Placebo effects in cognitive training

Edited by Michael S. Gazzaniga, University of California, Santa Barbara, CA, and approved May 17, 2016 (received for review January 22, 2016)
June 20, 2016
113 (27) 7470-7474

Significance

Placebo effects pose problems for some intervention studies, particularly those with no clearly identified mechanism. Cognitive training falls into that category, and yet the role of placebos in cognitive interventions has not yet been critically evaluated. Here, we show clear evidence of placebo effects after a brief cognitive training routine that led to significant fluid intelligence gains. Our goal is to emphasize the importance of ruling out alternative explanations before attributing the effect to interventions. Based on our findings, we recommend that researchers account for placebo effects before claiming treatment effects.

Abstract

Although a large body of research shows that general cognitive ability is heritable and stable in young adults, there is recent evidence that fluid intelligence can be heightened with cognitive training. Many researchers, however, have questioned the methodology of the cognitive-training studies reporting improvements in fluid intelligence: specifically, the role of placebo effects. We designed a procedure to intentionally induce a placebo effect via overt recruitment in an effort to evaluate the role of placebo effects in fluid intelligence gains from cognitive training. Individuals who self-selected into the placebo group by responding to a suggestive flyer showed improvements after a single, 1-h session of cognitive training that equates to a 5- to 10-point increase on a standard IQ test. Controls responding to a nonsuggestive flyer showed no improvement. These findings provide an alternative explanation for effects observed in the cognitive-training literature and the brain-training industry, revealing the need to account for confounds in future research.

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Data Availability

Data deposition: The data have been achived on Figshare, https://figshare.com/articles/Placebo_csv/2062479.

Acknowledgments

This work was supported by George Mason University; the George Mason University Provost PhD Awards; Office of Naval Research Grant N00014-14-1-0201; and Air Force Office of Scientific Research Grant FA9550-10-1-0385.

Supporting Information

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References

1
Selk J (2013) Amidst billion-dollar brain fitness industry, a free way to train your brain. Forbs. Available at www.forbes.com/sites/jasonselk/2013/08/13/amidst-billion-dollar-brain-fitness-industry-a-free-way-to-train-your-brain/#6b3457647d41. Accessed May 8, 2016.
2
AK Shapiro Handbook of Psychotherapy and Behavior Change (Wiley, New York, 1971).
3
JA Turner, RA Deyo, JD Loeser, M Von Korff, WE Fordyce, The importance of placebo effects in pain treatment and research. JAMA 271, 1609–1614 (1994).
4
Jr TJ Bouchard, DT Lykken, M McGue, NL Segal, A Tellegen, Sources of human psychological differences: The Minnesota Study of Twins Reared Apart. Science 250, 223–228 (1990).
5
R Plomin, NL Pedersen, P Lichtenstein, GE McClearn, Variability and stability in cognitive abilities are largely genetic later in life. Behav Genet 24, 207–215 (1994).
6
L Larsen, P Hartmann, H Nyborg, The stability of general intelligence from early adulthood to middle-age. Intelligence 36, 29–34 (2008).
7
SM Jaeggi, M Buschkuehl, J Jonides, WJ Perrig, Improving fluid intelligence with training on working memory. Proc Natl Acad Sci USA 105, 6829–6833 (2008).
8
SM Jaeggi, et al., The relationship between n-back performance and matrix reasoning—Implications for training and transfer. Intelligence 38, 625–635 (2010).
9
SM Jaeggi, M Buschkuehl, J Jonides, P Shah, Short- and long-term benefits of cognitive training. Proc Natl Acad Sci USA 108, 10081–10086 (2011).
10
SM Jaeggi, M Buschkuehl, P Shah, J Jonides, The role of individual differences in cognitive training and transfer. Mem Cognit 42, 464–480 (2014).
11
SR Rudebeck, D Bor, A Ormond, JX O’Reilly, AC Lee, A potential spatial working memory training task to improve both episodic memory and fluid intelligence. PLoS One 7, e50431 (2012).
12
M Strenziok, et al., Neurocognitive enhancement in older adults: Comparison of three cognitive training tasks to test a hypothesis of training transfer in brain connectivity. Neuroimage 85, 1027–1039 (2014).
13
U Neisser, et al., Intelligence: Knowns and unknowns. Am Psychol 51, 77–101 (1996).
14
MW Watkins, P-W Lei, GL Canivez, Psychometric intelligence and achievement: A cross-lagged panel analysis. Intelligence 35, 59–68 (2007).
15
FL Schmidt, JE Hunter, The validity and utility of selection methods in personnel psychology: Practical and theoretical implications of 85 years of research findings. Psychol Bull 124, 262–275 (1998).
16
LS Gottfredson, Intelligence: Is it the epidemiologists’ elusive “fundamental cause” of social class inequalities in health? J Pers Soc Psychol 86, 174–199 (2004).
17
LS Gottfredson, IJ Deary, Intelligence predicts health and longevity, but why? Curr Dir Psychol Sci 13, 1–4 (2004).
18
LJ Whalley, IJ Deary, Longitudinal cohort study of childhood IQ and survival up to age 76. BMJ 322, 819 (2001).
19
BI O’Toole, L Stankov, Ultimate validity of psychological tests. Pers Individ Dif 13, 699–716 (1992).
20
SJ Ceci, WM Williams, Schooling, intelligence, and income. Am Psychol 52, 1051–1058 (1997).
21
T Strenze, Intelligence and socioeconomic success: A meta-analytic review of longitudinal research. Intelligence 35, 401–426 (2007).
22
SL Willis, et al., Long-term effects of cognitive training on everyday functional outcomes in older adults. JAMA; ACTIVE Study Group 296, 2805–2814 (2006).
23
TL Harrison, et al., Working memory training may increase working memory capacity but not fluid intelligence. Psychol Sci 24, 2409–2419 (2013).
24
TS Redick, et al., No evidence of intelligence improvement after working memory training: A randomized, placebo-controlled study. J Exp Psychol Gen 142, 359–379 (2013).
25
J Au, et al., Improving fluid intelligence with training on working memory: A meta-analysis. Psychon Bull Rev 22, 366–377 (2015).
26
J Karbach, P Verhaeghen, Making working memory work: A meta-analysis of executive-control and working memory training in older adults. Psychol Sci 25, 2027–2037 (2014).
27
MR Dougherty, T Hamovitz, JW Tidwell, Reevaluating the effectiveness of n-back training on transfer through the Bayesian lens: Support for the null. Psychon Bull Rev 23, 306–316 (2016).
28
PM Greenwood, R Parasuraman, The mechanisms of far transfer from cognitive training: Review and hypothesis. Neuropsychology, November 16, 2015).
29
WR Boot, DJ Simons, C Stothart, C Stutts, The pervasive problem with placebos in psychology: Why active control groups are not sufficient to rule out placebo effects. Perspect Psychol Sci 8, 445–454 (2013).
30
M Melby-Lervåg, C Hulme, Is working memory training effective? A meta-analytic review. Dev Psychol 49, 270–291 (2013).
31
M Melby-Lervåg, C Hulme, There is no convincing evidence that working memory training is effective: A reply to Au et al. (2014) and Karbach and Verhaeghen (2014). Psychon Bull Rev 23, 324–330 (2016).
32
Z Shipstead, TS Redick, RW Engle, Is working memory training effective? Psychol Bull 138, 628–654 (2012).
33
WR Boot, DP Blakely, DJ Simons, Do action video games improve perception and cognition? Front Psychol 2, 226 (2011).
34
C Dweck Self-Theories: Their Roles in Motivation, Personality, and Development (Psychology Press, New York, 2000).
35
FJ Evans, The placebo response in pain reduction. Adv Neurol 4, 289–296 (1974).
36
R Hossiep, D Turck, M Hasella Bochumer Matrizentest (BOMAT) Advanced (Hogrefe, Goettingen, Germany, 1999).
37
JC Raven, JH Court, J Raven, H Kratzmeier Advanced Progressive Matrices (Oxford Psychologists Press, Oxford, 1994).
38
JC Raven, JH Court Raven’s Progressive Matrices and Vocabulary Scales (Oxford Psychologists Press, Oxford, 1998).
39
MC Frey, DK Detterman, Scholastic assessment or g? The relationship between the Scholastic Assessment Test and general cognitive ability. Psychol Sci 15, 373–378 (2004).
40
J Raven, JC Raven, JH Court Manual for the Raven’s Progressive Matrices and Vocabulary Scales (Oxford Psychologists Press, Oxford, 1998).
41
JT Cacioppo, RE Petty, The need for cognition. J Pers Soc Psychol 42, 805–818 (1982).
42
DJ Torgerson, J Klaber-Moffett, IT Russell, Patient preferences in randomised trials: Threat or opportunity? J Health Serv Res Policy 1, 194–197 (1996).
43
RM Ryan, MF Lynch, M Vansteenkiste, EL Deci, Motivation and autonomy in counseling, psychotherapy, and behavior change: A look at theory and practice. Couns Psychol 39, 193–260 (2010).
44
; Stanford Center on Longevity, A consensus on the brain training industry from the scientific community. Available at longevity3.stanford.edu/blog/2014/10/15/the-consensus-on-the-brain-training-industry-from-the-scientific-community-2/. Accessed May 8, 2016. (2014).
45
; Cognitive Training Data, Open letter response to the Stanford Center on longevity. Available at www.cognitivetrainingdata.org/. Accessed May 8, 2016. (2015).
46
; Federal Trade Commission, Lumosity to pay 2$ million to settle FTC deceptive advertising charges for its “brain training” program. Available at https://www.ftc.gov/news-events/press-releases/2016/01/lumosity-pay-2-million-settle-ftc-deceptive-advertising-charges. Accessed May 8, 2016. (2016).
47
; Open Science Collaboration, PSYCHOLOGY. Estimating the reproducibility of psychological science. Science 349, aac4716 (2015).

Information & Authors

Information

Published in

Go to Proceedings of the National Academy of Sciences
Go to Proceedings of the National Academy of Sciences
Proceedings of the National Academy of Sciences
Vol. 113 | No. 27
July 5, 2016
PubMed: 27325761

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Data Availability

Data deposition: The data have been achived on Figshare, https://figshare.com/articles/Placebo_csv/2062479.

Submission history

Published online: June 20, 2016
Published in issue: July 5, 2016

Keywords

  1. placebo effects
  2. cognitive training
  3. brain training
  4. fluid intelligence

Acknowledgments

This work was supported by George Mason University; the George Mason University Provost PhD Awards; Office of Naval Research Grant N00014-14-1-0201; and Air Force Office of Scientific Research Grant FA9550-10-1-0385.

Notes

This article is a PNAS Direct Submission.

Authors

Affiliations

Department of Psychology, George Mason University, Fairfax, VA 22030
Samuel S. Monfort
Department of Psychology, George Mason University, Fairfax, VA 22030
Martin Paczynski
Department of Psychology, George Mason University, Fairfax, VA 22030
Patrick E. McKnight
Department of Psychology, George Mason University, Fairfax, VA 22030
P. M. Greenwood
Department of Psychology, George Mason University, Fairfax, VA 22030

Notes

1
To whom correspondence should be addressed. Email: [email protected].
Author contributions: C.K.F. designed research; C.K.F. and S.S.M. analyzed data; and C.K.F., S.S.M., M.P., P.E.M., and P.M.G. wrote the paper.

Competing Interests

The authors declare no conflict of interest.

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    Placebo effects in cognitive training
    Proceedings of the National Academy of Sciences
    • Vol. 113
    • No. 27
    • pp. 7285-E3987

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