Cognitive Functioning in People With CFS: A Comparison Between Subjective and Objective Measures

[Dolphin]

A total of 54 participants were initially tested in each group; however, the Validity Indicator Profile scores of four people in each group were classified as invalid, reflecting poor effort but with an intention to perform well. These participants were excluded from all further analyses (for further details, see Cockshell & Mathias, 2012)

 

[Dolphin]

(This is just a general point, not particularly relevant to this study specifically)

and correlations of r = .1, 0.3, and 0.5 were interpreted to reflect small, medium, and large effects, respectively (Cohen, 1992).

Cohen, J. (1992). A power primer.Psychological Bulletin, 112,155–159. doi:10.1037/0033-2909.112.1.155

I'm not sure I have seen correlations graded like this before

 

[Cheshire]

reflecting poor effort but with an intention to perform well.

What does that mean? poor effort and intention to perform well seem rather antagonist.
And how do tey decide who make poor effort???

 

[Dolphin]

The mental fatigue of the CFS group was significantly greater 24 hr after testing than at the start of testing (start vs. 24 hr post, t[39]  3.59,p<.01), but this was not the case for the healthy group (start vs. 24 hr post,t[44]0.84,p=.40), indicating only the control group had recovered within this time period.

Finally, there was a significant difference in the time it took the two groups to return to their pretest mental energy levels, F(1, 71)=40.15, p < .01, with the CFS group taking an average of 57 hr (SD 46 hr; range 0 to 168 hr), compared with 7 hr for the controls (SD 10 hr; range 0 to 48 hr).

(There was a specific question asking how long it took to recover).

 

[Dolphin]

reflecting poor effort but with an intention to perform well.

What does that mean? poor effort and intention to perform well seem rather antagonist.
And how do tey decide who make poor effort???

It is not discussed in the current paper.

The abstract for that paper is:
http://www.tandfonline.com/doi/abs/10.1080/13803395.2012.668176#.U6hkp5RkTmc

 

[Dolphin]

It should be noted that people with CFS more accurately estimated their cognitive scores than the controls:

It has been suggested that people with CFS may overestimate their cognitive problems (e.g., Knoop et al., 2010; Short et al., 2002; Wearden & Appleby, 1996). However, this is not supported by Metzger and Denney (2002), Wearden and Appleby (1997), or the current study, in which the CFS group accurately evaluated their performance on two out of three tests, which was better than the controls.

 

[Dolphin]

The researchers highlight how the lack of correlation between subjective and objective measures is not unique/specific to CFS:

When considering the relationship between subjective and objective measures of cognitive functioning, it is important to note that similar findings have been reported in other groups, including healthy participants from different age groups (Mäntylä, Ronnlund, & Kliegel, 2010; Martin, 1983; Tucker-Drob, 2011), stroke patients (Duits, Munnecom, van Heugten, & van Oostenbrugge, 2008), and mild traumatic-brain-injury samples (Stulemeijer, Vos, Bleijenberg, & van der Werf, 2007); hence, this discrepancy is not unique to CFS and may indicate that they are measuring different things (Ray et al., 1993). Many questionnaires ask about general cognitive functioning (e.g., memory when doing everyday tasks), which thus has the advantage of capturing a broad range of activities and functions in a realistic environment, but may not be compatible with tests that assess specific cognitive functions in a structured and controlled test environment (Wearden & Appleby, 1996). Some researchers have dealt with this by asking questions that are more closely aligned with the tests; however, they, too, have failed to find a relationship in both CFS and control groups (Short et al., 2002; Wearden & Appleby, 1997), which may, in part, be because it is difficult to provide a rating before being exposed to the task (Short et al., 2002).

 

[Dolphin]

The authors highlight why it was unlikely correlations between subjective and objective measures would be found in this set of data:

Finally, contrary to previous research (Cockshell & Mathias, 2010), and despite carefully selecting the tests for the current study, the CFS participants did not show deficits on tests of memory and attention, which restricted the range of scores on these measures, and, hence, the likelihood of finding a relationship between our subjective and objective measures. Indeed, this sample only showed evidence of impaired information processing speed on a RT task (Cockshell & Mathias, 2013), but because reduced speed is not central to the diagnosis of CFS, we did not include self-report measures of this construct and so are unable to determine whether subjective and objective assessments of speed are related.