I will be honest—the first time I heard of problem-based learning (PBL) was in 1993 when I was writing my teaching report as a part of my tenure exercises as an associate professor at the Universitat Autònoma de Barcelona (UAB). I had never had training in teaching or pedagogy at the college level. Therefore, I was surprised to read about a method where a group of students worked together with a tutor to analyze cases, with the students generating their own questions and finding the answers by themselves. At the time, this seemed like an impossible way of teaching—a craziness of Anglo-Saxon countries that could never to be applied to my university, settled in a Latin country with very different teaching traditions.
To help you understand my feelings at that time, first let me introduce myself. I am an MD who completed a residence in clinical pharmacology and obtained a PhD in pharmacology. My focus was on the physiology of the skeletal neuromuscular junction. After my PhD, I took up a post as an assistant professor. I was trying for a tenured position when I read about the PBL stuff that started at McMaster University and was later adopted at Maastrich University. As I worked through my tenure application, I wondered how PBL actually worked, but I soon forgot about these ponderings after I received tenure. My interest was not renewed until a few years later.
In 1996, when I was President of the Catalonian Society of Pharmacology, a friend of mine at the Veterinary School of UAB asked me if a visiting professor from McMaster University could be invited by the Society to give a lecture on the way PBL changed his university. I was intrigued because I remembered my readings on the method, and I quickly accepted the proposal. The professor was Edwin E. Daniel. I chaired the session and was very impressed by his account of how everything started in McMaster’s Honours Biology and Pharmacology Programme. In the dinner that followed, I asked Edwin more about the implementation of PBL and explained my prior interest in the method. Unexpectedly, he invited me to Hamilton to see for myself how everything worked. He also told me about a course that was scheduled for the following November for foreign professors that centred around the PBL teaching method. The invitation was one that I could not resist: to receive formal training and to see the PBL method in action. I am still in debt to Edwin for his invitation, which changed my way of teaching in the years that followed. So, I got myself organized and packed my things. At McMaster, I made friends that I still have today. First, Patangi Ranchagari (Chari), who has had great influence on me since then. Second, the director of the course, Luis Branda, who I later met in Barcelona and with whom I edited a book on PBL in health sciences . Unfortunately, he passed away two years ago.
Let’s follow my journey with PBL step-by-step.
I came to McMaster in the autumn of 1996. In addition to any exposure I might have during the course for foreign professors, I asked if I could attend some PBL tutorials during my stay, so Edwin introduced me to some of the PBL tutors at the university. I attended lectures led by Luis, as well as tutorials led by other members of faculty. I still remember the first tutorial with Denis J. Crankshaw, which I attended as a guest. The problem that the students were tackling was about an obese guy working in the field of eating disorders. The students, who were in their first year of the Honours Biology and Pharmacology Programme and were in their second tutorial session, had already gathered information about the case. In this session, the students talked about how eating is controlled using papers published in Science. I was in shock. What? First year pharmacology students were reading (and understanding) articles in first-line journals and were able to discuss them? I wondered if I was experiencing the effects of some unexpected psychedelic drugs. In my lectures and seminars, students were completely passive—they never read papers from journals, at least not as undergraduates. How was all of this possible?
My shock continued into the next day when I assisted in a tutorial of first year medical students. I was waiting at the door of the classroom when the tutor appeared with a coffee mug and a doughnut in his hands. I introduced myself and entered the room. A group of students were there, ready to begin. The tutor gave me a piece of paper upon which the problem was written. It was centred on a girl with diabetes who was in a ketoacidosis-induced coma; her diabetes had been overlooked until then. Students started to analyze the case, considering the physiology of carbohydrate regulation, the role of insulin, the pathophysiology of diabetes, the effect of diabetes on fatty acid metabolism, metabolic acidosis, and the resulting hyperventilation. I was completely astounded and unable to come to terms with what I was observing. While the students explained their findings and their reasoning, the tutor drank his coffee and ate his doughnut. What kind of teaching was this, I thought, with the students doing all the talking and the teacher only observing and not saying anything? To be fair, the students did occasionally ask for the tutor’s approval of their reasoning, to which the tutor would respond by moving his head.
My third episode of shock occurred when I attended Chari’s tutorial. Given my background in pharmacology, I was interested when he explained that the problem in question was a case about drug metabolism—I wondered how PBL could be used to teach pharmacology. The students analyzed a case where a fluoroquinolone antibiotic was causing sleep problems in a man who drank several cups of coffee each day. When the antibiotic was changed to another of the same family, his sleep problems disappeared. I was surprised to see how well the students coped with the complex problem and how they were able to arrive at an understanding of the reason for the man’s problem. Better still, the students were able to use their new knowledge to understand how differences in drug metabolism can explain some unexpected drug effects. Impressive.
My final experience with PBL occurred during a visit to Harvard Medical School while I was still at McMaster. Harvard had started the New Path, which introduced PBL in the preclinical years of medical training. I had read a book by the Dean at the time, Daniel C. Tosteson, about Harvard’s experience with the New Path, which prompted me to ask him if I could pay a visit to see how it worked. When I arrived, Dr. Miriam Wetzel from the Office of Educational Development cordially received me and explained the program. She even invited me to an evening dinner during which professors from the School of Medicine prepared PBL activities for the following months. I still remember the discussion about the new problems, as well as the PBL exercise that the tutors themselves undertook that addressed some of the common problems that PBL tutors encounter with their students. This was a new, inspiring experience for a naïve teacher—I was most definitively in love with PBL. I often liken my transformation to the conversion of Saint Paul to the Christian religion. Saint Paul was a strong persecutor of Christians until, when on his way to Damascus, he heard the voice of God who told him, “Paulus, Paulus, why are you persecuting me?” When Saint Paul heard this voice, he fell to the ground, and from then on, he was a pious follower of the Christian God. I felt in the same way. I was completely taken by PBL. For now.
After two weeks at McMaster, I returned to Barcelona. On the return flight, I thought about how I could apply PBL to my teaching. I was certain that changing the curricula of UAB to PBL would be impossible. What, then, could be done? Several weeks later, I had the opportunity to give a seminar to my colleagues on my experiences in Hamilton and Boston. The seminar was a failure. My colleagues looked at me as though I was a crazy or, even worse, that I was foolish. Nobody seemed interested in the method, with the exception of a few friends in my department. I was not sure if their support was about friendship or a genuine interest in PBL. I had planned to start a sabbatical year, so I forgot about PBL for a while.
In August 1997, I began a sabbatical year at the Allegheny University of Health Sciences (now Drexel University) in Philadelphia. My goal was to learn about experimental models of neuropathic pain in the lab of Dr. Gary Bennett, who had recently moved from Bethesda. As a visiting scientist, one typically has plenty of time to work in the lab, to read, to write—and most importantly, to think. At that time, PBL came to my mind and I asked myself again how I could use it in my teaching. It was then that I had an idea that changed everything for me. Why not use PBL as a teaching method, rather than changing the whole curriculum of my university? The idea was mature when I returned to Barcelona in September 2018.
I suggested to my colleagues that they use PBL as a teaching method in Pharmacology courses that had a practical nature. This suggestion received positive attention because medical students generally dislike lab activities involving rats, and by that time, the use of animals was very restricted. PBL—although modified from the ‘pure’ model of McMaster—offered an excellent alternative approach to practical training. Although we did not use PBL as the primary model for disseminating knowledge in our courses, we did adopt a hybrid model in which lectures remained and PBL tutorials were used to discuss and deepen the students’ knowledge through critical analysis, the search for information, and summary discussions. Towards this aim, we chose topics that were difficult to understand in lectures, such as the pharmacology of cholinergic and adrenergic drugs or the mechanisms of non-steroidal anti-inflammatory agents. The tutorials were organized as three-hour seminars, during which the group would read and discuss a problem, identify relevant questions and gaps in knowledge, and would then go to the library to find answers. The session finished when students reported their findings, shared with the other members of the group, and, finally, discussed as a group the answers to the questions that they had initially proposed. The tutor acted as a facilitator of the process, asking the right questions to test the knowledge of the students, but outside of the traditional role of teacher. These tutorial experiences were very successful. In the end, the students were so pleased with the process that they requested an increase in the time devoted to these types of tutorials and a decrease in the number of lectures. We published two papers describing our approach ; the results of a survey of student satisfaction  was published at the same time.
In 2002, I moved to the Universitat Pompeu Fabra (UPF), taking on the role of professor in the new Bachelor of Biology Program that had started four years prior. My main task was to contribute to organizing the professional tracks in the fifth year of the program. The goal was to provide an opportunity for students to gain some professional experience before graduation . PBL was integrated into the new curriculum alongside lectures, seminars, and internships in research units, clinical laboratories, or at pharmaceutical companies. Students welcomed PBL tutorials, which they scored the highest in terms of their value relative to other teaching activities . By 2006, we had started a Master’s program that also incorporated PBL activities, as well as lectures, seminars, and internships at pharmaceutical companies. We are still following this approach thirteen years later.
In 2004, Catalonian universities started on a path towards the European Higher Education Area (EHEA), an agreement of European Governments to converge to a common university system to improve the competitiveness of European universities in a global environment. To this end, UPF started pilot studies in which we adopted new teaching paradigms. Our strategy was to introduce PBL as a teaching method in each subject, and to write problems that shared educative objectives with several of them, while also maintaining traditional teaching activities. Some of the time that was historically devoted to traditional teaching activities shifted to PBL activities. This new approach required the participation of many teachers from different disciplines, all of whom required training in the PBL teaching method. During training, potential tutors learned about PBL, they wrote problems together, and they agreed upon evaluation methods. In the end, a huge number of tutors were trained, allowing PBL to successfully integrate into the overall teaching strategy of the school. The pilot project ended in 2012, and the new curricula—which followed EHEA guidelines—were implemented at UPF.
The implementation of the EHEA curricula began in 2008. Our experience in the pilot studies taught us several lessons. First, teachers were reluctant to reduce their traditional curriculum content to allow integration with other disciplines. Second, the students were not happy with the evaluation criteria, which, in their opinion, did not fairly align with the effort and time that they devoted to PBL activities. However, several studies showed that PBL activities, even when used as part of a hybrid approach, enhanced the long-term knowledge of the students [6,7]. Students and teachers agreed that PBL activities improved the knowledge and development of soft skills . We concluded that the hybrid approach was a success, but we needed a new strategy that permitted full acceptance by teachers and students. This led to the development of subjects that used PBL to integrate knowledge across disciplines. We called these subjects ‘Integrated Medicine’ and ‘Integrated Biomedicine’ in our Bachelors of Medicine and Human Biology programs, respectively.
These new subjects were designed to allow the use of the PBL approach in the first three (Human biology) or four (Medicine) years of the curricula. Their content was interdisciplinary and included knowledge from all disciplines. The courses were delivered exclusively by PBL, and cases were built with common educative objectives and were written by tutors using a consensus approach. In the case of medical students, basic and clinical content was included in every problem, starting in the first year of the curriculum. This new era started in 2008. A survey carried out six years later (the year that the first cohort of medical students graduated) showed that students considered these activities of high value, helping them to enhance their understanding during clinical training .
What have I learned after all these years? First, the implementation of PBL is not easy and teachers are reluctant to accept this approach, especially in universities that have a long history of using traditional teaching approaches. Second, a concerted and significant effort is needed to train teachers in the PBL. Third, when a full curriculum in PBL is not feasible, a hybrid approach is a good alternative. Fourth, students express a high satisfaction after being trained using PBL, and they feel that this approach helps them acquire soft skills and improve their ability to understand complex issues. For all of these reasons, I believe that PBL is one of the best methods to learn how to learn. This is the main reason why I am still in love with PBL, twenty years later.
 Carrió M, Branda L, Baños JE (dir.). El aprendizaje basado en problemas en sus textos. Ejemplos de su empleo en biomedicina. Barcelona: Fundació Dr. Antoni Esteve, 2013.
 Baños JE. (2001). El aprendizaje basado en problemas en los planes de estudio tradicionales: ¿una alternativa posible? Educ Med 4: 4–12.
 Vivas NM, Badia A, Vila E, Baños JE. (2001). El aprendizaje basado en problemas como método docente en Farmacología: la opinión de los estudiantes de Medicina. Educ Med 4: 194–201.
 Aramburu J, Bosch F, Sentí M, Baños JE. (2006). Los itinerarios profesionales en Biología: un ejemplo de formación académica orientada a la inserción profesional. Educ Med 9: 23–30.
 Bosch F, Baños JE. (2010). Tendiendo puentes: la utilidad de la historia de la ciencia para comprender el proceso de investigación y desarrollo de medicamentos. Educ Med 13: 255–62.
 Carrió M, Larramona P, Baños JE, Pérez J. (2011). The effectiveness of hybrid problem-based learning approach in the teaching of biology: a comparison with lecture-based learning. J Biol Educ i: 1–7
 Carrió M, Agell L, Baños JE, Moyano E, Larramona P, Pérez J. (2016). Benefits of using a hybrid problem-based learning curriculum to improve long term learning acquisition in undergraduate biology education. FEMS Microbiol Letters 6363: 1-7.
 Carrió M, Larramona P, Pérez J, Baños JE. (2018). Percepciones de estudiantes y docentes sobre la implementación del aprendizaje basado en problemas como método docente. FEM 21: 143–152.
 Sentí M, Bigorra J, Samsó E, Minguella J, Miralles R, Girvent M, Solsona JF, Baños JE. (2015). A collaborative project to bridging the gap between basic and clinical sciences: The opinion of medical students. J Biomed Educ vol. 2015, Article ID 620348.