The Effect of Problem-Based Learning on Long-term Content Retention

Kathy Gabric and Tom Ludovice

Hinsdale Central High School

5500 S. Grant Street

Hinsdale, IL  60521

Abstract

Long-term effects on content retention, measured three years after the presentation of materials, indicate a significant improvement in content retention for those students who learned through Problem Based Learning (PBL) relative to those who learned more traditionally.  Students that participated in PBL thought that the project expanded their research skills.  The realistic approach gave most students greater satisfaction in the learning process than traditional methods while level of involvement with parents and peers increased their learning connections.  In addition, the vast majority of students said PBL helped them form opinions about serious issues that they may meet in the future.

Background and Purpose

Problem Based Learning (PBL) units have been implemented in some of our science classes for the past eight years.  Anecdotal evidence indicated a positive experience for many students, especially for students who do not favor traditional teaching methods.  The PBL unit studied in this report covers the content areas of both human reproduction and the structure and function of the brain.  Groups of three to four students are put into the role of doctors who must diagnose a medical problem based on the patient's medical file.  The nature of the prognosis will cause students to grapple with a variety of medical, ethical, and technological issues.  They research all possible treatment options for their diagnosis.  Progress in student research is measured through both personal journals and directed group essays.  Finally, they must individually write a medical recommendation, which they then present to the patient (played by drama students).

The purpose of this research is fourfold.

1)      Has PBL helped students retain the same or more content as compared to the traditional lecture format?

2)      Does maintaining a journal make the content more personal and meaningful through connection to their past cognitive schema?

3)      Do students employ a variety of research skills in working towards a better understanding of the problem presented?

4)      Was each student's individual level of involvement and commitment increased as compared to a traditional lecture format?

Research

Most studies on PBL curricula have focused on the development of in-depth understanding and student-directed learning compared to the method of rote learning and memorization.  We found no research comparing retention of factual content taught through the PBL method versus more traditional methods.  Research from the University of Missouri-Columbia School of Medicine found "that students in PBL programs place more emphasis on 'meaning' (understanding) than on 'reproducing' (rote learning and memorization), and that the opposite pattern prevailed among students in traditional programs." (Vernon & Blake, 1993)  The same study found that PBL students used a greater variety of research methods (journals, online searches, and library) and were more competent in research skills.  Data showed that "student attitudes, class attendance, and student mood or distress were consistently more positive for PBL than for traditional courses or curricula." (Vernon & Blake, 1993)  The same research concluded that PBL did not produce scores as high as traditional methods on tests of basic science content.  A study conducted at the lower academic levels, high school and middle school, provided evidence that PBL students score as well as students taught traditionally.  This study indicated an increased level of student involvement, higher level critical thinking skills, and the creation of a more cooperative environment.  (Krynock & Robb, 1996).

Instructional Design

The units on human reproduction and brain structure and function in the PBL and traditional classes are conducted over a ten-day period.  The traditional classes treat these units separately, one on the nervous system and one on the human reproductive system.  Instruction is given through lectures and worksheets.  Assessment in these traditional classes is through two multiple-choice exams, each approximately 60 questions long.

In the PBL unit students are first placed in their role as doctors.  They are given personal resumes to help them connect with their roles.  Then students form "practices" of three to four doctors based on their choosing.  Students spend their class time working in their groups.  Students are given a medical file for their patient.  This file is full of history, both medical and personal, as well as the results of numerous medical tests that have been run on their patient recently.  The "doctors" analyze this file and must determine what they know and what they need to know in order to reach a diagnosis and a recommendation.  From this file, students should be able to diagnose that their patient is pregnant with a fetus suffering a severe brain abnormality.  They must then think about what they must do to find answers to what they don't know.

Some initial research from medical books and journals is given to them.   This is to prevent 150 students from descending on the local hospital library.   Students are expected to supplement this research with their own, using any means possible.   This includes library research, online research, and interviews.  Some of the research is done during class time, especially for the first few days, but much of it is done out of class.  During this time the teacher is a facilitator (like a secretary), there only to help the "doctors" complete their task.  Students keep an individual journal throughout all of their research.  In the journal they record information they have gathered and their personal reflections on what they have learned.

Students are given four directed questions to help them understand the potential problem(s) their patient faces and the variety of possible solutions.  The time frame for answering these questions is given to the students at the beginning of the project.  The group decides how the research will be done and how the questions will be answered.  These four questions are then answered as a group in essay format.

During the project the "doctors" attend a one-day "seminar" during which the teacher takes on the role of an expert in the field.  A variety of visual clarifiers to which the students would not normally have access are presented.  During this time they may ask questions of the teacher.

Final assessment of the project is based on a wide array of items.  The journals and directed questions are all assessed.  Doctors are given a "Recertification Test" pertaining to the basic biological concepts covered by this project.  However, this is only one 30-question instrument versus the two 60-question tests given to the traditional classes.  Students turn in a self and group assessment, which rates their quality of involvement within their group.  Each student must write a final recommendation to the patient outlining the diagnosis and possible treatment plans.  Finally, the class is evaluated on their meeting with the patient.  Two doctors are chosen to meet with the patient (drama students) to map out the situation and its possible solutions.

Assessment

Two questionnaires were developed and given to students currently taking the introductory Biology course and to seniors who had biology two to three years ago.  These surveys were given to students who had experienced PBL during the units covering content related to reproduction and brain structure and function and to those presented the same content in a more traditional format.  Over the last 2 years, total of 338 seniors were tested.  Of these, 123 had the PBL, 215 had not.  A total of 497 students who were currently enrolled in Biology and 230 students who were currently enrolled in Honors Biology also were tested.  All of the students in Honors Biology had the PBL as well as 188 of the students in Biology.  The other 309 students who were currently enrolled in Biology did not have the PBL.

First, students were given a content area questionnaire to check retention.  The questions for this were taken from the biology final exam to ensure that the information was encountered in all of the biology classes.  The format used was multiple choice with some use of diagrams.  Questions centered on the parts of the brain and the functions of those parts, the female and male reproductive systems and how they work, and pregnancy specific questions.  Students were asked to indicate the teacher they had for their introductory biology class so it could be determined whether the content was presented as a PBL unit or as a traditional unit.

Upon completing the content driven questionnaire, students were given the second survey that focused more on attitudes toward learning.  Students were asked to rank activities such as labs, projects, lecture, reading, and journals as to their level of effectiveness in the science learning process.  Those students that had experienced the unit as a PBL were asked further questions regarding their involvement in the learning process as a result of this type of presentation.  Types of questions centered on the development of research skills, level of personal involvement, social issues, satisfaction and stress levels, and interactions with peers and parents.  Finally, students were asked the effect of PBL on the emphasis they placed on understanding and memorization of content.

All surveys were given to students in their current science class.  No forewarning or preparation was given to students before its administration.  No effort was made to reach senior students currently not in a science class, but approximately 75% of the seniors take a science class.

Results

The results of the content test given to seniors are shown below.  Figure 1 shows the comparison of mean test scores for seniors who participated in Problem Based Learning in their introductory biology classes versus those taught by more traditional methods.  This figure also includes a comparison of seniors in AP biology (a total of XX students) and seniors not in AP biology.

Figure 2 compares these groups of students for each question on the test.  The actual test is given in Appendix I.

Figure 3 shows the comparison of mean test scores for students currently taking biology who participated in Problem Based Learning in their introductory biology classes versus those taught by more traditional methods. A distinction is made between students in Regular biology versus Honors biology.  All honors biology students have learned the content of this unit through PBL for the last two years.

Findings

Analysis of long-term retention of content indicated a significant advantage for those students who participated in Problem Based Learning versus those who were not exposed to PBL.  The mean percent for students who learned the material via PBL was 67.3% compared to 63.9% for students who learned the material in a traditional lecture-based manner, as shown in Figure 1.  Out of 19 questions the PBL students scored significantly better on 10 of the questions and marginally better on two questions, as shown in Figure 2.  These 12 questions all required some processing of information and required a greater detailed understanding of the material.  Many of them dealt with the processes involved in human reproduction or the functions of the brain rather than simply on identification of terms.  On five of the questions there was no significant difference between the two groups.  PBL students did marginally worse on one question and scored much lower on one other question.  It was interesting that this one question was a simple term question that required no processing.  These results indicate that students exposed to PBL are able to retain content knowledge more readily in the long-term when it is associated to an understanding of the entire process they studied

For students currently in the regular level introductory biology course (mostly freshman), there was a 1.8% increase in content retention for the PBL as compared to the non-PBL students, as shown in Figure 3.  Taken together with the results discussed above, this may indicate that while students do not learn more content knowledge in the PBL unit, they do not forget it as easily as those who learn it in more traditional ways.  

On the attitude survey, given in Appendix II, current students with PBL experience placed a 0higher emphasis on the importance of projects versus lecture, as shown in Table 1.  The reverse was true of the non-PBL students.  PBL students also found journaling to be much more effective in the science learning process than non-PBL students.  This may be because students not exposed to PBL have never used journals in their science classes  Seniors who had completed this PBL activity three to four years earlier placed less emphasis on lectures and ranked reading as an important learning tool for science.  This could indicate that they have realized that not all information will be given to them and that they have accepted the responsibility for gathering and processing information themselves.  Seventy percent of freshmen Honors Biology students thought projects were important in the learning process, but only 45% thought lectures were important.  Finally, 46% of this group thought journaling was very important, much higher than any other group.  Before too much weight is placed on these results, it must be noted that the freshmen Honors Biology students were given the survey upon their completion of the project whereas the other students were given the survey four months after they completed the project.  This may account for the higher results given by the Honors Biology students.

A portion of the attitude survey dealt specifically with the PBL unit.  The results are given in Table 2.  A majority of the students that had participated in this PBL project, both current and past, found that this project caused them to do the following.

v      Place more emphasis on journals, interviews, and online research with less use of the library.

v      Be more involved in the learning process and have a greater sense of satisfaction than a traditional unit.  As a result of their greater involvement and time commitment, they encountered more stress;

v      Increase their interactions with their parents.  This was especially seen in the current students due to changes in the project since the seniors had done it.

v      Formulate opinions regarding serious issues that they may encounter in the future.

v      Develop their interactions with their peer.

v      Place greater emphasis on understanding the content and less on simple memorization.

While these attitudes were not the main focus of this specific study, we feel that the use of PBL is supported by these results.  It is clearly significant that 82% of current biology students stated and 66% of the seniors remembered that this PBL unit helped them formulate opinions regarding serious issues that they may meet in the future.  Even if retention of content is the same, students are clearly gaining other skills in the PBL classroom.

References

Krynock, K.B., and Robb, L. Is Problem-based Learning a Problem for your Curriculum? Illinois School Research and Development Journal, 33(1996): 21-24.

Vernon, D. and Blake, R. Does Problem-based Learning Work? A Meta-analysis of Evaluative Research. Academic Medicine, 7(1993): 550-563.

Table 1:  Results of Attitude Survey Describing Activities Students Indicate

Help Them Learn Science*

*All values are the percent of students surveyed who responded that marked that they stated that they found these activities helpful or very helpful to them in learning science.

Table 2:  Attitude Survey Results for Items Specific to PBL Unit**

 **  Only students who participated in the PBL responded to these questions.  All values are the percent of students who responded that they agreed or strongly agreed with the statements.

!!!  PBL Teachers                                             !!!  Non PBL Teachers

Figure 1.

!!!  PBL Teachers                                             !!!  Non PBL Teachers

Figure 3