UNIT 8 FACTORS PRODUCING

INDIVIDUAL DIFFERENCES

Structure

8.1 Introduction
8.2 Objectives
8.3 Heredity and Environment
8.3.1 Nature o f Heredity
8.3.2 Genetic Basis of Individual Differences
8.3.3 Nature o f Environment
8.3.4 Environment and Individual Differences
8.4 Interaction
8.4.1 Interaction o f Heredity and Environment
8.4.2 Misconceptions Regarding Heredity and Environment
8.4.3 Implications for the Teacher
8.5 Let Us Sum Up
8.6 Unit-end Exercises
8.7 Suggested Readings
8.8 Answers to Check Your Progress

8.1 INTRODUCTION

There has been a debate for a long time on the issue ofthe relative influence of heredity and
environment on individual differences. Lately it has been accepted that the ipdividual's
, observed behaviour is actually determined by both heredity and environqent. Why do
individuals differ? What are the factors which are responsible and to what extent is the
knowledge of these variations important for us to know in order to improve the behaviour
of our students? This is an area which should be explored fully.

You would like to know about various factors which influence the development of the child
so that appropriate instructional strategies are developed and implemented to suit each learner
in a homogeneous or heterogeneous group. In fact, no educational or instructional method
or strategy can be developed in the absence of such information as underlying all such
strategies in the assumption that various factors contribute towards individual differences.
The explanations or preference for a particular subject may also be provided in terms of
different hereditary and environmental factors.

In Units 5,6, and 7, you have studied individual differences in detail. In Unit 7 we discussed
gender issues concerning male and female children. In this unit. we discuss the factors
which cause individual differences. As you know, heredity and environment related factors
have a strong bearing on individual differences. These two concepts and their educational
implications will be discussed in this unit.

8.2 OBJECTIVES

This unit is aimed at explaining the various basis of individual differences. Individual
differences are not the result of a single factor. Therefore, it is necessary for you to
understand the specific contribution of heredity and environment related factors so that
each child's behaviour is correctly analyzed. Both problem-specific and general methods of
correction should be utilized with a view to helping the student achieve the goals.
 Factors Producing
After going through t h ~ unit,
s you should be able to : Individual Differences

discuss specific contribution of hereditary and environmental factors to individual

differences,
differentiate between genetic and non-genetic factors,
explain the child's behaviour in terms of genetic and non-genetic factors, and
describe corrective measures with a view to achieve learning goals by the child.

8.3 HEREDITY AND ENVIRONMENT

To achieve the above-mentioned objectives it is very important to understand the compo-

nents affecting learning abilities. In this section we discuss the nature of heredity and
environment.
C

8.3.1 Nature of Heredity

Before discussing the contribution of hereditary factors let us see what is meant by heredity
when we talk of heredity we usually have biological heredity in mind. The term 'heredity'
may also be used in another sense, for example, if a child is brought up in a particular social
environment say of a tribe, the value of that tribe and the norms of that tribe are inculcated
in him through other members of that social group and we call it social heredity. In the same
way, a student in a classroom situation brings with him a specific cultural heredity' also.
Here in this section our discussion will be focused on the influence of only biological
heredity on individual differences. Each individual has a specific set of potentials which
are developed through the environment. These potentialities and characteristics possessed
by the individual are the result of his biologically heredity. The influence of heredity is so
strong that twins brought up in drastically different environment show very much similarity
in terms of their mental abilities and other traits. This shows that even drastically different
environments are not capable of overcoming hereditary influences.

8.3.2 Genetic Basis of Individual Differences

Basically while talking about heredity we invariable mean genes received by the individual
from his parents at the time of conception. These genes are found either in groups or exist
singly. These combinations of genes are called chromosomes. Similar chromosomes from
pairs and are very similar to each other in terms of appearance and characteristics. The
number ofthese chromosomes is the same in one type of species. Each human call contains
23 pairs of chromosomes. These chromosomes may be seen only with the help of high
powered microscopes. Each individual at the time of conception is in the ford of a single
cell which divides itself into two daughter cells which again divide themselves. This process
goes on and ultimately results in a matured organism. When these cells divide themselves,
each cell has two identical sets of chromosomes resulting in identical heredity. Whicb cell
will develop into a skin cell and which one into a bone cell depends upon the cellular
environment. Genes of the individual interact with this cellular environment in various ways
. during the process of specialized development of different cells. A different type of cell
division takes place at the age when the individual attains sexual maturity which results in
specialized reproductive cells. This process is called meiosis. Meiosis involves two cell
divisions, during which the chromosome number is halved.

Individual difference is the result of a number of possible combinations of genes. It is avery

complicated system in which even a simple looking and small characteristic is the result of
various genes. As is apparent, individual germ cells of each parent and those of two parents
i.e. mother and father have a number of possible combinations of genes. This results in
individual difference between two siblings. Since identical t\\ ins develop from the division
ofa single fertilized ovum they are identical in terms ofheredit! Rut fraternal twins are unlike
each other in terms of appearance, except that is siblings ma! resemble each style.
49 .
llndcrstanding the
Learner as a Unique
Physical characteristics are a result of heredity. Various physical characteristics i.e. colour
Individual
of hair, eye, skin, etc., are the result of various co~nbinationsof genes. If an individual
receives two genes of albinism from the parents, the person will be an albino. Such an
individual will be called homozygous with reference to albinism. If the individual gets
albinism from one parent and normal colouringfrom another, he will be called heterozygous.
Since normal colouring is dominant such individual will have normal colouring.

Even the sex of the individual is determined by the pair of chromosomes the baby receives
from the parents. When the individual receives X chromosome from both the parents, the
sex will be female. But if the individual receives X chromosome from the mother any Y
chromosome from the father, the sex will be male. Additionally, certain genes which are
received by the individual through X chromosome result in sex-related characteristics. One
good example of this is hemophilia-widely known as colour blindness. A female receiving
one dominant gene of hemophilia from one parent and one normal genes from another parent
is not likely to have this disease as the normal gene will dominate the hernophilis gene. In the
case of a male if a dominant hemophilics gene is passed on to the individual by the mother,
the individual is likely to have this disease as the Y chromosome of father will not carry this
gene at all. Hence there is no possibility of receiving any normal gene from the father. The
same is the case with blindness. A male is likely to inherit it if either of the parents pass on
this gene but a female will have it only when received from both the parents. There are also
some other factors called sex limited factors which are present in the individual.

Heredity and mental development : The fact that the mental development ofthe individual
is limited by heredity has been established lately. Watson claimed to train any healthy child
into someone expected or desired. This concept looked possible till experiments on animal
breeding proved that some kind of mental ability could be inherited. The early experiments
on rats were conducted by Tryon ( 1942) at the University of California and by Heron (1935)
at the University of Minnesota. They studied wide differences in maze learning (finding a
way to a cheese through a maze) done by various groups of rats. The ability to learn maze
was studied over generation after generations and it was found that with each generation the
groups drew further apart. Rundquist (1933) after twelve generations of selective breeding
obtained gtoups of active and inactive rats which referred to temperamental or motivational
characteristics. Many psychologists interpreted these characteristics of rats as analogous to
human intelligence. When these bright and dull rats were exposed to other learning
problems. it was found that bright rats were not good at everything. This became further
evident in the experiments conducted by Searle (1949). He found that rats from each group
showed a characteristic pattern of high or low scores which were quite different for each
group. The dull group performed as well as bright group on many learning tasks that did not
involve mazes. In general it was found that the maze bright animals were characteristically
food drivers, economical of distance, low in motivation of escape from water and timid in
response to open spaces, as against dull rats who were relatively better in water motivation
and timid of mechanical apparatus features. These differences were more temperamental or
motivational than cognitive in nature.

As has been stated earlier, the fact that identical twins cannot be made to differ to any great
extent indicates the strong influence of heredity. How are some very bright children found
among the under-privileged, rural, semi-skilled or unskilled labourers when their environ-
ments are uniformly discouraging for every member? The answer lies again in heredity.

Then there is the famous study conducted by Arthur Jensen of the University of California
at Berbely on genetic differences where it was found that white children were genetically
superior to black children. This argument claims that I. Q. has an extremely high genetic
factor (about 80%) and that there must therefore, be racial differences in intelligence. This
study was later on criticized and results questioned by many researchers. Jensen based his
argument on theconceptofheriditability. Heriditability is the proportion ofthetotal variability
in a population which is due to genetic, as opposed to environmental factors. Since I. Q. is
the result of heredity. environment and critical period (kaal), the heriditability value for 1. Q.
lies somewhere between 0 to 1.00. Jensen argues that the actual value is somewhere near 80.
You should not forget that heriditability does not apply to any single individual. According Factors Producing
to Jerry Hirseh heriditability only explains variation in some particular population at asingle Individual Ditrerences
generation under one set of conditions. Therefore, the question of high or low heriditability
is not significant for us.
-
In a study conducted under the Project called Head Start, the programme typically involved
teaching disadvantaged children on how to get along In school six months before they got
there. By the time these children were enrolled, they ka.1already gone through various critical
learningperiods. This shows the impact of improved rogramme onchildren's achievement.
Some such studies while not refuting the importance of heredity on intelligence make it clear
that the time factor and the environmental factors are extremely important in determining later
levels of intellectual functioning.

Robert Carkhuff ( I 97 I), an expert in the field of counseling and human relations, makes the
point that although the mean 1.Q. of black children is about 86 when they enter first grade,
it drops ever lower by the time the children reach fifth grade. He attributes this drop to
environmental factors working on the black child in the school setting. Sihce teachers often
treat black children as ifthey were devoid of intellectual resources, the children begin to fulfil
this expectation by achieving less and less as the school years go by. One of the reasons for
this drop relates to the placement of the eleast competent teachers in these schools. It is the
reform not surprisingthat black children often do not progress beyond the VIIlth or IX grade
level, since it may be that the level of their teacher's (non) competence does not help them
beyond that point. One study found that two -thirds of the teachers tested stood lower than
junior high school level on a proficiency test.

Heredity and family resemblances in intelligence :Though scientists will not find it very
convincing to believe, yet for a common person, resemblances among the famiIy members
in terms of intelligence is an indicator ofthe influence of heredity on different abilities of the
.same family. Some systematic studies have also been conducted to see the influence of
heredity on behavioural pattern ofthe members ofthe family. The problem withsuch studies
is that in a family it becomes difficult to differentiate between the hereditary and
environmental influences. It is true that the members of a family do not have the same
heredity but genetically they can be considered more alike than persons chosen randomly.
If, in a sample of large family groups one notices intragroup similarities, it may be attributed
to their heredity while the rest ofthe influences might have been caused by the environment.
These researchers have tried to test the following hypotheses:

If environment is an important factor in the production of intellectual traits, correlation

coefficients between siblings should be lower for these traits than fin physical
characteristics like eye colour, height and head measurement, which are thought to be
almost entirely hereditary.

If environment is an important factor, correlation between like-sexed siblings should be

higher than those between different-sexed siblings. The environment is more closely
similar to the two brothers or two sisters than it is for a boy or a girl in the family.

If environment is an important factor, correlations between siblings should be higher

than correlations between parents and children. The fact that they belong to the same
generation would operate to-make the siblings' environment more similar.

Ifenvironment is an important factor, correlations between mothers and childrenshould

be higher than those between fathers and children. The mother is more closely associated
with the children during their early formative years.

Scattered evidences have been cited both for and against each of the hypotheses presented
above.

The best evidence of hereditary influences on human psychological traits also comes from
studies of twins. As you have already studied earlier in this sub-section, the best way to
Understanding the' evaluate the influence of envirolunent is to hold heredity constant. This could bc demonstrated
L e a n e r ns n Unique
Indiviclual
by working with two monozygotic twins (who are exactly like each other in tern~sof their
genctic possibilities) but are separated and kept under two different types of environment. The
best way to cvaluate the influence of heredity is to take subjects who experienced the samc
environment but who are known to differ in genetic endowment and compare them u-ith a
group in which both heredity and environment are the same. This could be dolie by comparing
the amount of difference between identical twin pairs with the amount of difference between
fraternal twins or between siblings. Two terms viz., concordance and disordance arc uscd
in such stlldies. If both the twins show certain characteristics, they are called to be
concordant. In casc only one twin shows it and the other does not. they are called discordant.
Whenever the percentage of concordant pairs is much higher in case of idcntificd hvins than
fraternal twins: there is a sound basis for coiicluding that the traits in question have a genetic
origin. It is the consistency of the hvin resemblaiiccs from tiliie to time and from place to
place that is more impressive. Later on, some morc rcscarchers becamc intercsted in finding
out whether aptitudes and other kinds of iiitellectual abilities also have some genetic roots.

Let us prgseiit some more studics on hereditan, influence for your information and
understanding.

The role harcdity plays in certain kinds of psychiatric difficulties has been established by a
large-scale study of Ncw York Psychiatric Institute under the leadership of Kallanian (1 950).
The procedure adopted in such studies was to start with a group of persons with certain
diagnosis and then to locate and check up on their blood relatives. While much infomiation
has been accumulated about family niembers who show all degrees of relationship to the index
case. it is the figures for the twins that are most meaningf~il. In case of individ~~als with
schizopluenia (psychosomatic disease), it was found if one of a pair of identical twins has
tlie disease, the chalices arc that eighty-six tilnes out of a hundred the other twin has it also.
The other fourteen who are iiot fraillily schizophrenic are found to have schizoid personalities.
Many more such studies have also been conducted to show the influence of heredity on the
persollality of the individual.

Significant research work has also been done to stud!- neuroanatomical traits in the house
mouse and the determination of associated differenccs in behaviour. This collaborative
research wals done by a genetics interested in bchaviour and two psychologists interested in
genetics. One of the questions addressed concenis the extent to which behaviourally variablc
traits, particularly those within the so-called normal' range of variability. are due to genetic
variability among individuals. Another such question rclates to the nature ofbeliavioural traits
which have a high genetic component. Stores (1967) found highly significant and substantial
strain differences. Studies on brain weight providc an ample basis for optimislii with regard
to our f~lturoability to manipulate at least some of the compound traits ~vhichunderline it.
Heredity is high and many locii appear to be involved. On thc basis of studies of inbred strains
done by Roderick et al. (1973), and R. Wimer et al. (1969) show that identifiable genetic
control exists for the sizes of some specific portions of the central nervous system. Another
question related to selective breeding is whcthcr therc are detectable associated differences
in behaviour. A great deal has been learned from various studies conducted in this area.
Evidence was available for at least a moderate association between brain weight and reversal
leaniing in the water maze (Elias, 1969; Fuller et a l . (1973)). Studies conducted by Terris
(1964), C.Wimer and Prater (1966) and Wimer et a l . (1969) provided some evidcncc to
support a positive association between brain weight and activity in the open field.

All the studies quoted above point to the potential value of bchavioural studies. It is possiblc
to identi& some substantial behavioural differences when house mice differ with respeet to
brain weight' or with respect to the size of some specific portions of their brains. It is quite
possible that a substantial part of the genetically associated variability in behaviour which
occurs in house mice will eventually be found to be able to differentiate in brain morphology

8.3.3 Nature of Environment

So far you have seen what heredity is and how it produces indi\.ldual drfferences.No\\ you
may like to laow about anot1;er factor callcd environment and learn how it influenccs Factors I'roclucing
individual personalih in various ways resulting into individual differences. The concept of Inclividual Differences
environment needs little clarification when we say the environment of the child is not good,
sometimes 1t.emean that he is living in a localihswhich does not liavc desirable people or we
mean that he is living in the n ~ r a area
l where he does not have access to man). things which
an urban environment ma?. pro~iide.Psycliologically speaking, it is wrong to say that hvo
children colning from the same family have the same or an identical environment at homc.
The envi~.onmentfor the youngest child in a family is different from the environment
for the eldest child as the treatment to, and expectation from: both these children would be
different in each given situation. Besides, the past experience of each child will be different
which would make the present also different. As has rightly been said. the psychological
enviroturicnt consists of the s u n total of the sti~nulationthe individual receives from
conception till death. This is an active concept of environment i.e. the physical presence of
objects does not in itself constitute environnient unless the objects serve as stilnuli for tlic
individual.

The role of the prenatal enviroiunent on the development of the child is well known and has
been denionstrated through various experiments. The diet a mother takes at the time of
pregnancy, her mental status, glandular secrctions and even the thinking process influence
the developlnent .of the child. Environmentalists finnly believe that. under favourable
circi~mstaiices.every individual is allnost infinitely improvable. Let us see what role
cnvirolunent plays in deternlining individual differences.

Check Your Progress 1

Notes : a) Write your answers in the space given below.

I i)
b) Compare your answers with those given at the end of the unit.
What is heredity'?

ii) How genes are responsible for individual differences'?

I ui) Match the list:

I
A B

a) Genes are found in from the parents

b) The coinbination of in terms of heredity

genes

c) Each human cell in terms of appearance

contains
Understanding the
Learner as a Unique
d) Skin cell and bone are called chromosomes
Individual
cell depends upon

e) Identical twins the cellular environment

develop from the
division of a single
fertilized ovum.

f) Fraternal twins are 23 pairs of chromosomes

unlike each other

g) A person will be an group or exist singly.

albino when he receives
two genes of albinism.

8.3.4 Environment and Individual Differences

The studies conducted on identical twins brought up in different home environment, as has
been discussed, are the best example of environmental influences on individual differences.
Though most of us, except identical twins, get fifty percent of our genes from one parent,
we are likely to develop hereditary characteristics quite different from that parent. Thus
differences between parent and children or siblings do not prove anything about the effects
of environment. But the same can be demonstrated in case of identical twins as they are
identical to each other in terms of their genetic heritage. You may like to know' about some
researches done by separating identical twins at an early age and rearing them in different
home environment. Foster homes provide different environment to study its effect on
identical twins under controlled conditions. By doing careful analysis ofthe results one could
easily find out how much difference the environment makes in shaping personality and what
is it in the environment which is important in producing these effects. Newman, Freeman
and Holzinger (I 937) conducted thorough research on nineteen pairs ofidentical twins reared
in different environments. Initially they found that the pairs reared apart show mere
differences in I.Q. But Woodworth (1941) in his analysis of the results pointed out a factor
called error of measurement that istalways involved in intelligence testing. When this factor
was taken into account and results interpreted, Woodworth concluded that environmental
differences do operate to produce 1.Q. differences in persons with exactly the same
hereditary potentialities. But the magnitude ofthese differences is not as large as those found
among children whose heredity is not alike.

Special component ofenvironment influences intellectual development ofan individual. Case

studies have been very helpful in understanding what it is about the environment that makes
a difference in intellectual development. Woodworth demonstrated that educational influ-
ences can produce I.Q. differences in persons having the same heredity but it is the large
rather than the minor environmental discrepancies that are important. Though Newman,
Freeman and Holzinger (1 937) tried to identify the factors present in the environment which
produce personality differences in separated identical twins, their results were not that clear.
One of the reason was the non-availability of a good personality test at that time. Their case
studies included several examplesofmarked differences in superficial personalitytraits. Two
main conclusions drawn from the studies of identical twins are as follows:

Marked educational differences can produce substantial differences in measured

intelligence.

Intellectual differences in the population as a whole are too large to be accounted for in
terms of environmental differences alone.

As ateacher, you may be interested in knowing about the impact ofagood educational system
on the individual. Results of such studies would seem to justify a moderate optimism with
regard to the social usefi~lnesso f a good educational system. It means it is quite possible that
the intelligence level ofthe population as a whole can be moderately increased. What we are Factors Producing
not justified in assuming this is that individuals with low intelligence can be brought to the Individual Differences
level of the bright ones through a good system of education,

.Children in foster homes and institutions

In addition to the studies conducted on identical twins, a number of research studies have
been carried on children adopted by others and brought up in good homes. But these studies
cannot be called very scientific as the studies are not carried out in two situations i.e before
and after adoption and in this situation it becomes difficult to pinpoint the effect of
environment on the developmerlt of the child. Another important aspect of these studies is
that while selecting a foster home for a child. the concerned agencies try to locate homes
where the child with his intellectual abilities and personality could be adjusted. This factor
is called selective placement.

In one of the earlier studies, attempts were made to find out how successful adopted children
were in their life. These studies used the simple capable personalities as the criteria. 77
percent of the subjects were found to be capable, only 10 percent were delinquents or
vicious. Burks (1 928) compared a group of adopted children placed within the first year of
life with a control group ofown children matched with the adopted children for age and sex
and living in homes matched with the foster homes for locality and occupational level. She
found that a superior home can result in a moderate increase in a child's tested intelligence,
but can not bring him to the level of individuals who have both superior heredity and superior
environment. It also appeared that while there is a slight tendency for the intellectual level of
adopted children to correspond to that of the home in which they are reared. it is not nearly
so close a relationship as that which holds for children in their own homes. Leahy's (1935)
study was also much closer to Burks study in terms of its findings. All these studies agreed
in their findings and led us to believe that the average intelligence of adopted children was
somewhat higher than that of children in homes of the educational level from which they
come. They were also in essential agreement with the findings ofthe identical twin research
studies in which marked educational differences were shown to produce moderate I.Q.
differences.

Some more research findings

Findings of the above studies were challenged by researchers at the University of lowa. The
studies conducted at the University of Iowa showed that the environment exerts a much
larger influence than that which had been ordinarily attributed to it. In one of the studies it
was found that the older the children were, when they entered the orphanage, the lower their
I.Qs. were. It compares the results on the increasing retardation with age of isolated groups.
In another study of the University of lowa it was found that children placed in the superior
adoptive homes turned out higher on the average than those placed in the less superior
environments.

It is not enough to talk in generalities about environmental influences. Let us study the impact
of some of environmental inputs that appear to affect a individual's personality and
intelligence. One of the environmental factors is nutrition. Gross deficiency of diet can
adversely affect I.Q. and even produce mental retardation. Kwashiorkor, an illness resulting
from a protein-deficient diet has been found to be extremely damaging the intellectual
developement. A specific variety of pulse (Khesari) available in certain area of Madhya
Pradesh in lndiaresults incrippled individuals. Ifthisdeficiency occurs duringchiIdhood the
impact is pronounced. Though the exact relationship between protein deficiencyand mental
developments is unknown. however, recent studies have led to some speculation that
inadequate protein intake prevents full development ofthe brain especially those areas which
are involved in memorystorage. Recent introduction ofmid-day meal scheme for all children
studying in school going children may prove to be a motivating factor resulting in high
enrolment and low dropout rate. Various states in Indiahave already introduced this scheme
for tribal children with a view to attract them to the school.
Understanding the Sorlie psychologists have emphasized that tlie key to cogniti\.e growth is matching the child's
Lea~nerHS a Unique
lntliviclual
present intellectual ability with just the right amount of stilnulus varlet?.. lisants must be
exposed to a wide variety of stimulus inputs arid a sl~iftiiigenvirorunent ifnonnal intellectual
. growth is to be maintained. Bloom ( I 964) has emphasiscd that an abundant carl~renvironment
is the key to the full dcvelopiiient of intelligence. David Krecli has shown that ~vitlioutstimulus
heterogeneity animals are lcss able to learn and their brains ncyer devclop fully.

The threc crucial environmental variables listed by Blooln (1 964) are:

the amount of stimulation children receivc for vcrbal development. .

the amount of affection and reward childrcn rccei~c rrom verbal reasoning accomplisli-
ments, and
the amount of encouragement children recenlc for actnc in~cractlonwit11 problems.
explorat~onof tlic environment for leanilng of nc\\ skills
In a recent attempt Murlidharan and Srivastava ( 1995) cxamined thc impact of temple ecolog~
on cognitive development of children. In pariicular. tlic impact of gro~vingup in thc vicinity
of Hindu te~iipleson cognitive developnicnt of grade I and 1V childrcn IT as csamincd. Children
associated svitli temples emergcd to be liiorc cogniti\ cly competent than children from non-
temple areas. In another study by tlic sanic rcsearclicrs. a facilitatory effect of temple on
achievement was observed. Thesc results poilit to thc role ol'tlic templc inst~tutionin shaping
developmel~tof children by providing rich and var~egatedccologj .

Desh and K;t;tl (place and timc) are two important cllvironmcntal ~~ariables jvhich exert
.influenceon the total personality of tlie indi~ridual.Thc placc and its environment. as we have
seen iidue~zcesattihtdes?interests and o\-erall dcvelopmcnt of the individual. Same individual
placcd in different environments at various times is likely to ediibit different beliavioural
pattenl. 111the salue way a child slio~vsdifferent behaviour in different subject pcriods or at
different placcs viz. play ground, home, and school.

Kaal or time is an equally imnportant environmental variablc as age,increascs intellectual

developincnt increases -less. Initially the specd 1s fastcr wh~clibecomes slowcr and slower
with age. Bloom fccIs that the difference bct\vcen a beneficial and a stufT~ngeniirolunent
during these carly childhood years can producc I.Q. diffcrences of 20 points. The study
conducted by Wayne Dennis of a Teheran Orphanage where children wcrc kcpt in, a condition
of extreme sensory deprivation also showed that stimulus variety at an carly age is critical for
cogniti~;eg,rdt\ith.Almost all of tliosc senson-deprived children wcre intcllcctually retarded.

' Since no indikidual is beyond Desli and Kal, it is important to view tlie individual's personality
in thc contex(ofp1ace and time and not in isolation. The illfluence ~Ethese'variablesis so strong
that hereditary influences are overshadowed by them. Thus the teacher has access to various
nietliodologies for shaping and reshaping the learner's bcha\.iour.

Check Your Progress 2

Notes : a j Write your answer-in thc spacc given below.
1I
b) Compare your answer with those given at the cnd of tlic iuliit. 1
How do heredity and environnlei~tcontribute to individual differences? I
Writc your answcr in four lines.
 F ~ C ~ H I'racluring
I.S
8.4 INTERACTION l s d l \ ~ i d u a lDltYcrrnrcs

In tlic prcceding section you have studied thc impact of both lieredity and environment on
liunlan bchaviour. You might have observed tliat neithcr lieredity nor environment is tlie sole
deteniient or individual bcliav~our.The causes of behaviour are niultiple and complex.
Hereditarians and cnk iro~ui~entalists
argued in their favour and created a division in tlie field
. of psycholog!: Tlic solut~onto the age old controversy is tliat behaviour is the result or
hcredit? interacting with en\.iro~uiientand both interacting with time (kaal). This statenicnt
will help you to answcr Clicck Your Progress 2.

8.4.1 Interaction o f Heredity and Environment

You ha\-c scen tlic influcncc of lieredity or cnvironmcnt on thc growth and dcvclopnicnt of
tlie individual. as established by various rescarch studies. Today most of us believe firnil?
tliat hunian beha\,iour and personalit? are the result of both heredity and environnicnt. It is
now rccogni~cdthat c l c n trait and rcaction of tlie individual that hc manifests dcpcnd on
both liis liercdity and enviroruiient. Still an attclnpt to classi+ behaviour into hvo catcgorics:
innate and ;required. is madc. But onc should kno\c that hereditary and envirorunental
factors ca~uiotbc sortcd out in sucli a fashion. nor can bcliaviour bc divided into tliat which
is inherited and that which is acquired.

kiollier approach to lieredity and en\~ironmentis hiown as additive contribution wliich

niearis tliat both of tliese detenninc human beings growth and dcvclopnient and tlic resulting
behaviour is the sun1 of Iiercditaq and environniental influences. But it n.ould not be wisc
to attribute a fixed propottion of tlie development of one bel!aviour to hercdity and anotlier
to tlic cn\riro~uiient.Therefore tlie most logical explanation would lie in interaction ofheredity
and cn~,ironmentwliich would mcan that the effects of hcredity aiid environnent are not
cunli~lativeor additive. The nature and extent of tlieir influence depends upon the contribution
of each other. To sap it more explicitly. an environmental factor cxerts different i~lfluenccs
depending up011 the specific hereditary background. Similarly. any hereditary factor will
operate differently undcr different environme~italconditions. Under this assuniption,
lieredity and environmelit do not have fixed proporti011of contribution. rather the cstenl of
their colitribution varies as hereditaq and.cnvironnienta1factors vary. Tlicrcfore tlierc could
be as many combinations as the number of situations.

The relationship between the two types of factors would vary from a v c e simple one to the
most co~ilplicatedbeliaviour. For example in the case of determining body weight it may riot
bc possible to predict a one-to- one relationship as the weight would largely depend on the
diet one takes, the'intake capacity of the person and hereditary factors, In the case of
behavioural traits. it is still more futile to look for a single figure to express thc contribution
of these factors. Both these factors are interdependent and interdependence mcans that tlie
influence of any given environnicntal factor on a particular trait depends upon the individual's
specific liereditan background and in thc same wvay the influc~iceof any given hereditar)
[actor depends upon tlie specific enviro~mlentalconditions within which it operates.

Another aspect of this interaction refers to the occurrence of changes as a result of slight
*riati011 in oneof the hvo factors. It is also possible that a slight variation in theenviro~lniental
factors and a slight difference in the hereditary factors would lead to wide vanation in the
resulting trait or beliaviour which may furtlier influence the total process of development.

57
i~~~cleratilncling
the
Lernwr us u U~lio
lndividurl Check Your Progl-ess 3

Notes : a) Write your answer in the spacc given below.

b) Compare your answer with those givcn at the end of the unit
Are hereditary and cnvironmental factors dependent upon each other for the develop-
ment of the behaviour of a child'? Esplain bricfl?

8.4.2 Misconceptions Regarding Heredity a n d Environment

While dealing \11itIi heredity and environment in the contest of individual differences. one has
to bc cautioncd against niisuse of terriis like inborn. acquired. resemblance, maternal
impressions. etc. For esample. take tlie tenn 'inborn.' The hvo tenlis i.e. inboni and lieredit?..
are somelinics used interchangeably. It is usually belicved that whatever is inboni is hereditan.
Another related ~iiisbcliefis that taking birth is thc end of heredit?,. Both thcsc \ie\\:s are
misconceptions. Hereditary-s influences may be visible at the later stagc. bl thc same way.
environmental factors sta,rt exerting their iduencc much bcforc tlic birth i.e. during prenatal
period. Therefore. thc influences of heredity and environment co-exist in time. Birth is not to
be regarded as the end or beginning ofone hpe of influence as it is only a stage,ofdevelopment.
. .

Another such inisco~~ccption relates to parental rescmblance. Heredity does not neccssaril)
resi~ltIn resemblance of offspnngs to the~rparents. S~ncegenes glven b?. parents to the~rOK-
springs are not produccd by parents but are passcd on to tlieni by their ancestors. it is not
neessary for the off-spring to resemble one of the parents. hi the same \\a> what we call
parental resemblance may be the influence of some env~ro~unental factor result~iigin such
similarity.

Another such misconception is about transn~ittingacquired or trained skill to the off-spring

by tlii parents. Heredity does not refer to any sucli transmission as these skills or beha~iour
are consciously learned by the parcnts and do not fall within the pun~icw of heredit\.. The
experiences of the mother during pregnancy and their inipact on the individual should also
not be confused with heredity. Only some indirect biochemical effects may be coiis~dered
for this purpose.

Another common misbeIief relates to the modifiability of characteristics attributable to

heredity or environment. It is believed that if a hereditap origin is identified under a given
cond~tron.nothing or very little can be done to improve it. This is not true. Man? heredita~
diseases are curable. Traits having hereditary basis respond to environmental factors likc diet.
exercise. training. etc. In fact there are very few hereditary characteristics that cannot be
chaiigcd by an? hio\vn cnvironmental factors. In the same way tliere is a false belief that
acharacteristics of. or differences between individuals attributable to environment can be
changed easily. In fact such environmentally produced changes or behaviour are as real as
hereditary and cannot be done away with so easily.
 I 1;nctnrs Produrlng
I 8.4.3 Implications for the Teacher Incllvldunl Differences
I
1
As a teacher you would like to know about the implications of hereditary and environmental
I backgrounds for the teaching-learning process. As you have seen, there is evidence available
to prove that the measured intelligence of individuals or groups of individuals is related to
some extent to their educational experiences. There are intellectual differences in terms ol'
the aniouiit of foniial education, even in cases of sibliiigs who initially look alike. Besides,
studies have shown that many individuals originally labeled as feeble minded or mentally
retarded become able to function as nonnal persons 111their communities after receiving the
right kind of education or training. This is indicative of the positive impact of a stimulating
environment on the development of the individual. Therefore, it is necessary to provide a
favourable stimulating and supportive educational atmosphere to children coming to the
school.

I11 fact. whether it is curriculum development, teaching strategies or guidance. knowledge

of one's heredity and environment backgrounds, and their impact on an individual's
personality is very handy to teachers and curricululn developers. Educationists conccmed
witli pedagogical issues always attach immense importance to the selection of proper
teaching methods to suit the need of the students.

The selection and placement of children in various groups should be done on the basis of their
qualities, skills and talents. Illformation about these aspects can be collected by the teacher
through observation alld testing cognitive styles and personality traits. Students need
educational guidance to either select a suitable course of study or to improve tllc level of their
ach~evements.Guidance also involves counselling for adjustment to educational, emotional
or social situations. Maladjustment in one area is likely to influence ad-justment in other areas
also. As has been discussed earlier. the purpose of individualized instruction is to reduce the
educational variability ainong individuals by catering to their specific needs arising out of
individual differences.

You have seen that children at a particular age might differ from each other in a number of
I ways i.e. intelligence, personality characteristics. interests, readiness to study a particular
1 area (subject of knowledge) and some physical characteristics. Individualized instruction
aims at helping every child according to his capabilities. You should understand clearly that
I individualized instruction is not meant to impart instruction to each child separately. A group
of students similar to each other in tenns of intelligence, interest. +rsonality, etc.. can be
taught together. Individually prescribed instruction (IPI): computer-assisted instniction
(CAI) and open classrooms are some forms of individualized instruction.

As has been discussed earlier, you can utilize information about every child's personality and
cognitive development for the purpose of selection and placement in a suitable vocation.
Children witli specific skills: whether obtained through heredity or acquired tlxough
1 enviromneiit. may be put in suitable groups or advised to go to a particular stream of
education. You are also aware that sometimes the school arranges special remedial classes
for certain students to help them improve their resultslachievement in the exanimation.
I
Remedial measures are effective only when you know the exact cause for poor performance
or learnmg. Even for selkcting students for competitive examinations information about
student's heredity and environment is very helpful.

Counselling should be an integral part of educational guidance in our system. The purpose
of guidance is to make the individual aware of his own interests and abilities and to guide him
in the proper direction.

What should you do? You should observe each student for the initial period carefully and find
out details about him. What are his characteristics'?, what are his interests'?, what is his
general level of iiitelligence'? On the basis of your observation you can develop specific
corrective measures to take care of his deficiencies so that he could be brought at par with
other students This will also ascertain the quality of education for each student. The moment
you become'conscious of each student's specific potential, you become a real friend of your
students
Understanding the
Leaner as r IJnique
Indiviclual
Check Your Progress 4

Notes : a) Wr~teyour answer in the space given below.

b) Compare your answer with those given at the end of the unit.
As a teacher. wbat corrective measures will you plan for a mentallv retarded and
maladjusted students
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8.5 LET US SUM UP

In this unit you have studied about the two important factors - heredity and environment
- which influence the development of individuals, resulting in individual differences. You
have also read about various research studies conducted in this field of study. Now-a-days.
it is alniost certain, and all of us also believe, that individual differences are the result of the
interaction of heredity and environment. While we recognize the importance of heredity in
individual differences, we are almost equally confident of the cole environment plays In
building up the personality of the individual. A teacher can provide a favourable educat~onal
environme~tin the school to help the child develop his potentialities. A non-favourable
environment is bound to be detrimental in the process of development of the student.

8.6 UNIT-END EXERCISES

- 1. .What are the main factors responsible for producing i~idividualdifferences?

2. ' What is the genetic basis of heredity'? Cite some studies'insupport of hereditary i~ifluences
on individuals.

3. What do you mean by environment'? How is the behaviour of the individual influenced bv .
it1?

4. What do you understand by thk interactidnal.mode1 in reference to influenkes of heredity

and environnient on personality development'? Describe it.

8.7 SUGGESTED READINGS

Dreikitrns, Rudolf (1957) : Psychology in the lassr room. Second Edition, Harper and Row
Publishers, New York.

Entwistle, Noel ( 1985).:New Directions in Educational Psychologv :Learning and Teaching,

' n e Flamer Press, London and Philadelphia.

Tvler, Leona E. (1965) : The Psychology ofHuman Differences, Third Edition. Vakils, Feffer
and Simons F'rivate Ltd., Bombay. -
60
 Fuctora Procluclng
Intllvldual Mftkrcncen
8.8 ANSWERS TO CHECK YOUR PROGRESS

1. i) Each individual has a specific set of limits \~hicllare tlie result of his biological
heredity i~iheretedfrom his parents or forefathers.

u) Each parent and those of two parents i.e. mother and father have a nuniber of
possible combinations of genes So thesc conibinatiolis of gc~icsarc rcsponsible for
individual differences.

iii) a) Genes are found in groups or exist singl)..

b) The conibination of genes arc callcd chromosomes.
C ) Skin cell and bone cell dcpcnd upon thc ccllular cnvironmcnt
e) Identical t ~ ~ develop
n s from tlie divisioli of a siliglc fertilized onun in terms
of heredit>..
t] Fraternal twills are unllke cacli otlier in tcrlns of appearance.
g) A pcrson \\.ill be albino whcn lic rcccives two gcnes of albinisiii from tlie
parents.

2. Individual differenccs is the result of a nunibcr of possible combinations of genes.

Indijidual germ cclls of parcnt and those of tlvo parents i.e.. mothcr and fathcr liave a
nuniber of possible combinalions ofgcnes. This results in individual differenccs betwecn
two siblings. Tlie environment also infl ucnces individual's personality in various wa5.s
resulting into individual differences. Special coniponelits of environment influcncc
i~itellectualdevclopment of an ~ndividual.

3 . Any give11en\-ironmental factor on a particular trait dcpcnds up011 thc individual's

specific hereditan background. In tlic same waJTthe iiifluence of ally given hcreditan,
factor depends up011 the spccific environmental conditions within whicli it opcratcs.
Thesc hvo factors would lead to widc variation and affect.tlie dcvelop~nentbehaviour
of the child.

4. Classrooln observation. dctcr~iiinctlic potential of each specific case. develop teaclii~ig

techniques along with technical nlpport.