Female adolescent contraceptive decision making and risk taking.
Johnson, Sharon A. ; Green, Vicki
Although research on the antecedents of adolescent contraceptive usage has focused on a wide variety of areas (e.g., personality and
motivation, demography), the present research concerns the
adolescent's ability to make decisions pertaining to contraceptive
use and how that ability relates to contraceptive risk taking. For a
brief review of other areas of study, see Green, Johnson, and Kaplan
(1992); for an extensive review of this literature, see Morrison (1985).
Brooks-Gunn and Furstenberg (1989) identified social cognitive
ability as a potential perspective for understanding adolescent sexual
decision making. Gordon (1990) and Cobliner (1974) identified aspects of
adolescent reasoning (formal operational thinking) as relevant to
decision making about contraceptives. The literature documents cognitive
capacity as an important factor in decision making related to
contraceptive use (Rogel, Zuehlke, Peterson, Tobin-Richards, &
Shelton, 1980; Smith, Nenney, Weinman, & Mumford, 1982). Two other
potentially related factors are adolescent cognitive egocentrism
(Cvetkovich, Grote, Bjorseth, & Sarkissian, 1975; Elkind, 1978;
Peel, 1971) and familiarity with the content domain in which the
decision is being made (Byrnes, 1988; Levine & Linn, 1977).
Green et al. (1992) examined these three factors, cognitive
(adolescent reasoning) ability, adolescent cognitive egocentrism, and
experience in contraceptive decision making (the decision to use
contraceptives), as predictors of decision making in a contraceptive use
paradigm. Fifty sexually active, unmarried females, ages 14-19, served
as subjects. Cognitive ability and cognitive egocentrism variables were
significantly predictive of several of the decision-making variables,
while the decision to use contraceptives was not found to be a
significant predictor. Forty-one percent of the variance was accounted
for in predicting the canonical decision-making variable. Green et al.
concluded that one possible reason for the nonsignificance of the
experience factor was that a single dichotomous variable was used
(using/seeking contraceptives versus not using contraceptives); a more
elaborate variable or set of variables might have yielded different
results. The literature on adolescent sexuality identifies specific
measures of sexual and contraceptive behaviors and attitudes (see Zelnik
& Kantner, 1979). These might be of value in predicting
contraceptive decision making.
A logical extension of decision making related to contraceptive use
would be to focus upon risk-taking behavior--engaging in sexual
intercourse without using contraceptives. Although no study directly
demonstrates the relationship of contraceptive use decision making to
contraceptive use risk taking, Adler, Kegeles, and Irwin (1987) showed
that adolescent behavioral intention is related to actual use of
contraceptives. Possible predictors of such risk taking have been
identified in the research literature. For example, the level of sexual
activity is positively related to contraceptive usage (Geis &
Gerrard, 1984). Also adolescents demonstrate erroneous beliefs/attitudes
about nonuse of contraceptives (Delamater & MacCorquodale, 1979;
Kantner & Zelnik, 1972). These factors may directly influence such
risk taking. Additionally, certain demographic variables (i.e., age,
gender, and ethnic status) are related to unprotected sexual activity
(Zelnik & Shah, 1983).
The present research was a modified replication of the Green et al.
(1992) study. Cognitive capacity, cognitive egocentrism, experience, and
demographic factors were examined as predictors of decision making in a
contraceptive use paradigm. Experience was assessed by two
questionnaires, one measuring sexual/contraceptive behaviors, the other
sexual/contraceptive attitudes. Additionally, the present study examined
cognitive capacity, cognitive egocentrism, experience, and demographic
variables as predictors of risk-taking behavior--nonsensible use of
contraceptives.
Predictions were as follows: Based upon the Green et al. (1992)
study, it was hypothesized that cognitive capacity and cognitive
egocentrism would be significant predictors of contraceptive decision
making. Based upon the literature pertaining to domain content (Byrnes,
1988; Levine & Linn, 1977), it was hypothesized that experience
would also be a significant predictor. There was no basis in the
literature for a prediction pertaining to age, grade, or ethnic status.
Based upon the literature (Delamater & MacCorquodale, 1979; Kantner
& Zelnik, 1972; Zelnik & Shah, 1983), it was hypothesized that
sexual/contraceptive behaviors and attitudes, age, and ethnic status
would be significant predictors of risk-taking behavior.
METHOD
Subjects
Subjects were 60 unmarried female patients, ages 14-18 years,
recruited from two adolescent medicine outpatient clinics of a large,
urban, city and county general hospital. The clinics served a lower
socioeconomic status population. All subjects tested were considered
"indigent"--that is, they were required to pay little or
nothing for medical care. All subjects were sexually active. Since it
was unclear whether prior pregnancy would influence decision making
regarding contraceptives, those who had previously been pregnant were
omitted from consideration. Thirty subjects were nonusers of
contraceptives and thirty were contraceptive users or seeking
contraceptives. One third of the subjects were white, one third were
black, and one third were Hispanic. The groups were matched on the
demographic variables of race and age. Mean age of subjects was 16.2
years.
Materials
In order to assess the level of cognitive functioning, two cognitive
tasks, Displaced Volume and PUN, were employed. Both are considered
measures of formal operational thinking. However, in a study by Jones
and Green (1991), the former discriminated between sixth graders and
those in higher grades, the latter discriminated between eighth graders
and those in higher grades. Thus, Displaced Volume would appear to
measure a lower level of cognitive functioning within formal operational
thinking than would PUN.
Displaced Volume (DV). This questionnaire included eight problems
with multiple-choice answers. Each required the subject to identify the
relevant variables and then mentally manipulate them in order to predict
their effect upon the level of water in a pictured container. (Refer to
Linn & Pulos, 1983, for further description of the questionnaire and
reliability and validity data.) A total score was calculated; a higher
number of correct responses indicated higher cognitive functioning.
Puns (PUN). This task required the subject to explain the two
meanings implied in each of three puns. One pun was: Elevator companies
have their ups and downs. An understanding of this "play on
words" type of humor required thought reversal. Responses were
coded into one of four categories: (a) response containing two quality
meanings of the pun, (b) a response containing two meanings, one or both
of marginal quality, (c) a response containing only one meaning, that
one being a quality or marginal response, and (d) an inappropriate
response or no response. A higher score indicated higher cognitive
functioning. Jones and Green (1991) have categorized the PUN responses
of 448 children (Grades 5-12). Consensus by two raters, who were experts
in the administration of psychological tests, was required to place a
response into a category. (See Jones & Green, 1991, for further
description of scoring the Puns instrument.)
Personal Fable Questionnaire (Fable). This questionnaire contained 43
items. Subjects were asked to respond to each using a Likert-type scale,
ranging from strongly agree (4) to strongly disagree (0). In a study by
Green, Morton, Starr, Jones, and Jaynes (1991), using a fifth-through
twelfth-grade normative sample, psychometric properties and factorial structure were assessed. Five factors were identified: Rejection of
Rules/Impulsivity (RU/IMP), Egocentrism (EGO), Uniqueness (UNIQ),
Magical Thinking (MAG), and Independence (IND). Twenty-five items had
salient loadings on one of these five factors. (Refer to Green et. al.,
1991, for scoring criteria, reliability and validity data, and data
related to grade and gender differences.) For four of the five factors
(not IND), high scores reflected a high level of cognitive egocentrism.
For IND, a high score reflected thoughts regarding independent action.
Five scale scores were obtained, each representing the average response
to all items loading on that factor. Since the factors were found to be
independent, no combined score was used.
Decision-Making Problem. The decision-making problem, as experienced
by another female, focused on contraceptive usage in a relationship in
which sexual intimacy was anticipated. The procedures used to
operationalize the decision-making process were designed according to a
model defined by Linn (1980). (Refer to Green et al., 1992, for a
description of the specific problem presented.) Factors listed by all
subjects were rated on a scale from very immature (1) to very mature (5)
by twelve health care professionals from an adolescent medicine clinic.
Those with mean ratings of 3 or above were categorized as mature. Seven
variables were generated from the decision-making problem: (a) the
number of variables the subject listed (NUMV), (b) the proportion of
"mature" variables listed (PRMAT), (c) the number of matches
between the variables listed by the experimenter and the subject
(MATCH), (d) the number of variables the subject used in the solution to
the problem (USEDV), (e) whether the subject used her own variables in
the solution (OWNV), (f) the number of experimenter's variables the
subject used in the solution (EXPV), and (g) the proportion of
"mature" variables used in the solution (PMUSV).
In a pilot study, two instruments were developed that measured
sexual/contraceptive behaviors and attitudes. Questions previously used
in research (Zelnik & Kantner, 1979) were used as items. Refer to
Tables 1 and 2 for lists of these items. In a factor analysis study, 42
unmarried females, between the ages of 14 and 19 years, served as
subjects. They were recruited through an adolescent medicine outpatient
clinic at a southwestern, university-affiliated health sciences center
and through introductory psychology classes at a university in the same
state. Twenty-four were sexually active and 18 were not. Of the 24
sexually active subjects, 15 used contraception (this included women
engaged in intercourse whose partners used condoms). Results from the
factor analysis are presented separately for the two questionnaires.
Sexual/Contraceptive Behaviors Questionnaire. An iterated principal
axes factor analysis scree plot of eigenvalues indicated that the
potential factor solutions ranged from 1 to 3. Principal axes factor
analysis with varimax rotation for two- and three-dimensional solutions
was applied to the numerically coded data. The most desirable solution
appeared to be the two-factor solution. The eigenvalues of the reduced
correlation for the two factors were 2.11 and 1.70, respectively.
Salience of item loadings on a factor was based upon two criteria: (a)
the loading value was .30 or greater, and (b) the difference between the
salient loading and the largest loading on the other factor was at least
.20. Four of the six items were found to have salient loadings on one of
the two factors. The two variables used represent the total score for
each of the two factors. These were labeled: (a) previous birth control
usage (SBEH1) and (b) sexual activity (SBEH2).
Sexual/Contraceptive Attitudes Questionnaire. An iterated principal
axes factor analysis scree plot of eigenvalues indicated that the
potential factor solutions ranged from 1 to 3. Principal axes factor
analysis with varimax rotation for two- and three-dimensional solutions
was TABULAR DATA OMITTED applied to the data. The most desirable
solution appeared to be the three-factor solution. The eigenvalues of
the reduced correlation for the three factors were 2.48, 1.13, and 1.00,
respectively. Salience of the item loadings on a factor was based upon
identical criteria to that specified for the Sexual/Contraceptive
Behaviors Questionnaire. Eight of the nine items were found to have
salient loadings on one of the three factors. The three variables used
represent the total score for each of the three factors. These were
labeled: (a) partner's attitudes toward contraceptive use (SATT1),
(b) myths regarding pregnancy (SATT2), and (c) subject does not want to,
or cannot, use contraception (SATT3).
TABLE 2
SEXUAL/CONTRACEPTIVE ATTITUDES QUESTIONNAIRE ITEMS
Item number Scoring Item
1 True/False When I have sex, usually have not
planned to.
2 True/False I want to use birth control but
usually I cannot.
3 True/False I want to use birth control but
usually I do not.
4 True/False I do not use birth control it
would be too costly.
5 True/False My partner does not want to use
birth control.
6 True/False My partner does not want me to
use birth control.
7 True/False I do not have intercourse
frequently enough to become
pregnant.
8 True/False I am too young to become
pregnant.
9 True/False I could not become pregnant.
Procedure
Individuals waiting for medical appointments were asked to
participate; all individuals approached agreed. Subjects were tested
individually in a private room (approximately 40 minutes). The order of
administration of the measures was PUN, Displaced Volume, Fable,
decision-making problem, and the behaviors and attitudes questionnaires.
The experimenter read the instructions for all instruments and actively
worked with each subject to insure clarification if explanations were
needed. Subjects were instructed to take as much time as necessary.
TABLE 3
SEXUAL/CONTRACEPTIVE BEHAVIORS QUESTIONNAIRE: FACTOR LOADINGS
FOLLOWING VARIMAX ROTATION FOR FOUR SALIENT ITEMS
FACTOR FACTOR LOADINGS
Item(s) 1 2
Factor 1 Previous Birth Control Usage
7 -.34 .04
8 .49 .07
9 .67 .07
Factor 2 Sexual Activity
2 .32 .76
TABLE 4
SEXUAL/CONTRACEPTIVE ATTITUDES QUESTIONNAIRE: FACTOR LOADINGS
FOLLOWING VARIMAX ROTATION FOR EIGHT SALIENT ITEMS
FACTOR FACTOR LOADINGS
Item(s) 1 2 3
Factor 1 Partner's Attitudes Toward Contraceptive Use
4 .53 .26 .18
5 .96 -.03 -.14
6 .62 -.00 .16
Factor 2 Myths Regarding Pregnancy
7 .18 .66 .22
8 -.19 .40 -.05
9 .44 .81 .22
Factor 3 Cannot/Do Not Use Contraceptives
2 .20 -.12 .86
3 .13 .15 .61
RESULTS
Multiple regression techniques were used to determine whether
decision making and risk taking could be predicted by specific
variables. Two sets of stepwise multiple regression analyses were
performed using the SAS PROC stepwise technique. In the first set, the
cognitive egocentrism, cognitive capacity, demographic,
sexual/contraceptive behaviors variables, and sexual/contraceptive
attitudes variables were used to predict the seven decision-making
variables from the contraceptive problem. One predictor variable was
found to be significant in predicting two outcome variables, NUMV
(number of variables the subject listed) and PRMAT (the proportion of
mature variables listed). Two predictor variables were found to be
significant in predicting three other outcome variables, MATCH (number
of matches between experimenter and subject), EXPV (number of
experimenter's variables used), and PMUSV (proportion of mature
variables used). Three predictor variables were found to be significant
in predicting a sixth, USEDV (number of variables used in the solution).
No significant predictors were found for one of the outcome variables,
OWNV (subject's use of own variables). See Table 5 for a summary of
these regression analyses.
The predictor variables, the outcome variable, and the percentage of
variance accounted for were as follows: (a) PUN accounted for 12% of the
variance of the outcome variable--number of variables listed, (b) PUN
accounted for 8% of the variance of the outcome variable--proportion of
mature variables listed, (c) PUN accounted for 20% of the variance and
AGE 9% of the variance of the outcome variable--number of matches
between variables listed by subject and experimenter, (d) GRADE
accounted for 15%, DV 8%, and HISP (Hispanic/non-Hispanic) 6% of the
variance of the outcome variable--number of variables the subject used
in the solution, (e) PUN accounted for 21% and GRADE 6% of the variance
of the outcome variable--number of experimenter's variables used in
the solution, (f) UNIQ accounted for 12% and IND 10% of the variance of
the outcome variable--proportion of mature variables used in the
solution.
In the second stepwise multiple regression analysis, the cognitive
egocentrism, cognitive capacity, demographic, sexual/contraceptive
TABULAR DATA OMITTED TABULAR DATA OMITTED behaviors variables, and
sexual/contraceptive attitudes variables were used to predict
SENSIB--"sensible" use of contraceptives (contraceptives used
at least 75% of the time when engaging in sexual activity). Two
predictor variables were found to be significant in predicting SENSIB.
See Table 6 for a summary of this regression analysis. The predictor
variables, the outcome variable, and the percentage of variance
accounted for were as follows: PUN accounted for 30% of the variance and
SBEH1 (previous birth control usage) accounted for 10% of the variance
of the outcome variable--SENSIB.
DISCUSSION
The hypothesis that cognitive capacity, cognitive egocentrism, and
experience would be significant predictors of contraceptive decision
making was partially supported. Cognitive capacity and cognitive
egocentrism variables were found to be significant predictors of
contraceptive decision making; however, experience, as measured by
factors from the sexual/contraceptive behaviors and attitudes
questionnaires, was not. Three demographic variables, age, grade, and
ethnic status, also were found to be significant predictors. The amount
of variance accounted for in the analyses predicting the six outcome
variables ranged from a total of 8% to 29%. Generally, the largest
amount of variance accounted for was by PUN and/or AGE/GRADE.
Additionally, DV, HISP, UNIQ, AND IND were significant predictors. The
decision-making variables with the largest amount of variance accounted
for were MATCH, USEDV, and EXPV.
Generally, these findings were similar to those in the Green et al.
(1992) study, in which cognitive capacity and cognitive egocentrism were
found to be predictive of contraceptive decision making. In the Green et
al. study, PUN was the only significant cognitive predictor of
decision-making variables. In the present study, PUN was the most common
predictor. The cognitive egocentrism variables found to be significant
predictors in the present study were different from those found in the
Green et al. study. However, in addition to the Personal Fable
Questionnaire, Green et al. used Elkind's Imaginary Audience Scale
(Elkind & Bowen, 1979). Thus, it is impossible to compare the
cognitive egocentrism results from these two studies.
Results in the present study were consistent with the literature that
subscribes to a developmental model which assumes that, as adolescents
become older, they are likely to function at a higher cognitive level.
AGE and GRADE accounted for a large proportion of the variance in
predicting the decision-making variables. However, additional variance
was accounted for by cognitive capacity. Growing older over the
adolescent period does not guarantee increased cognitive capacity. In
fact, it is a common assumption of the Piagetian model that not all
people attain formal operational thinking in the adolescent years, and
some people never achieve it (Tomlinson-Keasey, 1972).
An adolescent reasoning variable (PUN or DV) was a significant
predictor in every analysis but one. Of these two variables, PUN was the
more frequent significant predictor. This finding is consistent with the
literature which assumes that certain aspects of abstract reasoning,
such as the ability to take more than one perspective, are required for
more mature decision making and problem solving (Inhelder & Piaget,
1958; Keating, 1980; Peel, 1971).
Cognitive egocentrism variables, UNIQ and IND, accounted for
additional variance in predicting one of the decision-making variables.
UNIQ represents thinking such as, "I'm the only one in the
world who feels the way I do." IND represents thoughts regarding
independent actions, such as "I know what is best for me." The
correlation between UNIQ and PMUSV was negative; thus, greater cognitive
egocentrism was related to having used a smaller proportion of mature
variables in the solution to the problem. The correlation between IND
and PMUSV was also negative; thus, more independent thinking was related
to having used a smaller proportion of mature variables in problem
solving. The finding for uniqueness is logically consistent with the
model used; the finding for independence is not. A possible explanation
might be that subjects with more independent thought would be less
likely to care what the experimenter thought about their performance and
less likely to try to match their performance with that of the
experimenter. In fact, although not significant, the correlations
between IND and the variables of EXPV, USEDV, MATCH, and PRMAT were
negative. Notably, the only two positive correlations were those between
IND and the variables of NUMV (subject's initial listing of
variables) and OWNV (subject's use of own variables in the
solution). Further research is needed to ascertain the differential
influence of cognitive egocentrism and independence of thought upon such
decision making.
One ethnic status variable, HISP, was also found to be a significant
predictor. The correlation between HISP and USEDV was positive; Hispanic
subjects were more likely to use a greater number of variables in the
problem solution than were non-Hispanic subjects (blacks and whites).
There is no basis in the literature for interpreting this finding.
Further research is needed regarding the influence of ethnic status upon
such decision making. However, it is important to note that all subjects
in the present study were from low socioeconomic status (SES) groups.
The ethnic status finding may be limited to this SES group.
In the present study, MATCH, USEDV, and EXPV were the outcome
variables that had the largest amounts of variance predicted by
cognitive egocentrism, cognitive capacity, and demographic variables.
High scores on these three variables would require a higher level of
cognitive functioning. High scores on MATCH and EXPV would require the
subject to step back from her own perspective, recognize the
experimenter's (or expert's) perspective, and then use the
variables generated by the experimenter. High scores on USEDV would
require the subject to use a comparatively larger number of variables in
solving the problem. These findings are consistent with the prevalent
view that adolescent reasoning includes use of multiple variables
(Keating, 1980) and with Linn's (1980) view that the ability to
generate variables for problem solving as well as the ability to use the
experimenter's variables represents a higher level of functioning
and a more mature processing of information. The only outcome variable
that was not significant in the regression analysis was OWNV. Notably,
OWNV did not require a high level of cognitive ability, but rather the
mere use of the subject's own listed variables.
The hypothesis that sexual/contraceptive behaviors and attitudes,
age, and ethnic status would be significant predictors of risk-taking
behavior was only minimally supported. Only one sexual/contraceptive
behaviors variable was found to be a significant predictor. Furthermore,
cognitive capacity was found to be a significant predictor of
contraceptive risk taking.
Sensible use of contraceptives (SENSIB) was predicted by previous
birth control usage. Perusal of answers to the nonscaled items on the
Sexual/Contraceptive Behaviors Questionnaire yielded information of
possible relevance to this finding. In general, contraceptive behavior
was found to be consistent over time. When the subject reported using an
"effective" method, she was very likely to report using the
method consistently. Similarly, when a subject reported using an
"ineffective" method, she was very likely to report using it
inconsistently. Additionally, nonusers of contraceptives were very
consistent in their behavior. The finding that earlier behavior
(previous contraceptive usage) predicts later behavior (SENSIB) is
consistent with results reported by Green (1985), in which earlier
sexual behavior was positively correlated with sexual behavior in late
adolescence, while other factors (e.g., parental influences) were not
found to be correlated. Such a finding emphasizes the importance of
early education regarding contraceptive use.
Pun ability was found to be the best predictor of SENSIB. It is
notable that the variable found to be important in decision making was
also of importance in predicting risk taking in contraceptive use. The
assumption that higher cognitive functioning is related to "better
decision making," which in turn is related to less risk taking, is
one easily made based on face validity. Yet, with the exception of the
Adler et al. (1987) study demonstrating that adolescent behavioral
intention is related to actual use of contraceptives, there is no
precedent in the adolescent contraceptive literature for this finding.
Future research might continue to explore the influence of cognitive
capacity, as well as other potentially influential variables, upon
adolescent contraceptive risk taking.
The authors gratefully acknowledge the assistance of the medical and
nursing staff of the Eastside and Westside Health Clinics of the city
and county of Denver, Colorado.
Sharon A. Johnson, Ph.D., Texas Christian University, Harris College
of Nursing, Fort Worth, Texas.
Reprint requests to Vicki Green, Ph.D., Department of Psychology,
Oklahoma State University, Stillwater, Oklahoma 74078.
REFERENCES
Adler, N. E., Kegeles, S. M., & Irwin, C. E. (1987).
Understanding adolescent contraceptive choice: An empirical test. Paper
presented at the meeting of the American Psychological Association, New
York City.
Brooks-Gunn, J., & Furstenberg, F. F., Jr. (1989). Adolescent
sexual behavior. American Psychologist, 44(2), 249-257.
Byrnes, J. (1988). Formal operations: A systematic reformulation.
Developmental Review, 8, 66-87.
Cobliner, W. G. (1974). Pregnancy in the single adolescent girl: The
role of cognitive functions. Journal of Youth and Adolescence, 3, 17-29.
Cvetkovich, G., Grote, B., Bjorseth, A., & Sarkissian, J. (1975).
On the psychology of adolescents' use of contraceptives. The
Journal of Sex Research, 11, 256-270.
Delamater, J., & MacCorquodale, P. (1979). Premarital sexuality:
Attitudes, relationships, behavior. Madison: University of Wisconsin
Press.
Elkind, D. (1978). Understanding the young adolescent. Adolescence,
8, 127-134.
Elkind, D., & Bowen, R. (1979). Imaginary audience behavior in
children and adolescents. Developmental Psychology, 15, 38-44.
Geis, B. D., & Gerrard, M. (1984). Predicting male and female
contraceptive behavior: A discriminant analysis of groups high, moderate
and low in contraceptive effectiveness. Journal of Personality and
Social Psychology, 46, 669-680.
Gordon, D. E. (1990). Formal operational thinking: The role of
cognitive-developmental processes in adolescent decision-making about
pregnancy and contraception. American Journal of Orthopsychiatry, 60(3),
346-356.
Green, V. A. (1985). Experiential factors in childhood and adolescent
sexual behavior: Family interaction and previous sexual experiences. The
Journal of Sex Research, 21, 157-182.
Green, V., Johnson, S., & Kaplan, D. (1992). Predictors of
adolescent female decision making regarding contraceptive usage.
Adolescence, 27(107), 613-632.
Green, V., Morton, K., Starr, B., Jones, F., & Jaynes, W. E.
(1991). The development of an instrument to measure the personal fable
aspect of adolescent cognitive egocentrism. Manuscript submitted for
publication.
Inhelder, B., & Piaget, J. (1958). The growth of logical
thinking. New York: Basic Books.
Jones, F. A., & Green, V. (1991). Measures of cognitive
development in adolescence. Manuscript submitted for publication.
Kantner, J. F., & Zelnik, M. (1972). Sexual experiences of young
unmarried women in the U.S. Family Planning Perspectives, 4, 9-18.
Keating, D. P. (1980). Thinking processes in adolescence. In J.
Adelson (Ed.), Handbook of adolescent psychology (pp. 211-246). New
York: Wiley.
Levine, D. I., & Linn, M. C. (1977). Scientific reasoning ability
in adolescence: Theoretical viewpoints and educational implications.
Journal of Research in Science Teaching, 14, 371-384.
Linn, M. C. (1980). When do adolescents reason? European Journal of
Scientific Education, 2, 429-440.
Linn, M. C., & Pulos, S. M. (1983). Male-female differences in
predicting displaced volume: Strategy usage, aptitude relationships, and
experience influences. Journal of Educational Psychology, 75, 86-96.
Morrison, D. M. (1985). Adolescent contraceptive behavior: A review.
Psychological Bulletin, 98, 538-568.
Peel, E. A. (1971). The nature of adolescent judgement. New York:
Wiley-Interscience.
Rogel, M. J., Zuehlke, M. E., Peterson, A. C., Tobin-Richards, M.,
& Shelton, M. (1980). Contraceptive behavior in adolescence: A
decision-making perspective. Journal of Youth and Adolescence, 9,
491-506.
Smith, P. B., Nenney, S. W., Weinman, M. L., & Mumford, D. M.
(1982). Factors affecting perception of pregnancy risk in the
adolescent. Journal of Youth and Adolescence, 11, 207-215.
Tomlinson-Keasey, C. (1972). Formal operations in females from eleven
to fifty-four years of age. Developmental Psychology, 6, 364.
Zelnik, M., & Kantner, J. F. (1979). Reasons for nonuse of
contraception by sexually active women aged 15-19. Family Planning
Perspectives, 11, 289-296.
Zelnik, M., & Shah, F. K. (1983). First intercourse among young
Americans. Family Planning Perspectives, 15, 64-70.