The left/right judgment task (LRJT) is enjoying popularity in clinical practices to assess and manage people with persistent pain. The LRJT has compelling theoretical underpinnings that have been tested in many painful [e.g. 2-5] and some non-painful conditions [e.g. 6-8].
LRJT software was initially created to be used on desktop computers, but we’ve gotten a little bit excited and clinical practice has outpaced research. With the advancements in technology that we’ve seen over the past decade, clinicians and researchers have jumped on the opportunity to deliver the task via mobile devices (e.g. tablets and smartphones) before we have determined whether differences in hardware (e.g. smaller images, touchscreen versus keyboard) affect the task’s validity and reliability. This is completely understandable – delivering LRJTs via mobile devices has many benefits over desktop versions. They are portable, and because so many people own smartphones these days, patients can easily download the app and practice the task at home. A win for self-management!
So, are mobile devices a valid and reliable alternative to the desktop version for LRJTs? These are important questions to answer because we need to be sure that (1) the mobile version is assessing the same construct as the desktop version (concurrent validity), and (2) there is stability in repeated assessment of the same person under the same conditions using a mobile device (test-retest reliability). We answered these question for hand, foot, back, and neck LRJTs in two healthy convenience samples (n=20 for hand images; n=37 for foot, back, and neck images). And the answer is: yes! (With a few important caveats – I’ll get to those). We found good to excellent correlations for accuracy and response times between desktop and tablet versions and for repeat tests of the tablet version (ICCs between 0.78 and 0.91). Therefore, the tablet device is a valid and reliable alternative to the desktop version.
Now for the caveats. Because we tested healthy samples, our results may not be generalisable to clinical populations. Other potential limitations of our study include overrepresentation of females, that we pooled results for different body parts, and there was a proportional bias for the reliability of neck LRJTs – these issues are discussed in detail in our paper.
Another issue is that there remains conjecture as to whether the strategy we use to perform LRJs applies across body parts. That is, for LRJs of hands and feet, the jury is pretty much in – we first make a ‘best guess’, then mentally move our own limb to match the orientation of the limb shown in the image (motor imagery) – and if our guess was right, we confirm. If our guess was wrong, we repeat the mental movement with our other limb. This is called the ‘confirmation method’. This theory of motor imagery is supported by the fact that the response times are generally proportional to actual voluntary movement; thus, we are slower to respond for more complex postures because it takes longer to mentally move our limb to match such postures. There are some pretty big datasets [e.g. 11-12] that suggest, for back and neck LRJs, the same rule seems to apply, particularly when viewing another body from behind. However, other studies have muddied the waters – for example, a recent study reported quicker response times for trunk postures with larger amplitudes of movement.. These data raise an important ‘caution’ to not presume the LRJT works in the same way regardless of body part; and we need to figure this out because if motor imagery is not taking place then the LRJT is unlikely to be clinically useful. As the saying goes… ‘more research is required!’
Nonetheless, based on our study, I think we can recommend the use of tablet devices in clinical practice and research with a reasonable degree of confidence. So, go forth and LRJT away on your mobile devices!
About Felicity Braithwaite
Dr Felicity Braithwaite is an Associate Lecturer at Flinders University and a researcher at the Body in Mind research group. She is a qualified physiotherapist, and completed her PhD with the University of South Australia in 2018. In her PhD, she focussed on improving the credibility of placebos (or ‘shams’) for physical treatments – and she enlisted the help of magicians to do so! Now, her research interests centre around pain and placebo effects. Felicity is an animal lover and was crazy enough to compete in equestrian events throughout her pre-physio life. She also loves cornflakes and beer (not together).
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