Quantitative Versus Qualitative



Practical Detection of Faking 101

My first meeting with a physiatrist (a physician specializing in rehabilitation or physical medicine) was with a gentleman with 40 years experience. I was waiting in his outer office for him to finish his examination of a patient. After a few minutes, while in his office discussing the system that he wanted designed, he said: "Follow me." We walked to another office which overlooked the street and he continued to discuss our collaboration while staring out the window. I thought to myself what a strange way to conduct a first meeting when all of a sudden he exclaimed "I knew it!"


He continued: "When she was in my office she complained that it hurt wherever I touched her. The pattern made no sense. I suspected that she was faking her injuries for the insurance money. In the office she could barely walk, but I just saw her walk down the street without a problem." This was my introduction to faking an injury for money. This is an area where the ability to quantify human performance (see qualitative versus quantitative measurements) can aid in the detection of faking.


Qualitative Versus Quantitative Measurements

In the evaluation of muscle strength, performance is often measured subjectively or qualitatively. Gross scales are used to measure performance such as good, fair, poor. Some clinicians (e.g. physicians, physical and occupational therapists) feel that they can track a patientās progress using such a system. Even if an experienced clinician can evaluate the changes of a patientās progress manually (i.e. without a device for quantitative measurement), there are many advantages of quantitative measurements. Here are a few:

Provides an objective measure.

Allows for other clinicians to continue an individualās treatment. If a qualitative measurement system is used, a score such as "fair" may have different meanings.

Include biofeedback, such as a display to show the current level of effort.

Detect changes to subtle to be perceived manually.

Improved inter- and intra-tester reliability.

For electronic systems, database and report generation features.

Detection of faking can be greatly enhanced. For example, if a person is asked to exert maximum force during a test while watching a readout, and then the readout is removed, the person will continue to exert a force in a predictable fashion. If the person is faking by trying to exert only half of the maximum strength, when the readout is removed, the output will vary greatly. This is due to the difficulty of exerting a set level of force without feedback lower than maximal.

Very important for research studies.


Static Versus Dynamic Biofeedback: An Example

After surgery on a leg or hip, it may be desirable to reduce the forces due to walking by using a cane or crutches. If the dynamic forces are too large, the body can be reinjured. However, if little or no force is exerted on the leg or hip, the healing process may be slowed.


Problem: If it is desirable to place say 20% of the dynamic and static body weight on the injured side of the body while using crutches, how would you train the patient?


Potential Solution 1: Have the patient stand with each foot on a different scale and practice shifting the body weight.


Comments: This is an inexpensive approach. Will this give the patient any idea about the dynamic weight distribution while walking?


Potential Solution 2: Use what is referred to as a "limb load monitor." Place a thin force sensor under each foot. While walking, have it emit a high tone when too much weight has been exerted on the injured side and a low tone when too little force has been applied.


Comments: More expensive, but may lead to a shorter training period and a lower risk of injury.


Return to Brief Review

Support for the development of this module was provided by the National Science Foundation and The Cooper Union for the Advancement of Science and Art.

Please send questions or comments to Professor Ron Adrezin or Professor Daniel Raichel.