Creative Education
2012. Vol.3, Supplement, 77-81
Published Online December 2012 in SciRes (http://www.SciRP.org/journal/ce) DOI:10.4236/ce.2012.38b017
Copyright © 2012 SciRes. 77
Enhancing Pre-service Teacher’s Self-efficacy and Technological
Pedagogical Content Knowledge in Designing Digital Media
with Self-Regulated Learning Instructional Support in Online
Project-Based Learning
Pornsook Tantrarungroj, Praweenya Suwannatthachote
Faculty of Education, Chulalongkorn University, Bangkok, Thailand
Email: pornsook.t@chula.ac.th
Received 2012
This study investigated pre-service teachers’ self-efficacy in designing digital media and their techno-
logical pedagogical content knowledge (TPCK) for designing digital media using different forms of self-
regulated learning instructional support for online project-based learning. The study used a 2 × 2 factorial
research design. The sample consisted of 232 pre-service teachers from an institution situated in Bangkok,
Thailand. The four different forms of self-regulated learning instructional support for online project-based
learning were PB + SQ + PA, PB + SQonly, PB + PAonly, and PBonly. Two-way Multivariate Analysis
of Variance (MANOVA) was used for data analysis. The results showed significant differences in
pre-service teachers’ self-efficacy and TPCK posttest scores. No main effect was found between two dif-
ferent self-regulated learning strategies (SQ and PA) upon the means of self-efficacy in designing digital
media scores and TPCK scores. The self-regulated learning strategies (SQ and PA) had a statistically sig-
nificant interaction upon the means of self-efficacy in designing digital media scores while the self-regu-
lated learning strategies (SQ and PA) had no interaction upon the means of the TPCK scores.
Keywords: Online Project-Based Learning; Peer Assessment; Pre-Service Teacher; Self-Efficacy;
Technological Pedagogical Content Knowledge (TPCK)
Introduction
Teacher education is designed to equip pre-service teachers
with the pedagogical content knowledge, skills, and attitude
that are required for classroom teaching. In general, teachers
possess teaching expertise that is derived from a combination of
pedagogical knowledge, content knowledge, knowledge of
students, and knowledge of environmental context (Koehler &
Mishra, 2008; Shulman, 1986). With the growing use of tech-
nology in the educational environment, information and com-
munication technology (ICT) has become a powerful tool for
extending educational opportunities. The training of teachers in
the educational uses of technology appears to be a key compo-
nent in every improvement plan for education (Angeli &
Valanides, 2009; Magliaro & Ezeife, 2007). Teachers need to
combine technological knowledge, pedagogical knowledge, and
content knowledge, when using ICT in classroom. The term
“technological pedagogical content knowledge (TPCK)” is used
to represent teachers’ expertise in technology integration. This
is a form of knowledge that is required for the intelligent use of
technology in teaching and learning (Angeli & Valanides, 2009;
Chai, Koh, Tsai, & Tan, 2011; Koehler & Mishra, 2008). Re-
searchers presuppose that effective technology integration
should be formulated by considering the interactions among
technology, content, and pedagogy. Thus, pre-service teachers
should be grounded not only in the knowledge of content and
pedagogy, but also in the knowledge of technology before be-
ginning their teaching field experiences.
Teachers require technological knowledge and technological
skills before attempting to utilize technology in class. Accord-
ing to Magliaro and Ezeife (2007), most new teachers have
limited knowledge of how to integrate information technology
into their professional practice and curriculum even though pre-
service teachers have formal training in instructional technol-
ogy. The frequency of teaching with computers is related to
teachers’ self-efficacy beliefs (Albion, 1999). Self-efficacy
means the beliefs a person has about their capability to effec-
tively perform a particular behavior or task (Cassidy & Eachus,
2002). Bandura’s social cognitive theory was used to formulate
a theoretical view for studying the computer self-efficacy of
pre-service teachers. Four major activities determine the at-
tainment of different levels of self-efficacy: (1) performance
accomplishments, (2) vicarious experiences, (3) verbal persua-
sion, and (4) emotional arousal (Bandura, 1986; Magliaro &
Ezeife, 2007). According to Wall (2004), pre-service teachers
with lower computer self-efficacy are more likely to have
problems with technology integration and are likely to have
problems integrating technology into their own classroom when
they finish their teacher education program. Therefore, an in-
creased amount of positive exposure to technology in all areas
of academia may generate more favorable attitudes toward
computers and educational technology.
Self-regulation is a self-directive processes while self-beliefs
are viewed as proactive processes that can be developed and
increased during students’ self-regulated learning (Fitzpatrick,
1999; Zimmerman, 1989). A person can become a more
P. TANTRARUNGROJ, P. SUWANNATTHACHOTE
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78
self-regulated learner by acquiring different strategies. Accord-
ing to Zimmerman (1989), self-regulated learning involves the
regulation of three general aspects of academic learning,
namely, behavior, motivation, and cognition. A combination of
these three aspects appears to help people achieve their learning
goals. The self-regulated learning strategies include but are not
limited to goal setting, time management, help seeking,
self-questioning, and peer assessment. Pre-service teachers are
expected to be knowledgeable about current technology and to
know how it can be used to promote learning. They are also
expected to be able to utilize and integrate the technology
available into the classroom effectively. Thus, pre-service
teachers’ strengths and weaknesses as they attempt technology
integration should be evaluated in order to determine their po-
tential for the effective use of ICT in the classroom. The current
literature on computer self-efficacy lacks a combination of
designing digital media and self-regulated learning. This study
was intended to investigate pre-service teachers’ self-efficacy
in designing digital media, and their TPCK in designing digital
media using different forms of self-regulated learning instruc-
tional support for online project-based learning.
Online project-based learning is a dynamic approach in
which pre-service teachers explore real-world situations and
challenges. With this type of active and engaged learning,
pre-service teachers are stimulated to obtain a deeper knowl-
edge of the content. Active involvement in learning is posi-
tively related to learning outcomes (Ge & Land, 2008;
Kramarski & Michalsky, 2010). Designing digital media re-
quires the designers or teachers to integrate content knowledge,
pedagogical knowledge, and technological knowledge that
appropriate for the learners’ characteristics such as grade level,
background knowledge, and level of content.
The self-questioning that was developed based on metacog-
nitive self-questioning (Kramarski & Michalsky, 2010). It was
divided into four categories 1) comprehension questions e.g.
“what are learning tasks in digital media?”, 2) connection ques-
tions e.g. “how do you select a teaching method to deliver con-
tent?”, 3) strategy questions e.g. “what is your teaching strategy
when designing content for this digital media?”, and 4) reflec-
tive questions e.g. “why and how do you choose instructional
strategies for your digital media in order to support learning?”.
Tseng and Tsai (2007) found that peer assessment feedback
in the form of reinforcement feedback had positive correlation
with quality of product improvement. Peer assessment supports
team cooperative learning (Fitzpatric, 1999). In the present
study, pre-service teachers were required to assess group mem-
bers’ digital media storyboard design using four criteria 1) con-
tent, 2) design, 3) attractiveness, and 4) clarification. This re-
search also investigated students’ perspective on different for-
mats of self-regulated learning instructional support for online
project-based learning. The three instructional support strate-
gies used were: 1) self- questioning and peer assessment (SQ +
PA), 2) self-questioning (SQonly), and 3) peer assessment
(PAonly).
This study attempted to help pre-service teachers gain higher
self-efficacy and TPCK for designing digital media through
online project-based learning; and to help them to be confident
in their ability to integrate technology in the classroom. It was
also designed to help educators understand the benefits of pro-
viding different formats for self-regulated learning instructional
support for online project-based learning in the teacher educa-
tion program.
Research Questions
The purpose of this study was to investigate the effectiveness
of self-regulated learning instructional support for online pro-
ject-based learning on students’ self-efficacy in designing digi-
tal media. The research questions used were as follows:
Q1: Are there significant differences in the posttest of self-
efficacy when designing digital media between pre-service
teachers who received different forms of self-regulated learning
instructional support?
Q2: Are there significant differences in the posttest of TPCK
when designing digital media between pre-service teachers who
received different forms of self-regulated learning instructional
support?
Q3: What main effect and interaction are found between two
different self-regulated learning strategies upon the means of
self-efficacy and TPCK when designing digital media scores?
Research Method
The purposes of this study were 1) to compare the means of
self-efficacy and TPCK for designing digital media scores be-
tween pre-service teachers who received different forms of self-
regulated learning instructional support for online project-
based learning, 2) to study the main effect and interaction be-
tween two different self-regulated learning strategies (SQ and
PA) upon the means of self-efficacy in designing digital media
scores and TPCK scores, and 3) to investigate the behavior of
pre-service teachers when collaborating in online-based learn-
ing. The study used a 2 × 2 factorial research design.
The independent variables, self-questioning and peer as-
sessment strategies, were the two forms of self-regulated learn-
ing instructional support for online project-based learning. The
dependent variables were pre-service teachers’ performance in
both self-efficacy for designing digital media and TPCK.
Research Participants
The participants were pre-service teachers from an institution
situated in the center Bangkok, Thailand who enrolled in the
pre-service teacher undergraduate course 2726207 ED TECH
INFO at Chulalongkorn University during the 2011 academic
year. Two hundred and forty-two students agreed to participate
in this study; however, 232 were eligible.
The demographics data for the participant shows that 31.5%
were males, and 68.5% were females. They came from different
majors such as science, social science, arts, and music. Partici-
pants were randomly assigned to groups on the basis of their
majors and TPCK pretest scores in the way that ensured that
students with different majors and high, average, and low
TPCK ability were included in each group. During the six
weeks, pre-service teachers were assigned to work in small
groups of 4-5 students.
The four different instructional strategies were:
Online project-based learning supported by self-questioning
and peer assessment (PB + SQ + PA).
Online project-based learning supported by self-questioning
only (PB + SQonly)
Online project-based learning supported by peer assessment
only (PB + PAonly)
Online project-based learning only (PBonly)
Instrumentation
The five research instruments used were: 1) a 7-week lesson
P. TANTRARUNGROJ, P. SUWANNATTHACHOTE
Copyright © 2012 SciRes. 79
plan, 2) pre/post tests for TPCK in designing digital media, 3)
pre/post self-efficacy in designing a digital media survey, 4)
self-evaluation questions, and 5) storyboard design rubrics.
1) The 7-week lesson plan was based on the six major steps
of the project-based learning approach. Pre-service teachers
were randomly assigned to work in small groups of 4-5. Each
person was responsible for individual and group work. Online
activities took place in the Blackboard Learning Management
System. Pre-service teachers completed the self-efficacy in
designing digital media survey and the TPCK test during the
first week. During the six weeks of the experiment, pre-service
teachers were required to use the online communication tools
provided for individual work and group work project assign-
ments. Each participant was required to introduce themselves,
present and discuss learning resources, design a storyboard for
the digital learning object, undertake collaborative work for the
group project, and submit their projects. In the last week, pre-
service teachers worked individually and in groups to evaluate
storyboards and to provide feedback to other groups.(Table 1)
2) The pre/post tests for the TPCK in designing digital media
were based on ICT-TPCK criteria (Angeli & Valanides, 2009;
Chai, Koh, Tsai, & Tan, 2011). This test was designed to measure
participants’ knowledge in four areas: 1) identification of the
technique and the teaching methods for the infusion of tech-
nology into the design of the digital learning object, 2) identifi-
cation of technology for transforming the content to be taught
into forms that were comprehensible to learners, 3) identifica-
tion of appropriate pedagogical uses which are difficult or im-
possible to be implement by traditional means, and 4) selection
of appropriate ICT tools and teaching techniques.
3) The pre/post self-efficacy in designing the digital media
survey was based on self-efficacy in computer and technologi-
cal skills (Lee & Tsai, 2010; Murphy, Coover, & Owen, 1989;
Usher & Pajares, 2008). The survey was provided through
Google Docs, which was used to gather the pre/post self-effi-
cacy for designing digital media data. A five point Likert-type
scale, from lowest 1) to highest 5) was used. It was composed
of two sections (a) demographic information and (b) self-effi-
cacy for TPCK knowledge integration for designing digital
media. The 30 statements in the second section of the survey
were designed to evaluate four areas of the respondents’
self-efficacy: 1) mastery experience, 2) vicarious experience
from peers, 3) social persuasion, and 4) physiological state.
4) The self-evaluation questions were based on metacogni-
tive self-questioning (Kramarski & Michalsky, 2010). The self-
evaluation questions were designed to facilitate respondents’
comprehension, to create connections between tasks and com-
prehension, to stimulate the use of an appropriate strategy for
designing digital media, and to reflect on and evaluate their
design performance. Pre-service teachers were asked to evalu-
ate themselves during their online group projects.
Table 1.
Group Assignment.
TPCK pretest scores
Instructional
Strategies High Average Low
PB+SQ+PA
PB+PAonly
PB+SQonly
PBonly
14
14
13
14
30
29
29
30
15
14
15
15
Total 118 59 232
5) The storyboard design rubric was used to evaluate indi-
vidual and group projects according to four criteria: content,
design, attractiveness, and clarification. Each category had
three different levels of performance.
Research Procedure (Figure 1)
Each participant completed the pretest TPCK and self-effi-
cacy in designing digital media survey at the beginning of the
study. Pre-service teachers were randomly assigned to groups
on the basis of the following research groups: PB + SQ + PA,
PB + PAonly, PB + SQonly, and PBonly. The participants
worked collaboratively on online project-based learning under
four instructional strategies, with each participant designing a
storyboard for the digital learning object.
Online Project-based Learning. Project-based learning is a
teaching method that engages students in learning essential
knowledge and life-enhancing skills and through an extended,
students are involved in an inquiry process around complex
questions and carefully designed products and tasks (An & Kim,
2007). Online Project-based Learning was designed according
to the six major steps of the project-based learning approach
including 1) discussion of the project topic and needs, 2) in-
quiry and accumulation for necessary information, 3) definition
and selection of guidelines for project development, 4) planning
and accumulation of the necessary materials, 5) creation of the
storyboard, and 6) reflection on and evaluation of group work.
Upon completing the online project-based learning, the pre-
service teachers would be able to
1) synthesize, analyze, and derive appropriate topics and
content for designing digital media
2) integrate teaching methods and media components for
learning object information
3) design the flow and storyboard according to digital media
design principles
4) evaluate the appropriateness of different learning object
design principles
Figure 1.
Research Procedure.
P. TANTRARUNGROJ, P. SUWANNATTHACHOTE
Copyright © 2012 SciRes.
80
Tools for Blackboard Group Properties. The Blackboard LMS
was used as a learning place for the participants. The following
communication tools were provided: Collaboration, File Ex-
change, Group Discussion Board, and Emails. Figure 2 pre-
sents a sample of a screen used during the process. Six steps of
the online project-based learning were carried on using the
Blackboard Group properties. Pre-service teachers were re-
quired to logon and have a discussion with their peers at least
3-4 times per week. The results showed that pre-service teach-
ers used various tools to communicate among group members
such as e-mails, Facebook, and personal mobile phones. Most
of students (91.81 %) had a high level of participation behavior
for collaborating in an online group project.
Results
The statistical results showed that pre-service teachers who
experienced online project-based learning with different types
of self-regulated learning strategies had significantly higher
posttest scores for self-efficacy in designing digital media
compared to their pretest scores at the .05 level. Table 2 shows
the mean scores, standard deviations, and pre and post scores
for self-efficacy in designing digital media.
The results demonstrate that pre-service teachers who ex-
perienced online project-based learning with different types of
self-regulated learning strategies had significantly higher post-
test scores statistically for TPCK in designing digital media
than pretest scores at the .05 level. Table 3 shows the mean
scores, standard deviations, and pre and post scores for TPCK.
There was no main effect between the two different self-
regulated learning strategies (SQ and PA) upon the means of
self-efficacy in designing digital media scores and TPCK scores;
Figure 2.
A screen capture of the online group tools.
Table 2.
Self-efficacy in Designing Digital Media Scores.
Self-efficacy in designing
digital media scores N M S.D. t. p
PB+SQ+PA
Pre
Post
59
3.38
3.85
.51
3.85
7.22
.000*
PB+SQonly
Pre
Post
57
3.32
3.64
.59
3.64
5.18
.000*
PB+PAonly
Pre
Post
57
3.39
3.66
.54
3.66
3.79
.000*
PB only
Pre
Post
59
3.45
3.71
.59
3.72
3.85
.000*
Total 232
*p < .05.
the self-regulated learning strategies (SQ and PA) had no main
effect upon the means of self-efficacy in designing digital me-
dia scores and TPCK scores; the self-regulated learning strate-
gies (SQ and PA) had statistically interaction upon the means
of self-efficacy in designing digital media scores at the .05 level;
and the self-regulated learning strategies (SQ and PA) had no
interaction upon the means TPCK scores. Table 4 shows the
result of two-way Multivariate Analysis of Variance (MANOVA)
of SQ and PA affecting self-efficacy and TPCK.
Discussion
The results show that pre-service teachers who experienced
online project-based learning with different types of self-regu-
lated learning strategies had a statistically significantly higher
score in the posttest for self-efficacy in designing digital media
and TPCK than in their pretest scores at the .05 level. This re-
sult indicated that TPCK is a unique body of knowledge (An-
geli & Valanides, 2009) which is the result of the combination
and interaction of its contributing knowledge bases. Those three
main knowledge will be effective when the teacher training
program provides and applies it all as integration knowledge for
learners. In this study students became active learners during
online project-based learning, they planned, searched, defined,
Table 3.
TPCK in Designing Digital Media Scores.
TPCK in designing
digital media scoresN M S.D. t. p
PB+SQ+PA
Pre
Post
59
9.27
10.75
2.79
2.33
4.47
.000*
PB+SQonly
Pre
Post
57
9.26
10.51
2.56
2.12
3.15
.003*
PB+PAonly
Pre
Post
57
9.25
10.56
2.73
2.49
3.28
.002*
PB only
Pre
Post
59
9.02
10.07
2.46
2.48
2.72
.002*
Total 232
*p < .05.
Table 4.
Two way Multivariate Analysis of Variance SQ & PA Affecting Self-
efficacy and TPCK.
SourcesVariables SS df MS F p
Self-efficacy .18 1 .18 .78 .38
SQ (A) TPCK 5.67 1 5.67 1.02.31
Self-efficacy .34 1 .34 1.44.23
PA (B) TPCK 7.73 1 7.74 1.39.24
Self-efficacy1.06 1 1.06 4.53.03 *
(AXB) TPCK .96 1 .95 .17 .68
Self-efficacy53.28 228 .23
error TPCK 1271.19 228 5.57
Self-efficacy3264.75 232
Total TPCK 26717.00 232
*p < .05.
P. TANTRARUNGROJ, P. SUWANNATTHACHOTE
Copyright © 2012 SciRes. 81
and refined their understanding. During the six-week experi-
ment, pre-service teachers were involved in various activities.
The individual assignment required each individual to design a
digital media storyboard. This initial assignment promoted
pre-service teachers’ self-efficacy; later they worked in groups
to share ideas and resources. In the students’ inquiry process,
they needed to search for information, to distinguish related and
non-related teaching materials, and to select technological tools
for digital media. Through group discussion, they were able to
integrate appropriate teaching methods and media components
in their storyboard according to digital media designing princi-
ples. They also were exposed to examples of good and poor
design in digital media through an evaluation activity. These
activities along with the self-regulated learning instructional
support for the online project-based learning helped the pre-
service teachers to understand and develop their TPCK compe-
tency. It also promoted the pre-service teachers’ self-efficacy in
designing digital media. By experiencing more information
technology-related pedagogy, teachers developed higher levels
of ICT self-efficacy (Lee & Tsai, 2010).
This study found that there was no main effect between two
different self-regulated learning strategies (SQ and PA) upon
the means for self-efficacy in designing digital media and those
for TPCK scores while the self-regulated learning strategies
(SQ and PA) had no main effect upon the means for self-effi-
cacy in designing digital media scores and TPCK scores. How-
ever, the results showed that (1) the students who received peer
assessment strategies (PB + SQ + PA and PB + PAonly) had
higher self-efficacy mean scores in designing digital media than
those with no-peer-assessment strategies (PB + SQonly and
PBonly) and (2) the students who received self-questioning
strategies (PB + SQ + PA and PB + SQonly) had higher TPCK
mean scores than those with the non-self-question strategies
(PB + PAonly and PBonly). The self-regulated learning strate-
gies (SQ and PA) had statistically interaction upon the means
of self-efficacy in designing digital media scores at the .05 level.
The results were consistent with prior research (Emmer &
Hickman, 1991), indicating that self-efficacy had interaction
upon decision, behavior, and performance of teachers. Conse-
quently, teachers should provide two self-regulated learning
strategies (SQ and PA) to students who have no previous ex-
perience in designing digital media. Once students are able to
accomplish a task, they will have stronger self-efficacy beliefs.
Information and communication technology integration in
the classroom requires further attention in the teacher training
program. For pre-service teachers who have less teaching ex-
perience, different formats of self-regulated learning instruc-
tional support for online project-based learning is recom-
mended to enhance their self-efficacy and TPCK competency.
REFERENCES
Albion, P. R. (1999). Self-efficacy Beliefs as an Indicator of Teachers’
Preparedness for Teaching with Technology. Retrieved February 29,
2012, from
http://www.usq.edu.au/users /albion /papers/site99/1345.html
An, H., & Kim, S. (2007). The perceived benefits and difficulties of
online group work in a teacher education program. International
Journal of Instructional Technology and Distance Learning, 4, 3-19.
Retrieved December 15, 2011, from
http://www.itdl.org/Journal/May_07/article01.htm
Angeli, C., & Valanides, N. (2009). Epistemological and methodologi-
cal issues for the conceptualization, development, and assessment of
ICT-TPCK: Advances in technological pedagogical content knowl-
edge (TPCK). Computers & Education, 52, 154-168.
Bandura, A. (1986). Social foundations of thought and action: A social
cognitive theory. Englewood Cliffs, NJ: Prentice-Hall.
Cassidy, S., & Eachus, P. (2002). Developing the computer user
self-efficacy (CUSE) scale: Investigating the relationship between
computer self-efficacy, gender and experience with computers.
Journal of Educational Co m p uting Research, 26, 133-153.
Chai, C. S., Koh, J. H. L., Tsai, C., & Tan, L. L. W. (2011). Modeling
primary school pre-service teachers’ technological pedagogical con-
tent knowledge (TPACK) for meaningful learning with information
communication technology (ICT). Computers & Education, 57,
1184-1193.
Emmer, E. & Hickman, J. (1991). Teacher efficacy in classroom man-
agement. Education a l and Psychological Measurement, 51, 755-765.
Fitzpatrick, C. (1999). Students as evaluators in practicum: Examining
peer/self-assessment and self-efficacy. Paper presented at the Na-
tional Conference of the Association for Counselor Education and
Supervision, New Orleans, LA.
Ge, X., & Land, S. M. (2003). Scaffolding students’ problem-solving
processes in an ill-structured task using question prompts and peer
interactions. Educational Technology Research and Development, 51,
21-38.
Koehler, M. J., & Mishra, P. (2008). Introducing TPCK. In Silverman,
N. (Ed.), Handbook of technological pedagogical content knowledge
(TPCK) for educators (pp. 1-20). New York: Routledge.
Kramarski, B., & Michalsky, T. (2010). Preparing preservice teachers
for self-regulated learning in the context of technological pedagogi-
cal content knowledge. Learning and Instruction. 20, 434-447.
Lee, M. H., & Tsai, C. C. (2010). Exploring teachers’ perceived self
efficacy and technological pedagogical content knowledge with re-
spect to educational use of the World Wide Web. Instructional Sci-
ence, 38, 1-21.
Magliaro, J., & Ezeife, A. N. (2007). Preservice teachers’ preparedness
to integrate computer technology into the curriculum. Canadian
Journal of Learning and Technology, 33, 95-111. Retrieved Decem-
ber 15, 2011, from
http://www.cjlt.ca/index.php /cjlt/article/view/163/153
Murphy, C. A., Coover, D., & Owen, S.V. (1989). Development and
validation of the computer self-efficacy scale. Educational and Psy-
chological Measurement, 49,893-899.
Shulman, L. S. (1986). Those who understand: Knowledge growth in
teaching. Educ a t io n a l Researcher, 15, 4-14.
Tseng, S. C., & Tsai, C. C. (2007). On-line peer assessment and the role
of the peer feedback: A study of high school computer course. Com-
puters & Education, 49, 1161-1174.
Usher, E. L., & Pajares, F. (2008). Sources of self-efficacy in school:
critical review of the literature and future directions. Review of Edu-
cational Research, 78 , 751-796.
Wall, A. (2004). An evaluation of the computer self-efficacy of preser-
vice teachers. Unpublished doctoral dissertation. Tennessee State
University, Nashville.
Zimmerman, B. J. (1989). A social cognitive view of self-regulated
academic learning. Journal of Educational P s y c ho l o gy , 81, 329-339.