I have never bothered to record the daily variation in my moods, for fear that the effort would damage the frailty of my good humour and cast me into even deeper despair. At a gut level, or perhaps that should be a gut-wrenching level, we all seem to have good days and bad days. Some days proceed from defeat to defeat like ink spreading across a damask table cloth. Others (less frequent) soar above earthly concerns to deliver joyous triumphs and accolades. Raise high the roof-beams, carpenters!
Does any of this emotional tittle tattle and swooning effluvia have any effect on serious things like intellectual performance? It seems so. You may remember Sophie von Stumm, who showed that the Dunning-Kruger effect affects people’s self-assessments of their own intellectual abilities:
Here is what she has found when she subjects volunteers to up to 5 days of intellectual testing.
DAY-TO-DAY VARIABILITY IN IQ AND MOOD Sophie von Stumm
Goldsmiths University of London,
Intelligence, also known as IQ, has been shown to be subject to systematic developmental changes in childhood and in late life and to be relatively stable from adolescence through most of adulthood. However, little is known about the stability – or in fact variability – of cognitive functioning and intelligence test performance across days. Here, the day-to-day variability across 6 IQ tests was studied and its associations with a) day-to-day variability in mood and b) personality traits.
Overall 98 participants (age range 18 to 75, mean 23 years) were assessed 5 times on 5 consecutive days in the lab, where they completed each day different versions/ items of 6 cognitive ability tests (short-term memory, logical reasoning, image rotation, pattern comparison, working memory, processing speed) and the Positive and Negative Affect Scale (PANAS). On day 1, they also completed the NEO-FFI to assess the Big Five.
All participants completed at least 2 study days, and 77 participants contributed on all 5 study days. Day-to-day variance in mood and cognitive ability tests were adjusted for trial-to-trial variance (i.e. within-test variance/ internal consistency). Day-to-day variability in cognitive ability tests ranged in IQ points (mean 100, SD = 15) from 0 to 20 with an average of approximately 6 IQ points across tests (SD = 3), demonstrating a) considerable day-to-day variability in cognitive function and b) individual differences in day-to-day variability. Associations between individual differences in the extent of day to-day variability in cognitive function and mood were weaker than their respective correlations with personality traits.
This study demonstrates the extent of day-to-day variability in IQ and mood, thereby highlighting the importance of the individual differences dimension of variability per se. In addition, the findings help understanding the relative importance of more (i.e. mood) and less (i.e. personality) fluctuating factors for variability in cognitive ability test performance.