Extra Credit As Incentive for Voluntary Research
Laura M. Padilla-Walker Byron. L. Zamboanga
University of Nebraska–Lincoln Smith College
Ross A. Thompson Larissa A. Schmersal
University of California, Davis University of Nebraska–Lincoln
This study examined whether offering extra credit for research par
ticipation was effective at meeting educational goals (e.g., enabling
all students to learn about the research process) and providing a
representative sample of college students for researchers. Results
revealed that less than half (38%) of 193 undergraduate students
in an introductory course participated in research. Those who did
participate scored higher on measures of academic performance
than those who did not participate. Offering extra credit for re
search participation might not meet educational goals and possibly
limits the generalizability of research findings.
University instructors often use extra credit to encourage
student participation and provide additional avenues by
which students can learn course material. Previous studies
have examined instructors’ use of extra credit to increase stu-
dent attendance (Thorne, 2000), motivate students to read
journal articles (Carkenord, 1994), and promote participa-
tion in the classroom (Boniecki & Moore, 2003). Another
option for providing extra credit that has received less empir-
ical attention is allowing students to earn extra credit by par-
ticipating in scientific research as part of a research
participant pool (traditionally called a subject pool).
When researchers first organized participant pools, they
typically targeted large classes of first- and second-year stu
dents who participated as a course requirement. Researchers
have raiseda number of concerns about the coerciveness of re
quiring participation for academic credit (Sieber, 1999; Sieber
& Saks, 1989), prompting an increase in the number of in
structors offering extra credit for research participation. For
example, Landrum and Chastain (1999) reported that almost
25% of a sample of more than 500 undergraduate institutions
offered participation in research as an option for extra credit.
Given the relatively recentpractice of offering participation in
research for extra credit, it has yet to be determined if this op
tion fulfills the educational and research goals of university in
structors and academic departments. This study examined
whether offering extra credit for research participation fulfills
educational goals set forth by instructors and students and re
search goals endorsed by academic departments.
Studies have found that the most commonly used extra
credit options are those that instructors perceive as offering
the greatest educational value to students (e.g., Hill,
Palladino, & Eison, 1993). Those who argue against the use
of extra credit often note that extra credit should be available
for all students, suggesting that instructors are not in favor of
extra credit that benefits only a select few (Norcross, Dooley,
& Stevenson, 1993). Because the educational value of re
search participation (e.g., learning about the research pro
cess) is essential to satisfying the ethical requirements of
student research participation (Sieber, 1999), a number of
studies have examined the potential educational benefits of
participating in research, and the results have been mixed.
For example, after measuring research experiences at several
universities, Miller (1981) stated that there was little evi-
dence of pedagogic value in research participation. Alterna-
tively, others have found that participation in research helps
students to better understand psychology (Landrum &
Chastain, 1995). There has been much less empirical atten-
tion to the argument proposed by critics of extra credit: The
majority of students do not participate in extra credit oppor-
tunities. Thus, our study examined whether students en-
rolled in a large introductory psychology course would take
advantage of the opportunity to voluntarily participate in re
search for extra credit.
It is commonpractice forinstructors and departmentsto of
cessible college student population to researchers using
participant pools. Beyond fulfillingan educationalresponsibil
ity to student participants, a research participant pool must
tative of the broaderundergraduate population. Itremains un
clear how offering participation in research for extra credit
affects the generalizability of research conducted using re
search participant pool samples. Critics attest that using any
university sample may limit the generalizabilty of research
findings to the broader population (Sears, 1986). Thus, it is
possible that offering voluntary research for extra credit exac
erbates existing differences between university samples and
the broader population. Indeed, research suggests that there
are demographic and psychological differences between indi
viduals who voluntarily participate in an activity and those
whodo not (Rosenthal & Rosnow,1975).Therefore,ourstudy
150 Teaching of Psychology
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also examined whether students who voluntarily participated
in research for extra credit differed in academic achievement
and motivation from those who chose not to participate.
In summary, this study had two goals that we examined us
ing instructor records from a large introductory psychology
course. First, we sought to determine whether the majority of
students would participate in research when given the option
as extra credit. Second, we examined whether there were dif
ferences on measures of academic achievement between stu
dents who participated in research for extra credit and
students who did not.
Participants were 193 college students enrolled in an in
troductory psychology course at a Midwestern state univer
sity (34% men; 70% first-year students). This course was a
fairly conventional large-enrollment introductory course.
Students met twice a week for lecture (75 min) in a large au
ditorium and once a week in a small-enrollment seminar sec
tion (50 min) led by a graduate teaching assistant. The
lecture section encompassed the presentation of new infor
mation through the use of visual software, discussions, and
videos. The seminar section focused on demonstrations, in-
formal experiments, discussions, and preparation for exams.
The total number of students with complete data was 152.
Analyses excluding those with missing data did not differ
from analyses including those with missing data, so for com-
pleteness the analyses included the entire sample. We did not
ask participants questions regarding student ethnicity, but
most students were state residents and thus reflected the
state’s predominantly White middle-income population.
We used instructor records (i.e., records of seminar and
lecture attendance, homework scores, paper scores, and
exam scores) for this study. Prior to taking the final (i.e.,
fourth) exam, students completed a brief paper-and-pencil
questionnaire that assessed student motivation and other
course-specific information. Because we gathered research
materials as part of our effort to improve students’ academic
performance (i.e., our primary goals related to educational
practice) and relied primarily on educational records, we did
not obtain informed consent, but the instructor told students
they could decline to complete any self-report measures with
out penalty. Because we obtained the outcome measure (i.e.,
research participation) through the end of the semester, we
did not provide a formal debriefing. The institutional review
board at the university where we conducted this study ap
proved these procedures as described.
Extra credit. The instructor gave students the opportu
nity to receive extra credit points through research participa
tion or involvement in an experiential activity (e.g., attending
a conference or talk related to psychology). To encourage stu
dent research participation, the instructor reminded students
throughout the semester (after each unit exam and before the
final) that the opportunity to participate in research was
available. Periodically, research assistants announced oppor
tunities to participate in a study and profiled their research
projects shortly before lecture ended. Each research credit
hour was worth 2 points, which the instructor added to stu
dents’ course grade. Students could receive a maximum of 10
points of total extra credit (5 hr of research participation).
The instructor required those who elected the experiential
option to submit a short reflection and integration paper of
the activity (2 points for the activity; 1 point for paper). Only
11 out of 193 (6%) students chose to do the alternative expe
Student background. Student background measures in
cluded self-reported ACT scores and first-semester college
grade point average (GPA).
Exam performance. We computed exam scores as the
average of students’ scores on four 50-point (noncumulative)
multiple-choice exams. The alpha coefficients for Exams I
through IV were .80, .87, .83, and .85, respectively, with a
mean alpha coefficient of .84 across all four exams.
Paper performance. We computed paper scores as the
average of students’ scores on two 25-point papers. Paper
scores were significantly correlated with each other, r(192) =
.48, p < .01.
Seminar performance. We computed seminar perfor-
mance scores by summing the number of seminar classes at-
tended, the seminar homework scores, and scores on the sem-
inar exam for each student.
Lecture attendance. The instructor assessed lecture at
tendance at 13 random points during the semester. We com
puted lecture attendance by summing the students’ lecture
attendance derived from these periodic assessments.
Overall course performance. We computed overall
course performance by summing each student’s exam scores,
paper scores, seminar performance, and lecture attendance.
When computing overall course performance, we did not in
clude extra credit points and did not weight the scores.
Academic motivation. We measured academic motiva
tion using four questions to assess students’ attitudes about
class performance (α = .70). Students rated on a 4-point
scale, ranging from 1 (does not describe me at all)to4(describes
me extremely well), how motivated they were to attend class
and pay attention in lecture, read and keep up with daily as
signments, achieve a grade of B or better, and put in just
enough effort in class so they could pass (a grade of C). We re
versed students’ response ratings on the last question and av
eraged all four scores to create an overall academic motiva
Vol. 32, No. 3, 2005 151
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Thisstudy examined the percentage ofstudents who partic
ipated in research and the academic characteristics of those
who participated. In addition, we examined whether students
who voluntarily participated in research for extra credit dif
fered on demographic characteristics, academic performance,
and academic motivation from those who did not voluntarily
participate. Prior to analysis, we examined variables for
univariate outliers. We deleted four cases with extremely low
scoreson overall course grade, leaving189casesforanalysis.
We conducted a number of univariate ANOVAs to deter
mine if there were differences in the frequency of participa
tion in research as a function of year in school or gender.
Although no significant differences emerged as a function of
year in school, results showed that women (M = 3.94, SD =
1.75) voluntarily participated in more research studies than
men (M = 2.91, SD = 1.86), F(1, 66) = 5.23, p < .05, partial
= .06. Partial η
values are an estimate of the proportion of
variance in the dependent variable associated with the inde
pendent variable (Tabachnick & Fidell, 2001). An effect size
of .06 is considered low (Cohen & Cohen, 1975), which sug
gests that the difference between participation rates of
women and men may not be meaningful.
Research Participation and General Academic
We conducted a number of chi-square analyses to deter-
mine if those who participated in research differed in gender
or year in school from those who did not participate. Results
showed no statistically significant group differences. We also
conducted a number of chi-square analyses to determine if
there were differences in participation as a function of aca
demic performance. We categorized performance by assess
ing overall course grades, with performance earning a letter
grade of A categorized as excellent, performance earning a B
categorized as good, performance earning a C categorized as
average, and performance earning below a C categorized as
below average. Performance scores did not include extra
credit points. Chi-square analyses revealed that when given
the option to participate in research, significantly more stu
dents who earned below average, χ
(1, N = 34) = 27.15, p <
.001, and average, χ
(1, N = 59) = 6.12, p < .01, letter
grades elected not to participate. There were no statistically
significant differences in the number of students choosing
whether to participate among good and average groups. In
addition, the proportion of students participating from each
category differed, with 63% of students earning excellent
grades, 43% of students earning good grades, 34% of students
earning average grades, and 5% of students earning below av
erage grades volunteering to participate in research. Further
more, of the 72 students (38% of sample) who participated in
research, 3% earned below average grades, 28% earned aver
age grades, 32% earned good grades, and 38% earned excel
Differences in Academic Performance and Motivation
We conducted a number of univariate ANOVAs to deter
mine if there were differences in academic performance and
motivation between students who participated in research
and those who did not. Significant mean differences in exam
performance, paper performance, seminar performance, lec
ture attendance, overall course performance, and motivation
emerged between the two groups, with those who partici
pated in research having higher scores compared to those
who did not participate (see Table 1). Group differences on
ACT scores and GPA were not statistically significant.
This study examined the use of extra credit as a voluntary
option for research participation and the effectiveness of this
procedure in meetingeducational goals set forth byinstructors
and students as well as departmental and professional goals of
providing a representative sample of college-aged students for
researchers. Overall, the findings suggest that the educational
goal of encouraging all students to profit from the educational
benefits of scientific research was not met in this study, with
less than half of students (38%) opting to participate in re
search for extra credit. Of those who did participate, the ma
jority (70%) were students who earned excellent or good
grades, with considerably fewer students (3%) who earned be-
low average grades electing to participate. Furthermore, those
who volunteered for research participant pools differed on ac-
ademic performance variables and academic motivation from
those who did not voluntarily participate.
The primary goal of this study was to better understand the
educational value of using research participation as an option
for extra credit. It is likely that one purpose of this practice for
instructors is to provide educational opportunities for stu-
dents, whereas students might also value the chance to raise
their course grades (Bender,1986). Instructorsmight alsopre-
ferthatthemajority of students take advantage of theopportu
nity to learn about scientific research (Norcross et al., 1993).
Although good students commonly obtained extra credit
(some of whom might want to raise their grade from a B to an
A), the greatest percentage of students who participated in re
search for extra credit were those who already had an A in the
class. It is possible that these individuals participated in re
search merely as a means to secure a high grade in the class or
for the educational benefit and opportunity of participation.
Either way, it is clear that the majority of students did not take
advantage of this educational opportunity, which raises ques
tions regarding the educational utility of such practices. In
deed, students who wouldseemingly benefitthe mostfrom this
opportunity (i.e., students with below average grades) were
the least likely to voluntarily participate.
The secondary goal of this study was to determine if the
departmental goal of providing a participant pool that is rep
resentative of the university population was affected by offer
ing research participation as an option for extra credit.
Differences emerged in all measures of class performance and
academic motivation, which suggests that students who were
motivated to do well in class were also motivated to complete
extra credit by participating in research. This finding builds
152 Teaching of Psychology
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on prior research documenting differences in background
variables (e.g., personality differences; Rosenthal & Rosnow,
1975) between those who volunteer and those who do not.
These differences have potential implications for the
generalizability of research studies conducted using research
participant pools, especially research that explores academic
achievement characteristics of college student populations.
Taken together, these findings invite further exploration
into the practice of offering extra credit for participation in
research to determine whether students perceive the experi-
ence as educational or merely as a way to secure higher
course grades. In addition, if research does have educational
value, these findings suggest that a large proportion of stu-
dents at large universities are not taking advantage of this ed-
ucational opportunity when it is offered as extra credit, which
might suggest value in requiring participation in research in
an effort for students to more clearly understand the scien-
tific process inherent in psychology. Requiring research par-
ticipation would necessitate that departments assume the
responsibility of enhancing the educational benefits of re
search participation through creative and interesting debrief
ing procedures and follow-up evaluations to systematically
assess whether students are obtaining educational benefits
from participating in research (Sieber, 1999).
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1. We thank Eric Owens and Sherill Pineda for their assistance with
2. Send correspondence to Laura M. Padilla-Walker, Department of
Marriage, Family, and Human Developmnet, Brigham Young Univer
sity, 2097 JFSB, Provo, UT 84602; e-mail: email@example.com.
Vol. 32, No. 3, 2005 153
Table 1. Mean Academic Performance and Motivation Scores for Research Participants
Voluntary Research Participation
Did Not Participate
M SD M SD F
ACT score 24.49 3.53 24.63 3.78
(1, 127) = 0.04
College GPA 3.11 0.63 3.07 0.53
(1, 139) = 0.17
Exam performance 37.43 4.90 34.38 6.05
(1, 181) = 12.90**
Paper performance 43.09 5.01 35.54 13.08
(1, 187) = 20.15**
Seminar performance 94.93 14.75 82.60 19.60
(1, 182) = 20.89**
Lecture attendance 11.50 1.97 9.92 2.45
(1, 189) = 26.80**
Overall course performance 299.26 31.33 267.95 42.97
(1, 182) = 28.47**
Motivation 12.25 2.41 11.39 2.68
(1, 150) = 4.21*
GPA = grade point average.
< .05. **
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