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Quantitative Review of the Only Child Literature. Research Evidence and Theory Development


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Conducted 6 meta-analyses of 115 studies on only children (OCs) to evaluate the status of OCs. The meta-analyses focused on achievement, adjustment, character, intelligence, parent–child relationships, and sociability. Findings indicate that OCs were found to surpass all others except firstborns and people from 2-child families on achievement and intelligence. They also surpassed all non-OCs, especially people from families with 3 or more children, in character and they surpassed all non-OCs, especially those from large families, in the positivity of the parent–child relationship. Across all developmental outcomes, OCs were indistinguishable from firstborns and people from small families. Theories relating to OC deprivation and OC uniqueness were discredited by the results of the meta-analyses. The meta-analyses supported parent–child relationships as an important factor in producing the developmental outcomes attained by OCs, firstborns, and people from 2-child families. Studies included in the meta-analyses are appended. (63 ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)
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Psychological Bulletin Copyright 1986 by the American Psychological Assooiation, Inc.
1986, Vol. 100, No. 2, 176-189 0033-2909/86/$00.75
Quantitative Review of the Only Child Literature:
Research Evidence and Theory Development
Toni Falbo
University of Texas at Austin Denise E Polit
Humanalysis, Inc.
Jefferson City, Missouri
Six meta-analyses of the research literature on the only child were conducted in order to evaluate
the status of the only child and to guide theory development in this area. The 115 studies included
here generated enough information to justify recta-analyses on the following topics: achievement,
adjustment, character, intelligence, parent-child relationships, and sociability. Only borns were
found to surpass all others except firstborns and people from two-child families on achievement and
intelligence. They also surpassed all non-only borns, especially people from families with three or
more children, in character and they surpassed all non-only borns, especially those from large fami-
lies, in the positivity of the parent-child relationship. Across all developmental outcomes, only chil-
dren were found to be indistinguishable from firstborns and people from small families. Theories
relating to only child deprivation and only child uniqueness were discredited by the results of the six
meta-analyses. The meta-analysis supported parent-child relationships as an important factor in
producing the developmental outcomes attained by only children, firstborns, and people from two-
child families.
In this article we report the results of six meta-analyses of the
research literature on the only child, and use these results to
evaluate the status of the only child and to guide theory develop-
ment in this area. Since 1925, over 200 studies have been pub-
lished that either focused directly on the only child or included
only children within a larger framework of investigation. Re-
viewers of the sibling relationships, birth order, or family size
literature have bemoaned the lack of theory in this general area
as well as in the specific area of only children (B. N. Adams,
1972; Kammeyer, 1967; Polit, 1982; Rodgers & Thompson,
1984; Schvaneveldt & Ihinger, 1979). Ex post facto explanations
for observed differences between only borns and others are com-
monplace, as are inconsistencies in the research results (B. N.
Adams, 1972; Falbo, 1984; Kammeyer, 1967; Polit, 1982).
However, regardless of their theoretical orientation, researchers
have often assumed that the absence of siblings has a profound
impact on the developmental outcomes of children.
From a theoretical standpoint, only children represent a use-
ful and challenging concept. Because they do not grow up with
siblings, only borns are a natural comparison group for those
studying the impact siblings have on development. For this rea-
son, data on only borns are frequently found in the literature
on sibling processes and relationships. Only children represent
a challenge to birth order theorists, who have classified only
borns in a variety of ways. Alternately, they have been catego-
rized as firstborns, as last borns, or as a totally distinct class
We thank Jeffrey Berman for his advice on meta-analysis methodol-
Correspondence concerning this article should be addressed to Toni
Falbo, Department of Educational Psychology, the University of Texas,
Austin, Texas 78712.
(B. N. Adams, 1972; Adler, 1964; Falbo, 1981; Schvaneveldt &
Ihinger, 1979).
Finally, only borns also represent the offspring from a single
family size, the one-child family. Therefore, data about only
borns can be found in the more sociologically oriented family
size literature. Here, only borns and their families are fre-
quently considered as similar to other small families, such as
two-child families.
Prejudice Against Only Borns
Appreciation of the theoretical significance of only children
may have been hindered by the long-standing prejudice against
them. Psychologists and psychiatrists have historically por-
trayed only children as developing abnormally and acquiring
undesirable personalities and social behaviors. Hall reportedly
said, "Being an only child is a disease in itself" (Fenton, 1928,
p. 547). Later, Brill (1922) wrote, "It would be best for the indi-
vidual and the race that there should be no only children"
(p. 28).
As the science of psychology developed, investigators made
empirical comparisons between only children and others. Al-
though these early investigators were severely limited by the
tools available to them, they compared only children to others
on a variety of attributes, including IQ and teacher evaluations
of personality. In general, these studies failed to support the ear-
lier negative image of only children. One of the earliest studies
(Fenton, 1928) reported that the teacher evaluations of only
children were comparable to those given to non-only children.
These evaluations included ratings on such traits as generosity,
sociability, and obedience. In other studies, only children were
found to be more intelligent (Lentz, 1927) and gregarious
(Goodenough & Leahy, 1927), and to have fewer behavior prob-
lems in school (Blatz & Bott, 1927) than non-only children. The
major faults of only children were that teachers regarded them
as more aggressive and conceited than non-only children (Fen-
ton, 1928; Goodenough & Leahy, 1927).
Despite these early results, the popular view of the only child
was so negative that Solomon, Clare, and Westoff (1956) re-
ported that among Indiana couples interviewed as part of the
Indianapolis Fertility Study in 1941, the second most common
reason for having a second child was to prevent their first from
being an only child. By contrast, concern about being "left
childless in the case of death" was ranked fifth. This negative
view persisted through 1950 and again in 1972 when two Gal-
hip polls of U.S. national samples indicated that approximately
78% of white Americans thought that only children were disad-
vantaged (Blake, 1974). This perspective was later elaborated
by undergraduates who described only children as "generally
maladjusted, self-centered and self-willed, attention-seeking
and dependent on others, temperamental and anxious, gener-
ally unhappy and unlikeable, and yet somewhat more autono-
mous than a child with two siblings" (Thompson, 1974, pp.
Thus, throughout most of this century both professional and
lay opinion has tended to view only children as handicapped by
the absence of siblings. The results of early studies disconfirm-
ing the only child stereotype were largely ignored. During the
postwar Baby Boom years, prejudice against only borns was
manifested both by professionals, who ceased studying them,
and by the general public, who avoided having them (Taffel,
1977). However, the country's mood shifted in the 1970s when,
as a result of many social changes, women increasingly began
childbearing later and had fewer or no children (Taffel, 1977).
At the same time, the research community once again began to
study only children, focusing on such outcomes as personality
and cognitive development, mental health, and social adjust-
ment. Consequently, the research literature on only children is
now abundant, but has never been systematically analyzed
through a meta-analysis.
Status of Theory
Few of the studies on only children have been motivated by
a formal theory; instead, the bulk of this literature has been
motivated by either curiosity or convenience. The curiosity
studies were designed to determine whether a particular group
of only borns were worse off on a specified variable than those
who had siblings (e.g., Burke, 1956; Fenton, 1928). In other
words, these investigators tested the popular stereotype of the
only child. The convenience studies included an only child
group because they happened to have some in their sample and
birth order/family size information is relatively easy to collect
and analyze (of. Schooler, 1972).
Among those studies motivated by formal theories, two types
of theories can be distinguished. The most frequent is an appli-
cation of a theory developed originally for other purposes. Ex-
amples include the application of social comparison theory to
understanding the relation between self-esteem and birth order
(e.g., Zimbardo & Formica, 1963). The second type is one that
was developed solely to explain family phenomena. The most
well-known and recent theory fitting this description is the con-
fluence model (Zajonc & Markus, 1975). This model was origi-
nally devised to explain a negative correlation between family
size and intelligence.
Researchers have frequently tried to explain any observed
only child difference in a post hoc fashion. These efforts have
resulted in diverse and often conflicting propositions about the
nature of only child development. This diversity reflects the
breadth of outcomes examined as well as discrepancies among
studies in the direction and degree of differences between only
borns and others. We discuss the major explanatory mecha-
nisms proposed in the psychological literature next.
Explanatory mechanisms.
Although there are many psycho-
logical and interpersonal explanations for only child results in
the literature, the most common of these can be synthesized
into three basic explanatory mechanisms. Each mechanism has
been used to explain results across a broad range of develop-
mental outcomes.
1. Deprivation. Pervading many studies is the notion that if
siblings provide critical learning experiences for each other,
then the absence of siblings means that these lessons are not
learned. Consistent with the popular view of only children, this
mechanism portrays the only child as disadvantaged. Com-
monly, such explanations are used to motivate predictions re-
garding their maladjustment (e.g., Belmont, Wittes, & Stein,
1976; Fenton, 1928). More recently, family systems theorists
used the deprivation mechanism to justify predictions that only
borns may be more at risk than others in terms of a lack of
communication skills, autonomy, and identity formation (Mi-
nuchin, 1974). In addition, the deprivation mechanism has
been used to explain IQ discontinuities of only children in
terms of their lack of siblings to tutor (e.g., Zajonc & Markus,
2. Only child uniqueness. This mechanism (B. N. Adams,
1972; Adler, 1964) emphasizes the uniqueness of the only child
experience. Although only children share some experiences
with first- and last borns, they also differ in critical ways from
both. Only borns are like last borns in that neither is dethroned
by the birth of subsequent children. At the same time, only chil-
dren are like firstborns in that both receive their parents' undi-
vided attention during their early lives. Finally, because only
borns represent an entire family size, unlike other birth orders,
they occupy a unique theoretical category.
This mechanism is usually used to explain results indicating
that only borns are discontinuous from all others, including
firstborns and people from small families. The uniqueness
mechanism is cited to explain both positive and negative find-
ings about only borns, including greater leadership (Smith &
Goodchilds, 1963) and self-centeredness (B. N. Adams, 1972;
Falbo, 1981) than non-only borns.
3. Parent-child relationship. This mechanism emphasizes
the nature of the parent-child relationship, particularly the in-
teractions between parents and children, in determining devel-
opmental outcomes. This mechanism operates similarly for
both only and firstborns. They both share the experience of be-
ing their parents' first child and at least for a limited time, both
are the only child.
The parent-child relationship for only and firstborns has
been characterized as influenced by the high anxiety levels of
their parents (e.g., Schachter, 1959). That is, because first-time
parents know relatively little about childrearing (Waddell &
Ball, 1980), they are more anxious, which makes them more
responsive to and unrealistic about their children's behavior.
Such anxious behavior has been portrayed as causing in only
and firstborns greater affiliativeness (Schachter, 1959), achieve-
ment motivation, and internality (Falbo, 1984).
Likewise, only and firstborns generally receive more parental
attention than do later borns (Falbo & Cooper, 1980; Gewirtz
& Gewirtz, 1965; Hilton, 1967). It is easy to imagine that exces-
sive parental attention could cause undesirable outcomes in
children, such as dependency and selfishness. Recent research-
ers have taken a different tack, emphasizing the positive conse-
quences of parental attention for intellectual development and
achievement (Blake, 1981; Falbo & Cooper, 1980).
Intervening factors.
In general, these explanatory mecha-
nisms alone or in combination have been hypothesized as the
causes of differential developmental outcomes between only
children and others. In invoking these explanations it has often
been assumed that beyond the specific mechanisms, all things
are equal across families. However, this assumption may be un-
warranted. The literature on family size and birth order points
to the need to consider factors that intervene in the causal chain
between the causal agents and the developmental outcome.
These intervening factors can significantly alter the direction of
the influence of these more general effects. Of particular rele-
vance to the only child literature are temporal factors that in-
volve changes over time within history (i.e., across birth co-
horts) and within the individual.
1. History. Historical events have influenced the reasons for
having an only child and the proportion of the population grow-
ing up without siblings (Falbo, 1982). It has been argued that
early in this century, only children were more likely to be born
and develop during times of economic hardship and war (Blake,
1981; Easterlin, 1978; Westoff, 1978). The more recent increase
in the incidence of only children has been attributed to a rela-
tively high divorce rate, increased numbers of women in the
labor force, and economic recessions (Westoff, 1978).
Because of the potential covariation between family size and
historical events, comparisons of only borns to others should
consider whether one or more of the three explanatory mecha-
nisms is the cause of any observed difference or whether histori-
cal factors, such as being more likely to have come from a di-
vorced family, bring about a difference between only children
and others in developmental outcomes.
2. The individual. Changes over time within the individual
are especially significant for children. Maturation has been seen
by theorists as an important filter mediating children's reac-
tions to their interpersonal experiences. Psychoanalytic theo-
rists have argued that children's experiences in early life are
formative for their later personality and emotional adjustment
(Adler, 1964). Such theorists are likely to emphasize the similar-
ity between only children and firstborns because their early ex-
periences are similar. In contrast, others have argued that ad-
olescence and the period of launching the child into adulthood
are extremely important (B. N. Adams, 1972; Schvaneveldt &
Ihinger, 1979). Such theories are likely to emphasize the simi-
larity between only and last borns because of their shared status
of being the last child to leave home.
Because interactions between the explanatory mechanisms
and maturational changes are plausible, investigators compar-
ing only borns to others should consider whether differences are
age-related or fixed across all maturational levels.
In this article we quantitatively review the re-
search literature on only children. Because of the diverse topics
considered in studies done on only children, we compare only
children to others on a broad range of developmental outcomes.
Our goal is to use the results of the meta-analyses as a basis
for evaluating the status of the only child and advancing theory
development about only borns. This area has been marked by
the lack of such a theory, with investigators frequently relying
on ex post facto explanations for observed differences between
only children and others.
Selection of Studies
We reviewed over 200 published studies in preparation for this article.
These included all the studies we could find in the birth order and fam-
ily size literature that included only children in the sample. Studies were
excluded from the meta-analysis because (a) the dependent variable was
studied too infrequently and was conceptually distinct from the topic
areas we shall describe; (b) the quality oftbe study was too poor to merit
inclusion; (c) an effect size could not be computed, for reasons that we
shall discuss; and (d) the study's sample was identical to that used in
another, included study; and (e) fewer than five only bores were included
in the sample. We describe the results of meta-analyses based on the
remaining 115 studies that met all the inclusion criteria. (See the Ap-
pendix for a list of these studies.)
Quality assessment.
In order to avoid combining the results of low-
and high-quality studies, we evaluated all studies on a 6-point scale.
Points were assigned to the study if it possessed the following attributes
judged as desirable for a methodologically rigorous study: (a) large sam-
ple size (n > 500), (b) use of probability sampling, (c) controls for extra-
neous variables, (d) sophisticated analytic approach, and (e) use of es-
tablished instruments (e.g., a standardized IQ test).
The quality ratings ranged from 0 to 5, with 0 assigned to studies with
none of the above
attributes and 5 assigned to studies with
all of the
characteristics. Studies with a quality rating of 0 were omitted
from the analyses (n = 6).
No effect size computable.
In addition to the studies omitted because
of low quality ratings, 64 other studies were omitted because effect sizes
could not be computed. This usually occurred because (a) the results
were presented only in aggregated correlational form (e.g., the correla-
tion between family size and intelligence) without any information be-
ing presented separately for only children and comparison groups
(34%), (b) data for only horns were combined with data from either
other firstborns or others from small families (42%), and (c) insufficient
statistical information was available for computing an effect size (l 7%).
Characteristics of the 64 excluded and 115 included studies were
compared to determine whether the included studies represented a bi-
ased subset of the located studies. There were no statistically reliable
differences between included and excluded studies with respect to any
subject characteristics, such as age, ethnic mix, social class distribution,
gender mix, or country of origin. Furthermore, the two groups of studies
were similar in terms of quality rating, type of measurement used, and
the study's independent variable (birth order or family size). However,
the excluded studies were significantly more recent, with an average
difference of 7 years (1973 for excluded studies vs. 1966 for included
ones). This difference primarily reflects the evolution of analytic tech-
niques: Older studies tended to rely on analysis of variance, t tests, and
chi-square tests, whereas more recent studies often used regression pro-
cedures in which a continuous variable such as family size was an inde-
Characteristics of Studies Included in the Meta-Analyses
Characteristic or M
Source of studies (%)
Psychology 46.1
Education 12.2
Sociology 15.7
Interdisciplinary 17.4
Health/medical 4.3
Other 4.3
Nationality of samples (%)
United States 79.1
Non-U.S., English speaking 12.2
Non-U.S., non-English speaking 7.8
Gender of samples (%)
Mixed 76.5
All males 7.8
All females 11.3
Unspecified 4.4
Ethnicity/race (%)
Mixed 26.1
All white 33.9
All nonwhite 2.6
Unspecified 37.4
Social class (%)
Mixed 48.7
All middle class 20.9
All lower/working class 0.9
Unspecified 29.6
Year of publication (M) 1,966.7
Sample size (M) 15,827.7
Median sample size 1,162.0
No. of only borns in sample (M) 1,871.2
Median no. of only borns in sample 134.5
Subject's age (M) 16.6
Quality rating (M) 2.3
One-hundred fifteen studies were included in the meta-analyses.
pendent variable. In such cases, it was frequently not possible to com-
pute an effect size because the results were presented in aggregated, cor-
relational form.
Studies Included
Table I summarizes the characteristics of the 115 studies included in
the meta-analysis. Studies published in psychological journals ac-
counted for nearly one-half of the sample. Other studies came primarily
from interdisciplinary, sociological, and educational sources. The ma-
jority of studies were based on U.S. samples.
In almost all cases, the gender composition of the sample was de-
scribed in the report. The majority of studies involved both male and
female subjects. However, a disturbingly high proportion of studies
failed to report the ethnicity of their subjects. Among studies in which
the ethnic composition was described, a sizeable proportion had an all-
white sample. Relatively few studies explicitly stated that their samples
were of mixed ethnicity. Information on the samples' socioeconomic
background was also not consistently available, with one-third of the
studies providing no information. Among those studies that provided
sufficient information to code subjects' socioeconomic status, the ma-
jority were from mixed social classes. Studies that involved subjects
from working or lower classes exclusively were rare.
The 115 included studies were published between 1925 and 1984.
One-third of the studies were published after 1975. The studies ranged
in total sample size from 50 to 686,606. The number of only borns
present in each study ranged from 10 to 78,053. The mean sample size,
as Table I shows, is skewed by the handful of studies (n = 15) containing
over 10,000 subjects. Most studies (75%) had fewer than 5,000 subjects.
The subjects in the studies ranged in age from preschoolers to adults.
The samples were categorized into the following age groups: preschool
(3%), grammar school only (16%), grammar and high school combined
(22%), junior and senior high school only (24%), college age (10%), and
adult (24%). The remaining samples were of unknown age (1%).
The fact that many studies failed to report results separately by eth-
nicity, social class, and gender groups, or failed even to identify sample
characteristics made it impossible to incorporate such characteristics
into the recta-analysis. However, age of subjects and year of publication
were generally available, thus allowing these temporal factors to be in-
The quality ratings were correlated with other aspects of the studies'
methods and characteristics. For example, we learned that the quality
of studies significantly improved over time (r = .28, p < .001), a result
that primarily reflects increasing sophistication in methods of data anal-
ysis and the growing use of large, nationally representative samples in
the past few decades. The study's disciplinary orientation was also cor-
related with the quality ratings: those from nonpsychological sources
were rated significantly higher than those from psychological ones (r =
.26, p < .05), largely because the psychological studies tended to have
smaller samples.
Studies were characterized by the type of measurements used: self-
versus other report. Self-reports included data from paper and pencil
psychological tests as well as responses to survey interviews. The other
reports category consisted primarily of ratings made by observers, such
as teachers. The majority of measures (58%) were of the self-report type.
Comparison Groups
The meta-analysis involved contrasts between only children and vari-
ous comparison groups. First, only children were compared with all
non-only children (i.e., anyone who had a sibling). Additional compari-
son groups were defined in terms of birth order and family size. Three
family-size comparison groups were established: small (two-child), me-
dium (three- or four-child), and large (five- or more child) families. In
terms of birth order, only borns were compared with firstborns and later
borns from multichild families. Two-thirds of the studies permitted
birth order contrasts and 58% permitted family size contrasts. A size-
able minority of studies (24%) provided sufficient information to make
both birth order and family size comparisons.
Family size and birth order both were used as independent variables
in studying a broad variety of developmental outcomes. These outcomes
were initially classified into 14 categories. Because of the uneven num-
ber of studies represented by these 14 categories and because some cate-
gories contained too few studies to analyze, the outcomes were grouped
into the following five general developmental outcomes: intelligence,
achievement, character, sociability, and adjustment. Table 2 shows the
14 original categories and how they were grouped, together with the
number of studies in each category. As the table shows, the number of
studies within the 14 categories ranged from a low of 4 (for androgyny)
to a high of 41 for intelligence/ability. After combining categories into
the five topic groupings, there was an adequate sample for five separate
meta-analyses. Note that several studies with dependent variables in cat-
egories not shown in Table 2 (e.g., dogmatism, creativity) were not in-
cluded in the analyses because of their small number and their concep-
tual incompatibility with other studies within the five developmental
Table 2
Description of Developmental Outcomes
No. of
Outcomes studies Categories
Achievement 7 Occupational prestige
16 Motivation/aspirations
13 Educational attainment
17 Academic progress/grades
Adjustment 30 Personal adjustment/anxiety
9 Self-esteem
13 Behavior problems
4 Androgyny
Character 10 Leadership
19 Personal control/autonomy
13 Maturity/cooperativeness/citizenship
Intelligence 41 IQ/standardized ability tests
Sociability 10 Peer acceptance
24 Affiliation need/extraversion
The number of studies counted exceeds 115 because some studies
covered more than one topic. Separate meta-analyses were conducted
for each developmental outcome.
Estimates of Effect Size
For each of the comparisons, a standardized estimate of effect size
was computed according to the formula developed by Cohen (1977).
Cohen's d (the effect size) is defined as
ml =m2
where rn~ is the mean for only children, rn2 is the mean for the non-
only child comparison group, and s is the pooled within-group standard
deviation. The effect size d represents the mean difference between
groups relative to within-group variation. Although the standard devia-
tion of the comparison group only has been advocated by Glass and his
colleagues (Glass, 1977; Glass, McGaw, & Smith, 1981), we used the
pooled standard deviation because it provides a better estimate of the
population standard deviation (Hedges, 1981). Furthermore, in some
studies a standard deviation specific to the comparison group was not
reported, although the pooled within-group standard deviation could
be derived from other statistics.
In many cases, dcould not be computed from the means and standard
deviations, as suggested by the abovementioned formula, because this
information was not provided in the study. When either of these statis-
tics was not provided, the effect size was estimated through a variety of
techniques (see, e.g., Glass et al., 1981, chap. 5). For instance, if the
difference between only and non-only children was tested by a t test, the
effect size was calculated as follows:
d=t~-~ nzl"
In studies reporting nonparametric statistics (e.g., chi-~uares), the
statistic was transformed to a corresponding t ratio and then into an
effect size. Whenever tests of statistical significance were performed but
the actual statistics were not reported, a probability value of .05 was
assumed if the results were reported as significant. When the group
difference was reported as nonsignificant, the effect size was conserva-
tively estimated as zero.
Given the diverse sample sizes of the studies included in these recta-
analyses, the effect sizes were computed two ways, weighted and un-
weighted by sample size. We took this approach because an effect size
computed from a study with a large sample should be more reliable
than one from a study with a small sample (Hedges, 1981).
Many studies reported comparisons for more than one outcome. Sep-
arate effect sizes were computed when the outcomes were in different
areas, as defined in Table 2. For example, a study may have included IQ
as well as teacher ratings of citizenship. Because these two variables were
categorized as character and intelligence, respectively, the effect size rep-
resenting each was considered separately within each category. How-
ever, when multiple outcomes from the same study were in the same
category (e,g., both verbal and quantitative ability measures) a d was
calculated for each measure separately and then averaged. This averag-
ing ensured that each study contributed only one effect size per compar-
ison per topic, thereby avoiding the problem of underestimating error
variance (see Glass et al., 1981, chap. 6).
Care was taken to make the direction of the effect size uniform in
meaning within each topic area. Effect sizes were always computed so
that a positive number indicated the presence of a desirable attribute or
the absence of an undesirable attribute for only children. That is, a posi-
tive dindicates that the only children had more desirable characteristics
than the non-only children, and a negative d means the reverse.
Intervening Variables
The studies were examined to determine what information was
broadly available to measure historical and maturational factors. The
year of publication was selected as reflecting historical factors and the
age group of the subjects was selected as reflecting their maturational
level. These two variables were correlated with the effect sizes compar-
ing only borns to all others within each of the five developmental out-
Explanatory Mechanisms
Two of the three explanatory mechanisms were tested by the results
of the five meta-analyses of developmental outcomes. Within each de-
velopmental outcome, support for the deprivation mechanism would be
found if only borns were at a significant disadvantage compared with
others. Support for the uniqueness of only children would be found if
only borns were different from all others; that is, if no comparison group
was found to be similar to only children.
The third explanatory mechanism, the parent-child relationship, was
tested in two ways. First, indirect support for this mechanism would be
found if the developmental outcomes of only borns were consistently
indistinguishable from those of firstborns, but distinguishable from oth-
ers. That is, if the effect sizes comparing only and firstborns were not
significantly different from zero across the five developmental outcomes,
and if the effect sizes comparing only to other borns were significantly
different from zero, then indirect support for the parent--child relation-
ship mechanism would be found.
Second, this mechanism was more directly tested by a meta-analysis
of studies that compared the parental relationships of only children to
those of non-only children. Nineteen studies focused on the nature of
the parent-child relationship and compared only borns to others. These
studies included those involving teenagers' descriptions of their rela-
tionships with their parents, parents' ratings of their relationship with
their children, and observers' evaluations of the degree of positive con-
tact between mother and child. These studies were coded such that
higher scores represented positivity.
Direct support for this mechanism would be found if a specific pat-
tern of results was obtained. That is, if only borns were found to have
developmental outcomes than others, and if these meta-
analyses indicated that only borns have more desirable parent-child re-
lationships than others, then it could be argued that the desirable par-
Mean Effect Sizes for Developmental Outcomes:
Only Children Compared With Others
Only children No. of
compared to: studies
Effect size
All non-only borns 43 .17"* .25
Small families 20 -.07 .17
Medium families 22 .11" .2 l
Large families 20 .44** .56
Firstborns 21 .06 .17
Later borns 23 .20** .25
All non-only borns 39 .03 .26
Small families 14 .03 .17
Medium families 13 .08 .16
Large families 12 .11 .23
Firstborns 16 .01 .19
Later borns 19 .04 .20
All non-only borns 26 .14** .24
Small families 10 .06 .17
Medium families 7 .24* .18
Large families 6 .33* .28
Firstborns 14 .12 .21
Later borns 16 .14 .29
All non-only bores 41 .17** .16
Small families 29 .03 .18
Medium families 30 .14** .18
Large families 25 .43** .33
Firstborns 17 .01 .12
Later borns 17 .17"* .16
All non-only borns 30 -.04 .29
Small families 11 -.04 .30
Medium families 11 -.08 .24
Large families 10 -.05 .34
Firstborns 15 .04 .30
Later borns 15 -.02 .43
Note. The numbers of studies contributing to the effect sizes vary be-
cause most studies did not compare only borns to all family sizes and
birth orders. A positive effect size means only borns surpassed non-only
borns. A negative effect size means that non-only borns surpassed only
*p < .05, two-tailed. **p < .01, two-tailed.
topic, there is an overall mean effect size, representing the com-
parison between only borns and all non-only borns. A positive
mean indicates that only borns surpassed non-only borns; a
negative mean indicates that the comparison group surpassed
the only borns. This is followed by mean effect sizes represent-
ing the comparisons between only borns and persons from
small, medium, and large families and between only borns and
first- or later borns. Here too, a positive mean indicates that
only borns surpassed the comparison group.
We conducted t tests on the mean effect sizes to determine
whether they were reliably different from zero. In order to
toughen the standards for accepting the hypothesis that there
was a reliable difference, we used two-tailed tests. In addition,
attention was paid to the probability level associated with each
t. All but 3 of the 11 effect sizes found to be reliably different
from zero were at thep < .01 level, two-tailed. These three were
at the p < .05 level, two-tailed. In contrast, the nonsignificant
mean effect sizes were not even close to reaching p = .05. In-
stead, these ts were associated with probability levels of .50,
Developmental Outcomes
Note that for both achievement and intelligence, the compar-
isons between only borns and all non-only borns, between only
borns and people from medium and large families, and between
only and later borns produced mean effect sizes reliably differ-
ent from zero. In these comparisons, only borns had more posi-
tive developmental outcomes than the comparison group. The
other comparisons, those between only borns and people from
small families and between only and firstborns, were not relia-
bly different from zero for any of the outcomes examined.
In terms of character, the effect sizes for the comparisons be-
tween only and all non-only borns and between only borns and
people from medium and large families were positive and sig-
nificant, indicating that only borns had more desirable person-
alities. The other character comparisons were not reliably
different from zero.
Not one of the sociability or adjustment means was reliably
different from zero, suggesting that only borns were as sociable
and adjusted as others.
ent-child relationship was a likely cause of the developmental outcome.
However, if only borns are found to have undesirable outcomes, and
their parent-child relationship is found to be undesirable, then it would
be uncertain whether sibling deprivation or a negative parent-child rela-
tionship brought about this effect. Of course, if the parent-child rela-
tionships of only borns are not significantly different from those of oth-
ers, then it is unlikely that this mechanism contributes to any develop-
mental outcome differences.
The effect sizes were computed both weighted and un-
weighted by sample size. The pattern of results was comparable
whether the effect sizes were weighted or unweighted. In order
to be brief, we report only the unweighted effect sizes.
Table 3 presents the mean effect sizes and their standard devi-
ations for the five developmental outcome topics. Within each
Parent-ChiM Relationship
Table 4 presents the results for the meta-analysis of the litera-
ture on parent-child relationships. The effect size representing
the overall comparison between only and non-only borns was
reliably different from zero, indicating that only borns had
more positive relationships with their parents than did others.
The effect size representing the comparison between only borns
and people from large families was also reliably different from
zero, suggesting that the only child advantage may be greatest
in comparison to people from families with five or more chil-
dren. All other effect sizes were not reliably different from zero.
Intervening Variables
Correlation coetficients between the only/all non-only effect
sizes and two intervening variables (year of publication and the
Table 4
Mean Effect Sizes for Parent-Child Relationships:
Only Children Compared With Others
Effect size
Only children No. of
compared to: studies
All non-only bores 19 .15* .20
Small families 12 .06 .10
Medium families 12 .10 .17
Large families 12 .20* .20
Firstborns 7 .08 .12
Later borns 6 .07 .26
The numbers of studies contributing to the effect sizes vary be-
cause most studies did not compare only bores to all family sizes and
birth orders. A positive effect size means only bores had more positive
relationships than non-only bores.
*p < .01, two-tailed.
subjects' age group) were computed for all topics. Only three
were significant. The year of publication was significantly asso-
ciated solely with the effect size in the intelligence area. This
correlation, r = -.41, p < .05, indicates that studies published
closer to 1925 (the publication year of the oldest study) had
effect sizes more favorable to only borns than did studies pub-
lished more recently.
Age group wad significantly correlated with effect sizes in the
achievement and intelligence areas. In achievement, this corre-
lation, r = .26, p < .05, indicated that the only born advantage
was greater for older than for younger individuals. In intelli-
gence, this correlation, r = -.36, p < .05, indicated that the only
born advantage was greater in younger than in older individuals.
Table 5 presents the mean effect sizes by age group. Note that
for both intelligence and achievement, all mean effect sizes are
positive, indicating an only child advantage across all the age
groups represented. For achievement, the mean effect sizes at
the college age to adult levels are reliably different from zero,
whereas the mean effect sizes for the younger ages are not. This
may reflect the small number of studies containing younger sub-
jects. For intelligence, the reverse pattern is found, and the mean
effect sizes for the youngest three age groups are reliably differ-
ent from zero. The mean effect sizes for the older groups are not
reliably different from zero, but few such studies are repre-
sented here.
Measurement Type
Finally, the effect sizes were divided within topic into those
produced from self-reported data and those produced from
other-reported data (e.g., professional diagnoses, peer ratings).
We performed t tests to compare the mean effect sizes produced
from self- versus other-reported data. Because the intelligence
area consisted solely of self-reported data, it was excluded from
these analyses.
The results indicated that one area, sociability, produced a
significant t(29) = 2.77, p < .05. The mean for self-reported
data (-. 15) was reliably different from zero and negative, indi-
cating that only borns rated themselves as less sociable than
non-only borns rated themselves. In contrast, the mean for the
other-reported data (. 11) was not reliably different from zero
and positive, indicating that only and non-only borns were
equally likely to be rated as sociable by others (mostly peers).
This discrepancy probably caused the sociability mean effect
sizes reported in Table 3 to not be reliably different from zero
because these means contained both types of data.
The results of these meta-analyses suggest that the popular
and negative views about only children are not valid. Across the
five developmental outcomes we considered, only borns were
not found to be at a significant disadvantage relative to their
peers with siblings.
Explanatory Mechanisms
The results can also be used to evaluate the three explanatory
mechanisms that have been used in the literature to explain
only child development. Of these three only one received sup-
Overall, the meta-analysis results tend to discredit the depri-
vation mechanism. With respect to achievement and intelli-
gence, the results suggest that growing up without siblings is an
advantage, particularly in comparison to those who grow up
with several or older siblings. The tendency for some researchers
to explain differences between only borns and others in terms
of sibling absence would be appropriate only if sibling presence
is portrayed as a suppressor, rather than an enhancer, of develop-
ment. Furthermore, proponents of a deprivation explanation
have argued that lack of siblings leads to inadequate character
development. Instead, our results indicate that the absence of
siblings is not a handicap, especially when only borns are com-
pared with people from medium and large families.
The results of the meta-analyses also contradict the only child
uniqueness mechanism. That is, only borns were not found to
Table 5
Mean Effect Sizes by Age Group for Achievement
and Intelligence Outcomes
Outcomes, Effect sizes, No. of
age group M studies
Preschool -- 0
Grammar .07 5
K- 12 combined .02 4
Jr. and Sr. high .16 11
College .21 * 9
Adult .23* 14
Preschool -- 0
Grammar .21" 11
K-12 combined .26* 9
Jr. and Sr. high .14" 10
College .07 7
Adult .04 3
Effect sizes represent the comparison between all non-only versus
all only borns.
* p < .05, two-tailed.
be distinct from all others. They were consistently similar to
firstborns and people from small families. That is, across the
areas of achievement, intelligence, sociability, character, and
adjustment, only borns were not reliably different from first-
borns or those from small families (i.e., two-child families).
Both direct and indirect support was found for the parent-
child relationship mechanism. Recall that direct support for
this mechanism would consist of a specific pattern of results:
(a) only borns would be found to have more positive relation-
ships with their parents than others and (b) only borns would
be found to have more positive developmental outcomes than
others. This pattern was obtained, suggesting that the more pos-
itive relationships only borns have with their parents contribute
to their more desirable developmental outcomes.
Indirect support came from the finding that across all meta-
analyses on the developmental outcomes, only and firstborns
were never found to be significantly different from each other.
Recall that both only and firstborns are their parents' first child
and, at least for a while, both are the only child.
In summary, these results suggest that only children do not
experience a developmental disadvantage because they lack sib-
lings. Further, the outcomes of only children are indistinguish-
able from those of firstborns or people with one sibling. Finally,
the developmental advantages of only borns may be due to the
nature of their relationships with their parents. Because the par-
ent-child relationship mechanism seems critical in explaining
only child development as well as firstborn and two-child family
development, we shall elaborate on it.
Parent-Child Relationship of Firstborns and People
From Small Families
The results of the quantitative review suggest that the mecha-
nisms that bring about only child outcomes are not limited to
only children, but rather are also at work in bringing about
firstborn and small-family outcomes. We argue that these
groups share a specific type of relationship with their parents,
one that is characterized by heightened anxiety and attention.
Further, we argue that parental anxiety motivates parents to
have high-quality interactions with their children. This, in con-
junction with the tendency for such parents to have more time
to attend to their children, means that their children are more
likely to experience greater quantities of high-quality parent-
child interactions. In turn, these interactions are thought to
bring about the developmental outcomes found here. We de-
scribe the anxiety and attention factors in more detail next.
There is little doubt that parents with one or two
children are initially more anxious about their children than are
more experienced parents. Research documenting that tension
and anxiety generally accompany the transition to parenthood
is extensive (e.g., Dyer, 1963; Hobbs & Cole, 1976; Leifer, 1980;
Miller & Sollie, 1980).
It has been argued that this heightened anxiety affects the way
parents approach childrearing. For example, Schachter (1959)
hypothesized that this anxiety motivated parents to react
promptly to their child's behavior, and this greater responsive-
ness was thought to make the child more affiliative in times of
stress. Wrightsman (1960) originally supported this prediction
and his finding was replicated in field studies (Hoyt & Raven,
1973) as well as with role-playing techniques (Greenberg,
More recently, Falbo (1984) posited that this enhanced pa-
rental vigilance may encourage the development of an internal
locus of control in only and firstborns. That is, the development
of an internal locus of control may he facilitated by parents who
respond quickly to their children's behavior. Such children are
more likely to develop the belief that their behavior causes their
parents' reactions than are children whose behaviors go unno-
ticed and therefore unrewarded or unpunished. Both only and
firstborns have been found to have a more internal locus of con-
trol than do later borns (Crandall, Katkovsky, & Crandall,
1965; Falbo, 1981; MacDonald, 1971) and this may have con-
tributed to the results we found for character.
Inexperience in childrearing also might lead parents to have
higher expectations for their children than are realistic. For ex-
ample, first-time parents underestimate the time it takes for a
child to be toilet trained, speak a complete sentence, or sleep
continuously through the night (Waddell & Ball, 1980). There
is evidence that parents maintain these heightened expectations
about their children beyond this early period (Clausen,
Kammeyer, 1967). Such heightened parental expectations may
facilitate the development of achievement motivation in chil-
dren in that achievement motivation is thought to arise from
parents placing high standards on their children at relatively
early ages (Winterbottom, 1958). In other words, parental inex-
perience may facilitate the development of achievement motiva-
tion in firstborns and people from small families. This achieve-
ment motivation, combined with other factors we shall de-
scribe, probably accounts for the greater achievements of only
children, firstborns, and children from small families.
Furthermore, for parents of only children, it seems plausible
that the recognition that their child is the only one they will ever
have motivates them to establish and maintain positive relation-
ships with their child and to encourage achievement. The re-
suits of the meta-analysis on parent-child relationships support
the position that only children and their parents have good rela-
tionships. The positivity of this relationship may help to temper
the high parental expectations so that the child can establish a
positive self-image while still reaching for higher achievement.
First-time or two-child parents have more time to
spend with each child than do parents with more children.
Mercy and Steelman (1982) have argued that family size con-
strains both the amount of time parents have for each child and
the type of activities they engage in with that child. Similarly,
others have suggested that families of varying sizes provide
differential learning environments, which mediate developmen-
tal outcomes (Marjoribanks, 1976a, 1976b).
From this perspective, one would expect first-time or two-
child parents to have more opportunity to spend one-on-one
time with their children. The results of several studies support
the position that only borns (including those who later become
firstborns) may receive more attention than other children. For
example, Falbo and Cooper (1980) found that mothers spent
more time with their preschool-aged only children during a typ-
ical week than did mothers with more children. Furthermore,
there is evidence that the quality of this parental time is higher
in one-child than larger families. Lewis and Feiring (1982)
found that during family meals, one-child families engaged in
more parent-child conversations with more information ex-
change than did families with two or three children. This
greater parental attention and involvement with the only child
has been reported by several investigators of early childhood
(Gewirtz & Gewirtz, 1965; Hilton, 1967).
This enhanced parental attention probably aids the child in
acquiring more sophisticated intellectual skills, such as vocabu-
lary, as well as more mature behavior patterns. Both of these
characteristics probably help only children score higher on tests
of intellectual ability and character than children from larger
The additional time that parents have probably aids the
child's social development in that parents of one child are more
likely to have the time to support their child's participation in
extracurricular activities and health care. Indeed, there is evi-
dence that only borns are more likely to participate in extracur-
ricular activities in high school than are others (Claudy, 1984).
This greater extracurricular engagement of only borns is also
facilitated by the tendency for only borns to do fewer household
chores than others (Polit, 1984). Furthermore, there is evidence
that the greater financial and time resources of parents of only
children aids the health care of only children. For example,
Howe and Madgett (1975) examined the records from a mental
health clinic and found that over a 15-year span, only borns did
not differ from non-only borns on reasons for being referred,
but their parents were twice as likely to bring them back for
repeat visits. Thus, health problems manifested by only chil-
dren may be more likely to receive full treatment than are sim-
ilar problems of non-only children.
Finally, the similarity between only borns and firstborns have
been repeatedly emphasized by investigators in the birth order
field. Although the early experiences of only borns and first-
borns are similar, the similarity ends abruptly for firstborns
when their first sibling is born. Despite being dethroned, first-
borns are thought to maintain a special status with their parents
(Kidwell, 1978; Schachter, 1959) and we argue that this influ-
ences the parent-child relationship in ways facilitating the de-
velopment of achievement, intelligence, and character.
Likewise, the results of the recta-analyses on development
outcomes suggest that the parent-child relationship mecha-
nism functions similarly for the one- and two-child family. That
is, these results suggest that significant diminutions of parental
anxiety and attention come only after the birth of the third
child. Because parents of three or more children have acquired
more childrearing experience and have many more demands on
their time, their later-born children are less likely to have the
experiences conducive to intellectual development and achieve-
ment than are firstborns or children from smaller families.
Children from larger families are also less likely to have rela-
tionships with parents that are conducive to the development of
an internal locus of control or leadership, both characteristics
representing character in this review. That is, parents with sev-
eral children generally do not have the energy or time to moni-
tor closely the conduct of each child. In addition, children from
larger families would be expected to follow the leadership of
their parents or older siblings rather than learn how to exercise
their own. This is consistent with the findings that parents in
large families are more likely to use an authoritarian form of
control (Bossard & Boll, 1956; Clausen, 1966).
Alternative Mechanisms
Some may argue that the parent-child relationship mecha-
nism may be merely a proxy for the true causal mechanism at
work in these developmental outcomes: parent characteristics.
That is, it could be argued that only children and similar others
(firstborns and those from two-child families) have good rela-
tionships with their parents and better developmental outcomes
because they are more likely to have parents with superior char-
This alternative explanation works well in accounting for the
positive outcomes of people from small families. For example,
Blake (198 l) reported that based on annual nationwide surveys
from 1972 to 1978, the parents of one or two children had more
education than parents of larger families. Thus, the finding that
people from small families achieve more than people from large
families may simply reflect the fact that they are more likely to
have better educated parents who transmit their pro-education
and achievement values to their children.
Further, one could argue that the educational attainment of
parents is merely a proxy variable for their intelligence. It has
been repeatedly found that education is inversely related to fer-
tility (Bumpass & Westoff, 1970; Westoff& Ryder, 1977). Re-
search conducted on a nationwide sample of urban whites has
also found that women with higher IQs have fewer children than
women with lower IQs (Udry, 1978). Thus, it may be that the
greater intelligence and achievement of children from small
families may be caused by the greater intelligence and education
of their parents. That is, bright people may be more likely to
rear children in ways facilitating their achievement and intellec-
tual development than dull people. Furthermore, it could be ar-
gued that genetic factors contribute to the developmental ad-
vantages of children from small families. Therefore, the devel-
opmental outcomes of people from small families may be
caused by their inheritance and their parents' competence and
values and not by the nature of the parent-child relationship,
as described previously.
Although this alternative mechanism has some merit, it does
not explain why only children were found to be indistinguish-
able from firstborns. All parents have a firstborn, regardless of
the parents' educational, intellectual, or genetic characteristics.
Thus, the developmental advantages we found cannot be dis-
missed entirely as due to an abundance of superior parental
characteristics among small families because firstborns share in
these advantages.
Rather, we argue that the parent-child mechanism is the
most parsimonious explanation for our results because it ac-
counts for the similarities among only borns, firstborns, and
people from a two-child family. However, if this similarity is
brought about by multiple causes, then one could argue that
the developmental advantages of only children, firstborns, and
people from small families may be caused both by their rela-
tionships with their parents and the superior characteristics of
their parents. That is, the relationship between parents and their
firstborns may nurture their achievement and intellectual devel-
opment so that their outcomes resemble those of children from
small families.
Intervening Variables
We described two types of temporal variables in the introduc-
tion as potentially intervening between the explanatory mecha-
nism and the developmental outcome. One of these reflected
historical events outside the family and the other reflected mat-
urational changes within the individual.
Historical changes. The year of publication was the only his-
torical variable consistently available within the studies in-
cluded here, and it was significantly related solely to the effect
size for intelligence. This correlation suggested that only chil-
dren born just before or during the Great Depression seemed
to benefit more intellectually from being an only born than did
only children born more recently, during more affluent times.
We argue that only borns benefit especially during times of
economic hardship because they can receive the full measure of
whatever resources their families have. Individual children
from medium and large families are likely to receive less finan-
cial support than do only children, and the effects of this relative
deprivation would be more severe during times of economic
scarcity. Although it seems plausible that lack of adequate fi-
nancial support adversely effects several areas of development,
only the connections between economic hardship, malnutri-
tion, and stunted intellectual development have been clearly es-
tablished (Loehlin, Lindzey, & Spuhler, 1975). Therefore, it is
not surprising that none of the other developmental outcomes
yielded significant correlations between effect sizes and year of
Maturational changes. In two areas, achievement and intelli-
gence, the age of the subjects was significantly related to the
effect sizes. In achievement, the only child advantage was found
to increase as the child aged. This may reflect the fact that
achievement measures of older subjects (e.g., educational at-
tainment) are more reliable than are those of younger subjects
(e.g., grades) or the fact that there were more studies of the
achievement of older subjects.
Alternately, this may be due to the tendency for parental in-
come to increase over time, thereby allowing parents to devote
more income to their children as they are launched from the
family. One consequence of having just one child is that this
child can receive the entire benefit of the increased income. Fur-
thermore, a family's having more income may help older chil-
dren more than younger children. That is, public schooling is
available to all children, but college and graduate training is
not. Therefore, only borns may benefit more than other chil-
dren from the enhanced financial resources of their family over
time. This probably improves their chances of obtaining higher
educations and other specialized experiences (e.g., summer
camps for athletic training) conducive to achievement. Like-
wise, this means that the only child is more likely than others
to receive the material objects he or she needs to feel accepted,
such as clothing or musical instruments.
In intelligence, the reverse relation was found between effect
sizes and age. The intelligence advantage of only borns was
smaller among older than younger subjects. This may reflect the
fact that relatively few intelligence studies contained adult sub-
jects. Alternatively, this age shift may reflect the maturational
changes described by the confluence model (Zajonc & Markus,
1975). Stated simply, the confluence model hypothesized that
only children score higher than others in early childhood, but
that this advantage declines and reverses during adolescence,
when siblings serve as intellectual resources for each other.
Thus, the model would predict that the effect sizes comparing
adolescent and older only children to others would be negative.
The intelligence results do not support the confluence model
because not one of the comparisons between only children and
others was negative. Nonetheless, the decline in the only child
advantage with age is somewhat consistent with the model's pre-
None of the mean effect sizes in the area of sociability was
reliably different from zero. However, additional analyses in this
area indicated that the method by which sociability was mea-
sured was significantly related to the relative sociability of only
borns. That is, when the sociability data were based on self-
reports (e.g., need for affiliation scales), only borns scored lower
than others. In contrast, when the sociability data were based on
the evaluations of others (e.g., peer ratings), only borns scored as
high as non-only borns.
This discrepancy can be explained in two ways. First, because
only borns may spend more time alone or in the presence of
adults than do other children, they may acquire preferences for
more mature activities, such as reading or stamp collecting.
There is evidence supporting this interpretation. For example,
based on a survey of 3,221 high school students conducted in
1960, Claudy (1984) reported that only borns spent more time
in solitary, intellectual and artistic activities and less time in
group-oriented and practical activities than did their peers with
Second, Connors (1963) explained the lowered need for
affiliation among only borns as being caused by the relatively
large amounts of affection they receive from their parents. Be-
cause of the undiluted parental affection only children receive,
Connors posited that they were less motivated to affiliate with
others. Thus, the self-reported lowered sociability of only borns
may reflect their acquired activity preferences and/or their close
ties to their parents. Regardless of the cause, the preponderance
of evidence suggests that only borns do not suffer as a conse-
quence of their self-reported lowered sociability. For example,
they do not rate themselves as lonelier than do others (Falbo,
1981) nor do they have lowered levels of self-esteem (Falbo,
Summary. The results of our meta-analyses contradict the
theoretical notions that only children are deprived or unique.
In achievement, intelligence, and character, only borns excelled
beyond their peers with siblings, especially those with many or
older siblings. Furthermore, across five developmental out-
comes, only children never differed significantly from firstborns
or people from two-child families. The nature of the parent-
child relationship was supported as contributing to these devel-
opmental advantages in firstborns and children from one- and
two-child families. In such families, enhanced parental atten-
tion and anxiety were seen as facilitating the development of
achievement, intellectual ability, and character.
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Revision received January 30, 1986 9
... For the impoverished students' families, social support is an effective way for to relieve financial stress (Zheng, 2021). Besides, the perspective of different treatments by parents suggest OCs may differ from NOCs in individual's adaptability, behavioral patterns, and physical and mental health (Falbo and Polit, 1986;Kolm and Ythier, 2006;Minuchin, 2018;Wang and Yuan, 2019). Thus, this study focuses on the moderating effect of OC on the relationship between social support and mental health. ...
... OC and NOC families exist in China (Li et al., 2018). The parenting styles and upbringing in OC and NOC families affect individuals' adaptive capacity, behavior, and physical and mental health differently (Falbo and Polit, 1986;Kolm and Ythier, 2006;Minuchin, 2018;Zheng et al., 2019). Research has identified that differences exist in personality, character, and resources between individuals from OC and NOC families (Falbo and Polit, 1986;Cameron et al., 2013;Wang and Yuan, 2019). ...
... The parenting styles and upbringing in OC and NOC families affect individuals' adaptive capacity, behavior, and physical and mental health differently (Falbo and Polit, 1986;Kolm and Ythier, 2006;Minuchin, 2018;Zheng et al., 2019). Research has identified that differences exist in personality, character, and resources between individuals from OC and NOC families (Falbo and Polit, 1986;Cameron et al., 2013;Wang and Yuan, 2019). OCs may lack communication skills, an ability to cooperate (Minuchin, 2018), and an awareness of competition and display a strong tendency toward risk aversion (Cameron et al., 2013;Wang and Yuan, 2019). ...
Full-text available
According to the hardiness model and the perspective of different treatment by parents, this study developed and validated a moderated mediation model to explore the direct effect of hardiness on the mental health of Chinese funded college students (FCSs), the mediating role of social support, and the moderating role of only-child (OC) /non-only-child (NOC) status. A hardiness scale, mental health scale, and perceived social support scale were used to examine information on 673 Chinese FCSs. Hardiness had a significantly positive effect on the mental health of FCSs. Mediation analysis indicated that social support mediated the relationship between hardiness and the mental health of FCSs. The moderated mediation model analysis indicated that the OC/NOC status moderated the second half of the mediation model. The results suggest that the hardiness model is applicable to FCSs from China and elucidate the internal influence mechanism between hardiness and mental health. On the basis of the findings of this study, suggestions are presented in this paper for college education management.
... One of the most profound early-life experiences is growing up with siblings (Falbo and Polit, 1986;Feng, 2000;Cameron et al., 2013); however, a large number of only children are deprived of such an experience. It is estimated that there were over 220 million only children in mainland China at the end of 2015 (Li et al., 2018); moreover, the number of American women who decided to have only one child doubled from 11% in 1976 to 22% in 2015 (Gibson, 2019). ...
... How the unique family experience of being an only child shapes their power acquisition remains unclear. Researchers have found that only children are overrepresented among incumbents in political office (Andeweg and Berg, 2003;Reitan and Stenberg, 2019), whereas others have revealed that only children adapt poorly to social activities (Kitzmann et al., 2002) or have lower self-rated sociability (Falbo and Polit, 1986). Given that the number of single-child families is continuing to increase (Feng, 2020), explorations on the influence of only child status on power acquisition are needed. ...
... Finally, identifying the moderating effect of dependency on parents can help us to understand whether sibling and child-parental relationships interactively influence individual behaviors. Child-parental relations and sibling relations were identified as two key mechanisms to explain the behavioral pattern of the only child (Falbo and Polit, 1986;Reitan and Stenberg, 2019), yet their interactive relationships were rarely considered. We demonstrate that siblings and parents are two sources of socialization and the effect of sibling deprivation (being an only child) is conditioned upon the childparental relations. ...
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Drawing upon a developmental perspective, we investigated the differences in power acquisition (i.e., rank at work and leader role occupancy in university) between only and non-only children as well as the mediating role of cooperative and competitive orientations and the moderating role of dependency on parents. To test our hypotheses, we conducted two field studies in 155 part-time Master of Business Administration (MBA) students (Study 1) and 375 senior students (Study 2). Results showed that: (1) non-only children were more likely to achieve higher rank at work than only children; (2) only children were less likely than non-only children to acquire power in organizations because they scored lower in cooperative orientation; however, the mediating effect of competitive orientation was not significant; (3) the difference in cooperative orientation between only and non-only children was smaller when dependency on parents was high, whereas it became larger when dependency on parents was low. Our research contributes to the understanding of how family structure influences individual power acquisition.
... those with no biological siblings) have so far been underexplored. While scholars have long been interested in how only children may be different to those with siblings, the majority of the literature has focused on shortterm developmental and cognitive outcomes in early life or adolescence (Blake 1981;Falbo and Polit 1986;Mancillas 2006;Falbo 2012), rather than on health. The question of health deserves further attention, given that only children constitute a substantial subgroup of all sibship groups in highincome, low-fertility settings (Frejka et al. 2008;Präg et al. 2020). ...
... Parents of only children likely include a subset whose fertility desires were interrupted due to partnership disruption or health reasons, which might also negatively influence child outcomes. Only children are more likely to live in one-parent households, both in the US (Falbo and Polit 1986;Datar 2017) and the UK (Sheppard and Monden 2020). In Sweden only children are more likely to be the offspring of divorced or separated parents (Andersson 1997), a situation which is itself Figure 1 Percentage of children by biological sibling group size in the family of origin: men and women born in Sweden, 1940-95 associated with a range of negative offspring social and health outcomes (Amato and Keith 1991;McLanahan et al. 2013;Turunen 2014;Goisis et al. 2019). ...
... Overall, this body of research has repudiated the negative stereotype of only children. Several reviews and meta-analyses have suggested that only children do not have intellectual or developmental disadvantages in early life; indeed, in some domains they seem to do better than children with siblings (Falbo and Polit 1986;Polit and Falbo 1987;Falbo 2012). An educational and social advantage for only children has also been found in studies from China, where the one-child policy may be considered an exogenous shock on family size (Poston and Falbo 1990;Chen and Goldsmith 1991;Falbo and Poston 1993;Falbo 2012). ...
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Only children (with no full biological siblings) are a growing subgroup in many high-income settings. Previous studies have largely focused on the short-term developmental outcomes of only children, but there is limited evidence on their health outcomes. Using Swedish population register data for cohorts born 1940-75, we compare the health of only children with that of children from multi-child sibling groups, taking into account birth order, family size, and presence of half-siblings. Only children showed lower height and fitness scores, were more likely to be overweight/obese in late adolescence, and experienced higher later-life mortality than those with one or two siblings. However, only children without half-siblings were consistently healthier than those with half-siblings, suggesting that parental disruption confers additional disadvantages. The health disadvantage was attenuated but not fully explained by adjustment for parental characteristics and after using within-family maternal cousin comparison designs.
... Data on age, sex, ethnicity, hometown region, school type, average monthly expenditure, sexuality education at school, self-rated parent-child relationship, parents' highest educational qualifications, and parent-child discussion relevant to sexual behaviors/contraception, and tobacco and alcohol use were also collected. These factors have been demonstrated by published literature to have impact on SRH outcomes or to contribute to the difference between the only-child students and students with siblings (22)(23)(24). ...
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Objective The differences in sexual knowledge, attitudes, behaviors, seeking behaviors for sex-related knowledge, and sexual and reproductive health (SRH) outcomes among only-child students and students with siblings in China, was examined for sex- and region- specific effects. Research Design and Methods Data on 49,569 students from the 2019 National College Student Survey on Sexual and Reproductive Health, conducted across 31 provinces in mainland China was utilized. Multivariable regression and stratified analyses were employed to analyze the differences in sexual and reproductive health between only-child students and students with siblings. Results Only-child students reported higher sexual knowledge, more liberal sexual attitudes, and fewer adverse SRH outcomes compared to those with siblings. Results were found to be influenced by sex and hometown region after controlling for socio-economic factors, parent-child relationship, and sexuality education. Conclusions Female students with siblings who resided in rural regions were more likely to have poorer SRH compared to male only-child students who resided in urban regions. Comprehensive sexual education for students should aim to better include females and students from rural areas both offline and online, and public healthcare should offer subsidized consultations and contraceptives.
... Further, studies comparing only children to those with siblings suggest that patterns differ depending on the outcome and context investigated (see e.g. Choi & Monden, 2019;Falbo, 2012;Falbo & Polit, 1986;Mancillas, 2006;Polit & Falbo, 1987). In fact, for some health outcomes, including BMI as discussed above (Meller et al., 2018), the lack of siblings is associated with worse outcomes. ...
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Only children, here defined as individuals growing up without siblings, are a small but growing demographic subgroup. Existing research has consistently shown that, on average, only children have higher body mass index (BMI) than individuals who grow up with siblings. How this difference develops with age is unclear and existing evidence is inconclusive regarding the underlying mechanisms. We investigate BMI trajectories for only children and those with siblings up to late adolescence for four British birth cohorts and across adulthood for three cohorts. We use data on BMI from ages 2 to 63 years (cohort born 1946); 7 to 55 years (born 1958); 10 to 46 (born 1970) and 3 to 17 years (born 2000-2002). Using mixed effects regression separately for each cohort, we estimate the change in BMI by age comparing only children and those with siblings. The results show higher average BMI among only children in each cohort, yet the difference is substantively small and limited to school age and adolescence. The association between sibling status and BMI at age 10/11 is not explained by differential health behaviours (physical activity, inactivity and diet) or individual or family background characteristics in any of the cohorts. Although persistent across cohorts, and despite the underlying mechanism remaining unexplained, the substantively small magnitude of the observed difference and the convergence of the trajectories by early adulthood in all cohorts raises doubts about whether the difference in BMI between only children and siblings in the UK context should be of research or clinical concern. Future research could usefully be directed more at whether only children experience elevated rates of disease, for which high BMI is a risk factor, at different stages of the life course and across contexts.
... Falbo et al. reviewed research on the only child as early as 1977 and later updated this research in terms of academic achievements, personality characteristics, and social behaviors of the only child and non-only child in 2012. Falbo and Polit [3] conducted a meta-analysis of 115 studies-published between 1925 and 1984-on the only child, and found that the only child was superior to the non-only child in terms of personality characteristics such as control, autonomy, and psychological maturity, but not any social aspects. Polit [4] conducted a review of studies on the only child and personality development and found that the only child was significantly better than other groups in terms of achievement motivation and personal adaptation. ...
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Based on the data of 3561 fifth-grade and 4062 eighth-grade students from the Beijing Assessment of Educational Quality in China, the present study used a propensity-value matching model to scientifically analyze only-child and non-only-child children in primary and secondary schools. Female differences in cognitive outcomes (linguistic performance) and non-cognitive outcomes (teacher-student relationships, peer relationships, and emotional management) were also evaluated. The results of the study were as follows. First, fifth-grade only-child students had a higher linguistic performance compared to that of their non-only-child counterparts, and the same result was found for eighth-grade students. Second, fifth-and eighth-grade only-child students had good teacher-student relationships that were not significantly different from those of their non-only-child counterparts. Third-, fifth-, and eighth-grade only-child students had significantly better peer relationships and emotional management compared to these parameters in their non-only-child counterparts.
... Greater access to parental resources might explain only children's educational advantage, especially compared to children from large families, but patterns differ depending on the outcome studied and context (see e.g. Falbo and Polit, 1986;Polit and Falbo, 1987;Mancillas, 2006;Falbo, 2012;Choi and Monden, 2019). Further, the focus on childhood in existing studies raises the question of the theories' relative applicability to other stages of the lifecourse. ...
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Adult children with siblings can share caring for older parents but adult only children face this responsibility alone. Given increased longevity and reliance on informal care-giving, as well as an increase in one-child families, there is a need to investigate only children's care-giving further. Using data from three large-scale British birth cohorts, this paper investigates patterns of parent-care, care intensity and wellbeing at ages 38 and 42 (N = 17,255, N = 16,703; born 1970), 50 and 55 (N = 12,775, N = 11,339; born 1958) and 63 (N = 2,364; born 1946), how sibling composition intersects with gender in relation to care-giving and whether different care-giving patterns are associated with wellbeing. Only children are more likely to provide parent-care and the pattern is consistent with an interpretation that differences by sibling status might increase with age. Provision is gendered, and the sibling group composition matters for involvement. Although care-giving is related to wellbeing, we found no evidence that this differs between only children and those with siblings. The literature on only children has hitherto focused largely on childhood, suggesting that on some outcomes they benefit from a concentration of parental resources. Our results suggest that in middle adulthood parental care needs may instead be concentrated for the only child without the ‘resource’ of siblings. This indicates a need to develop further our understanding of this growing demographic subgroup.
... But the results are mixed. Some studies have showed that single-child is independent, highly competitive, goal oriented, academically successful and socially adjustable [1,2] whereas other studies projected singlechild as selfish, dependent, spoilt, demanding, depressed, stressed and socially maladjusted [3]. Studies on single-child in India are few and far and factors associated with it are not reported adequately, which formed the basis of this study. ...
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The rise in single child families in developing nations is considered as a new trend in population. The prevalence study for single child in Puducherry has been done as a cross sectional study involving engineering students. Along with prevalence, which was found to be 9.3, associated factors that determine single child prevalence in society were analyzed. The factors emerged important among them were parents' education, especially females' education and mothers working status. Other factors like type of family (joint family and nuclear family) and area of resident (rural and urban) were not significantly associated with the prevalence of single child in the society.