An Australian study used the Validity Indicator Profile (VIP) to examine whether reduced effort contributes to the cognitive deficits that are associated with CFS.
Unlike most tests of effort, the VIP distinguishes between intentional and unintentional poor performance and does not assess cognitive functions that are affected by CFS, thereby reducing the risk of mistakenly attributing genuinely poor performance to reduced effort.
VIP performance was classified as valid for the majority of participants (CFS and controls), indicating high levels of effort and an intention to perform well.
No participant performed in a manner indicative of an intent to perform poorly (invalid: suppressed, inconsistent).
These findings suggest that poor effort is unlikely to contribute to cognitive test performance of persons with CFS.