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Een fMRI wordt vaak gebruikt bij hersenonderzoek. Toch blijkt het een weinig betrouwbare methode te zijn: er is een overlap van 30% en een correlatie van 0,5 (1 = perfect betrouwbaar; 0 = helemaal niet betrouwbaar).

Betrouwbaarheid houdt in dat iemand anders die diezelfde meting doet, perfect hetzelfde resultaat zou bekomen. Of, zoals het hier omschreven wordt:

For example, if you're measuring an adult's height you want to make sure that your tape measure gives you similar results each time you use it on the same person. Of course, you may have readings that vary by a millimetre or two each time, but if you get wildly different results on Monday and Tuesday, you probably want to bin your tape measure.

Toegepast op een fMRI wordt dit:

In fMRI there are two types of results. One is 'where in the brain' and the other is 'how strong' is the activity.

We can examine the first by looking at how well the active brain areas overlap in scans taken at two different times, and we can examine the second by looking at the similarity of the strength of the results using a statistical test like a correlation.

The better the overlap and the statistical relationship between the results from the same test on the same people at different times, the more we can rely on our measurement technique.

This new analysis reviewed all the previous studies that have looked at the test-retest reliability of fMRI and found that overall, active brain areas overlap about 30% of the time and the correlation for the strength of the activity was about 0.5....

Toch betekent dit niet dat een fMRI weinig te bieden heeft. Als steeds weer hetzelfde fenomeen wordt gemeten dmv. een fMRI, zal uiteindelijk duidelijk worden welke factoren er steeds weer bevestigd worden en welke niet.

... One thing is abundantly clear: fMRI is an effective research tool that has opened broad new horizons of investigation to scientists around the world. However, the results from fMRI research may be somewhat less reliable than many researchers implicitly believe. While it may be frustrating to know that fMRI results are not perfectly replicable, it is beneficial to take a longer-term view regarding the scientific impact of these studies. In neuroimaging, as in other scientific fields, errors will be made and some results will not replicate. Still, over time some measure of truth will accrue. This chapter is not intended to be an accusation against fMRI as a method. Quite the contrary, it is meant to increase the understanding of how much each fMRI result can contribute to scientific knowledge....

uit (full text): Bennett, C. M., & Miller, M. B. (2010) How reliable are the results from functional magnetic resonance imaging?. Annals of the New York Academy of Sciences

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