Chances are You Know Half as Much as You Did 7 Years Ago: Half-Life of Knowledge Underscores the Importance of Continued Professional Development

HalfLifeThe half-life of knowledge is an interesting and important concept. Half-life of knowledge refers to the number of years that it would take for half of the information or knowledge available in a field of study to become defunct or superseded by new information.  This number, of course, varies by field or specialized area of study. The half-life of knowledge for two well-developed areas of medical specialization—hepatitis and cirrhosis—has been calculated to be about 45 years. That is, it takes about 45 years for half of the current knowledge base in these areas to become outdated and superseded by new information.

Half-Life of Knowledge for Forensic Psychology

The half-life for information in the field of psychology (broadly defined) has been calculated to be about 7.2 years, with wide variation depending upon area of specialization. For example, the half-life of knowledge in the area of psychoanalytic psychology, an established area with relatively little new research, has been estimated at 15.6 years whereas the half-life for psychopharmacology, a relatively new field with burgeoning research, has been estimated at 4.8 years.

The half-life for information relevant to forensic psychology is currently estimated to be 7.5 years and for police psychology to be 8.3 years. Estimates of the future half-life of these specializations are 6.6 years for forensic psychology and 7.2 years for police psychology. Thus, without any additional professional training or development, our knowledge base falls to about 50% within a 7-year period.

Rapid developments in our knowledge and skill sets underscore the importance of keeping up to date with the research for implementation into practice. A cursory review of the research literature in the area of risk assessment shows that we have gone from thinking about dangerousness, to the importance of empirically established risk factors, to the relevance of risk communication, to models of structured professional judgment that highlight the management of risk factors, all within the last two decades.

Similarly, our knowledge and practice with respect to competency evaluation has evolved as a result of a more nuanced interpretation of the standards set out in dicta from case law and Supreme Court decisions and best practices standards published over the last several years.

Information regarding the half-life of knowledge serves to underscore the importance of continued professional development. In the field of psychology, for example, doctoral programs are designed to provide a broad and general foundation of knowledge and skills, with the expectation that graduates will then continue to develop and build upon this foundation through additional specialized professional training and continuing education endeavors. The same is true for the medicine and other professional fields.

Problem-Based Learning for Professional Development

The field of medicine has widely adopted a “problem-based learning” (PBL) model of continuing professional development. The PBL model emphasizes the development of clinical reasoning skills and self-directed learning through the use of clinical case presentations, which allow the opportunity for professionals to apply new skills or techniques to real cases. In addition, the use of an online format for much continuing medical education allows for worldwide dissemination of this training, eliminates the need to travel to obtain further professional development, allows the professional to work at his or her own pace, and makes training by the best of the best accessible to all.

Problem-based learning using an online format has only recently been applied to other fields, such as clinical and forensic psychology, but initial evaluation efforts undertaken in Australia and the United States show positive results and conclude that online problem-based learning can make a significant contribution to professional development.

Professional training programs that allow the opportunity to apply new knowledge and skills to case studies and case illustrations similar to those encountered in one’s professional practice are important for continued professional development and serve to enhance clinical reasoning and case formulation skills. Given the half-life of knowledge, it is imperative that professionals make a concerted effort to stay on top of recent developments in research and practice. Seeking out professional development or training opportunities (either in-person or online) on a regular basis will serve to minimize the chance of using outdated information or being left behind.

Professional Training Programs

CONCEPT has developed a series of problem-based online professional training programs that are currently enrolling for an early 2014 start. If you have ideas or suggestions for additional training programs, please let us know. If you are a senior-level graduate student and would like to apply for a scholarship for one of our training programs, please apply here.


Kiernan, M. J., Murrell, E., & Relf, S. (2008). Professional education of psychologists using online problem-based learning methods: Experience at Charles Sturt University. Australian Psychologist, 43, 286-292.

Neimeyer, G. J., Taylor, J. M., & Rozensky, R. H. (2012). The diminishing durability of knowledge in professional psychology: A Delphi Poll of specialties and proficiencies. Professional Psychology: Research and Practice, 43, 364-371.

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