The Psychology of Gender 4th Edition

Sex-Related Comparisons: Observations 105

have sample sizes under 30, and the few stud-

ies that report women have greater verbal

skills than men are based on sample sizes of

over 100. Should we still conclude there is no

sex difference in verbal ability? The power to

detect a significant difference between women

and men when one truly exists is limited in

small samples. Thus a narrative review of an

area of research that contains many small

sample studies may lead to faulty conclusions.

In 1976, Jeanne Block wrote a response

to Maccoby and Jacklin’s (1974) review of

sex differences that was virtually ignored.

Block reviewed the same literature and ar-

rived at conclusions very different from the

ones reached by Maccoby and Jacklin. First,

she noted that Maccoby and Jacklin did not

censor the studies they included; that is, they

averaged across all studies, whether method-

ologically sound or not. A number of studies

had very small samples, a problem just noted.

Some studies used unreliable instruments;

other studies used instruments that lacked

construct validity, meaning there was not

sufficient evidence that the instruments mea-

sured what they were supposed to measure.

Second, Block (1976) noted tremendous

age bias in the studies reviewed. She found

that 75% of the reviewed studies were limited

to people age 12 and under; 40% used pre-

school children. The reason so many studies

were conducted with children is that compari-

sons between males and females first became

popular in developmental psychology. Devel-

opmental psychologists compared females and

males in their studies, hoping no differences

would be found so they could combine girls

and boys when analyzing their data. Why is it

a problem that Maccoby and Jacklin’s (1974)

review focused so heavily on children? The

problem is that they did not take into consid-

eration the fact that some sex differences might

not appear until adolescence and later; in fact,

Maccoby and Jacklin’s Psychology of Sex Differences

Maccoby and Jacklin’s (1974)Psychology of

Sex Differencesentailed a comprehensive re-

view of the ways men and women differ psy-

chologically. They examined intellectual or

cognitive domains as well as social abilities.

Their conclusions were surprising to many

people: They found that sex differences ex-

isted in only a few domains and that many

stereotypes had no basis in fact. They iden-

tified sex differences in only four domains:

verbal ability (advantage girls), visual-spatial

ability (advantage boys), mathematical ability

(advantage boys), and aggression (greater in

boys). They found no sex differences in self-

esteem, sociability, analytic ability, or achieve-

ment motivation, and it was unclear whether

there were sex differences in activity level,

competitiveness, dominance, or nurturance.

One limitation of Maccoby and Jack-

lin’s (1974) work is that it was anarrative

review. In a narrative review, authors decide

which studies are included and come to their

own conclusions about whether the major-

ity of studies provide evidence for or against

a sex difference; basically, a tally is made of

the number of studies that reports a differ-

ence versus no difference. This kind of review

presents several difficulties. One problem is

that the authors decide how many studies are

enough to show a difference does or does not

exist. If 12 of 12 studies show a difference, a

difference must exist. But what about 10 of

12? Or 8 of 12? Or even 6 of 12? How many is

enough? A second difficulty with narrative re-

views is that the pattern of results may be dis-

proportionately influenced by findings from

small samples. Perhaps the majority of stud-

ies show men and women have equal verbal

ability, but all of these “no difference” studies

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