences. This will help us knowwhere to look when wetry to isolatethe particularly salient events thatare responsible for individual differ-ences and to understand the mecha-nisms involved. When we look at thetask from this long-term perspective, itis evident that we have a long way togo.

The separation of the effects of themajor types of influences has proved

to be extraordinarily difficult, and allof the research so far has not resultedin a clear-cut conclusion. If we wereto poll a representative group of edu-cational research specialists concern-ing their best guess as to which ofthe three types of influence just men-tioned—the school factor, the familyfactor, and the genetic factor—is re-

sponsible for the largest proportionof individual differences in, say, verbalability among high school students inthe United States, such a poll wouldnot even give a plurality of the votesto onefactor overthe other two.This messy situation is due primar-

ily to the fact that in human societyall good things tend to go together. Themost intelligent parents—those withthe best genetic potential—also tendto provide the most comfortable andintellectually stimulating home envi-ronments for their children, and also

tend to send their children to the mostaffluent and well-equipped schools.Thus, the ubiquitous correlation be-tween family socio-economic status andschool achievement is ambiguous inmeaning, and isolating the indepen-dent contribution of the factors in-volved is difficult. However, thestrong emotionally motivated attitudesand vested interests in this area havealso tended to inhibit the sort of dis-passionate, objective evaluation of theavailable evidence that is necessary for

the advance ofscience.

THE SCHOOL FACTOR

It seems almost self-evident thatthere should bea large schooleffect onmeasures of ability and academic

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achievement. Universal education inthe United States has obviously beenlargely responsible for producing thehighly literate and capable popula-tion we see today, and without con-tinued educational efforts we wouldundoubtedly regress to more primi-tive levels. But the very fact that edu-cation is so widespread and so obvi-ously successful may reduce its impor-tance as a source of individual differ-ences in ability in this country. It maybe that educators, rightly concernedwith improving the resources withwhich they work, tend to exaggeratethe importance of relatively minor dif-ferences in educational facilities andto forget how hard it is to improve on“Mark Hopkins on one end of a logand the student on the other.” Thusit is legitimate to ask to what extentindividual differences in ability in thiscountry are due to differences in edu-cational experiences without question-ing the importance of the educationaleffort for the population as a whole.

Recentstudies of school effects haveshown a rather monotonous tendencyto find that differences in school ex-periences have little relationship todifferences in student performance aft-er all the relevant background fac-tors have been controlled. This issurprising because improving studentperformance is the main purpose ofthe schools andit stands to reason thatschools with more resources should doa better job than schools with less re-sources. When Sandy Astin and I firststarted our studies of college effectswe expected to find large differencesin the effects of different colleges andwe were very concerned with develop-

ing adequate controls for student in-put so that these effects would showup. But the more we controlled forstudent input the smaller the differ-ences between the graduates at differ-ent colleges became. After failing tofind substantial differential college ef-fects on such variables as Obtaining aPhD. (Astin, 1962), Graduate RecordExamination Score (Nichols, 1964),Career Choice (Astin, 1965), and

Personality Inventory Scores (Nichols,1967), we have mow become con-cerned with how to keep from partial-ling out whatever small differentialcollege effects there may be along withthe much larger differences in studentinput.One might say, as we did after the

fact, that large school effects should

not be expected for college-age stu-dents. By the time a person is 17 yearsold, the major influences have alreadybeen operating for a long time, andthe students have likely developed de-fenses against noxious stimuli andmethods of compensating for environ-mental inadequacies. It seems reason-

able to assume that we will have tolook to earlier ages for substantialschooleffects.

Therecent study of Equality of Edu-cational Opportunity by the US.Office of Education (Coleman,etal.,1966; Nichols, 1966)—the well known

Coleman report—focused on the pe-riod from the first through twelfthgrade, where school effects might more

reasonably be expected. Yet the datafrom this large study led the authorsto conclude the following: “Variationsin school quality are not highly relatedto variations in achievement of pu-

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pils.... The school appears unable toexert independent influences to makeachievement less dependent on thechild’s background” (p. 297). Thus,the same rationalization of negativeresults that we used for colleges is alsoused here—the really formative influ-ences have already taken place; en-during individual differences in abil-ity are already established before stu-dents enterfirst grade.

I expect this sort of reasoning wasone of the major justifications for theHead Start program. Since compensa-tory education programs for older dis-advantaged students did not in gen-

eral result in dramatic improvementsin performance, it seemed reasonableto introduce a pre-school program toreach the children in the formativeperiod before the maladaptive behay-ior patterns had become solidified.Studies of the results of the HeadStart experience suggest that the gainsfrom this program may be temporary

and that the head start tends to belost in a few months (Wolf & Stein,1966). Again, an educational experi-ence does not seem to produce endur-

ing individual differences in abilityand our attention is directed towardeven earlier events.

In the United States where some

sort of education is available to every-one and the mass media continually

bombard us with seductive conceptualmaterial—in other words, where very

few suffer really drastic educationaldisadvantage—the largely negative re-

sults of studies of school effects sug-gest that the family factor and the

genetic factor are likely the major

sources of individual differences inability.

CRITICAL EARLY EXPERIENCES

Perhaps the best evidence for theimportance of early experience forlater intellectual development comesfrom studies of animals. Hebb (1949)has found that animals reared in astimulus-rich environment show en-during superiority in adaptive re-sponse over genetically equivalent an-imals that were deprived of theearly stimulation. Even very brief han-dling experiences of infant mice, ifthey occur at fairly sharply definedcritical periods, will have pronounced

effects on the animals’ reaction tostress for the rest of their lives. Denen-berg is transplanting fertilized ovafrom one strain of mouse to anotherand is finding that some factors thathad previously been thought to begenetic are actually dependent on theintra-uterine environment (personalcommunication, but see Denenberg,1966).

The human situation is undoubted-ly much more complicated than that ofrats and mice, and it is dangerous togeneralize more than the gross prin-ciple that early experience can be veryinfluential on later behavior, and per-

haps that there are critical periodswhen certain experiences are moresalient than atother times.We have very little information

about what early experiences are criti-cal in human development. This is afield that deserves much more atten-tion than it has received, and it willundoubtedly be better worked in the

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future as educational efforts are di-rected at everearlier age levels.

THE FAMILY FACTOR

Oneclue to the importance of a par-ticular configuration of early experi-ences comes from studies of the ef-fects of birth-order, which has recent-

ly become a popular area of research(Altus, 1966). Birth order is a partic-ularly felicitous variable, since validinformation aboutit is easily obtainedat almost any age, and it reveals agreat deal about the early life of theperson. For example, from observingmy own children it is obvious that thefamily experience of the older of twobrothers who are two years apart inage is quite different from the experi-ence of the younger. We became in-terested in this problem when we no-ticed that the talented students in theMerit Program tended to be the

first-born in their families. Typicalfindings are shown in Table 1. AmongMerit Finalists from two-child fam-ilies there are about twice as manyfirst-born as second-born. In three-child families there are about as many

TABLE 1

first-born as second- and third-borncombined, and the second-born out-number the third-born. The sametrend holds true for four- and five-child families. We have come to thinkof this birth-order effect in talentedstudents as an established fact, sinceTerman (1925) also found it in hisgifted group and it holds in five dif-ferent large groups of Merit partici-pants. The same predominance ofear-ly-born children was observed in agroup of 600 talented Negro students(Roberts & Nichols, 1966).There are three possible explana-

tions for these findings: (a) somephysiological effects of the more diffi-cult birth or younger age of the moth-er of earlier-born children may influ-ence intelligence, (b) the differentialfamily environmentof early- andlater-born children may affect the develop-ment of intelligence, or (c) the rela-tionship may be an artifact of varyingbirth rates, differential participationin scholarship programs, or some otherspurious influence.To study these problems we asked

the 800,000 students who took the

Percentage of Merit Finalists Selected in 1964 in Each Birth Position for Two-,Three-, Four-, and Five-Child Families

Number of

Children in Number of Birth Position Chi-Family Finalists I 2 3 4 5 Square

2 568 66 34 60.90°3 414 52 31 17 7959°

4 244 59 21 12 8 159.65*

5 85 52 22 9 ll 6 60.10*

*p<.00l

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NMSQTin 1965 to indicate the num-ber, age, and sex of their siblings.These data allowed us to study therelationship of the test score to birth-order, sex of sibling, and spacing.The results (as yet unpublished)

confirmed the findings concerningbirth-order among Merit Finalists. Theearlier-born the students were in theirfamily, the higher their average testscore; andthis relationship held for allfamily sizes for both boys and girlsregardless of the sex or spacing of thesiblings. For a given family size andbirth-order, the sex of the sibling hadlittle relationship to the test score foreither boys orgirls, but spacing of thesiblings was quite important. The closerin age the nearest sibling, the lower thetest score tended to be; and this ten-dency was more pronounced if the sib-ling was older than if he was younger.The relationship between birth-

order andtest score among all partici-Pants in our screening test seems toindicate that the excess of early-bornamong Merit Finalists is not an arti-fact of greater participation of theolder children in a family or of varyingbirth rates; and the relationship ofsibling spacing to test score seems to

favor a psychological rather than aphysiological explanation for thebirth-order findings.The available data offer no hint as

to whether it is the greater parentalattention often devoted to the first-born children in a family, the compe-titive interaction between thesiblings

themselves or some other factor in thesituation that puts the younger sib-ling at a developmental disadvantage.However; the birth-order findings do

provide an exciting clue to the greatmystery of intellectual development.The mean difference between olderand younger children in closely spacedfamilies is almost as large as the dif-ference between the students in Con-necticut and those in Arkansas. So,if we could discover what makes theolder siblings so smart and give it tothe youngersiblings, the result for thepopulation as a whole would not benegligible.Another example of the sort of evi-

dence that points to the importance ofearly experience for the developmentof intelligence is the study by Wolf(1965) of specific early environmen-tal experiences and later achievement.He reasoned that if the typical corre-lation betwen family socio-economicstatus and student achievement of40 to .50 is mediated in part by differ-ential experiences of children in fam-ilies at different socio-economic levels,then the correlation should be higherif a direct assessment were made ofthe child’s environment rather thanindirectly through characteristics ofthe parents. Ratings of environmentalstimulation based on parental reportswere found to correlate .69 with mea-sured intelligence and .80 with schoolachievement. These correlations, whichseem almost too high to be true, sug-gest that differential early stimulationaccounts for part of the differences inperformance of students from differ-ent socio-economiclevels.So there are clear indications that

the family factor is an importantsource of individual differences inability, but as yet we don’t know justwhat the critical experiences are, or

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much about their timing except thatthey occur very early in life—probablybefore age three or four.

THE GENETIC FACTOR

In contrast to the scant informationabout the family factor there is fairlyconvincing evidence that the geneticfactor is a major determinant of in-dividual differences in ability, Erlen-meyer-Kimling and Jarvik (1963) havecleverly plotted the results of 52studies from the literature to showthat the similarity between pairs ofpeople increases steadily as their gen-etic relationship increases from a cor-relation of .00 for unrelated personsreared apart through .50 for parent-child and sibling pairs (including fra-ternal twins) to .87 for identical twinsreared together.

In our study of twins that partici-pated in the National Merit TalentSearch (Nichols, 1965) we found anintra-class correlation of .87 for thecomposite screening test score for 687sets of identical twins and a correla-tion of .63 for 482 sets of fraternaltwins. There are so many methodologi-cal problems with twin correlationsthat it is dangerous to use these cor-relations to compute exactheritabilitycoefficients, but it is difficult to con-clude that there is not a sizable ge-netic component in ability measures.Our findings are typical of twin cor-relations found in most previous twinstudies—all using different tests andmany conducted in different lan-guages.

In addition to the twin data, anoth-er convincing line of evidence for the

importance of the genetic factor comesfrom adopted child studies where theintelligence scores of the child havebeen found to be much more related to the educational level of thetrue mother, who did not raise thechild, than to that of the foster moth-er who did raise the child (Honzik,1957).A rough ordering of the major fac-

tors in terms of their importance fordetermining individual differences inability in the United States might be—going from least to most important—the school factor, the family factor,and the genetic factor. It is interest-ing to note that this is exactly the re-verse order from a ranking in terms ofthe amountof effort and attention de-voted to these factors in our attemptsto improve the performance of ouryoung people. Indeed, it is probablythis very distribution of effort that hasresulted in the findings we have dis-cussed. The more we succeed in equal-izing the effects of a particular factorin the population, the less importantthat factor will become as a source ofindividual differences.Educators typically react negatively

to evidence indicating the importanceof the genetic factor, undoubtedly be-cause of the apparent pessimistic im-plications. To the extent that ability isgenetically determined, it would seemthat there is that much less hope forthose of us who are already born.However, when we understand more

about the genetic mechanisms, thesepessimistic implications may disap-pear. For example, studies of the ge-netics of behavior of mice, exemplifiedby the work of McClearn (1964), show

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that there is a large interaction pe-tween heredity and environment. Theeffect on behavior of a particular en-vironmental experience differs, de-pending on the genotype of the ani-mal. To the extent thatthis is also trueof humans, there are important impli-cations for education. The same edu-cational experiences may not be op-timal for everyone—which is some-thing that educators have been sayingrecently—and educational effects maybe considerably enhanced once weknow enough to administer the righteducational experience at the righttimeto theright genotype.

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