In the summer of 2009 I tried to cure homemade sausages in my kitchen. One of the hazards of such a practice is preventing the growth of undesirable molds and diseases such as botulism. My wife was not on board with this plan, skeptical of my ability to safely execute the procedure. And so began many weeks of being peppered with warnings, relevant articles and concerned looks. When the time came for my first bite, nerves were high. My throat itched. My heart raced. My vision blurred. I had been botulized!
Halfway through our walk to the hospital I regained my composure. Of course I had not been instantaneously struck by an incredibly rare disease that, by the way, takes at least 12 hours after consumption to manifest and does not share many symptoms with your garden variety anxiety attack. My experience had been shaped by my mindset. A decade of learning about the psychological power of expectations could not inoculate me from its effect.
Psychologists know that beliefs about how experiences should affect us can bring about the expected outcomes. Though these “placebo effects” have primarily been studied in the context of pharmaceutical interventions (e.g. patients reporting pain relief after receiving saline they believed to be an analgesic), recent research has shown their strength in a variety of domains. Tell people that their job has exercise benefits and they will lose more weight than their coworkers who had no such belief. Convince people of a correlation between athleticism and visual acuity and they will show better vision after working out . Trick people into believing they are consuming caffeine and their vigilance and cognitive functioning increases. Some evidence shows that such interventions can even mitigate the negative effects of other experiences. For example, consuming placebo caffeine alleviates the cognitive consequences of sleep deprivation.
New research from psychologists at Colorado College suggests that this might not be the only way to get over those late nights out. Beliefs about the quality of the sleep you get might be enough to ward off negative effects of sleep-deprivation on your mental acuity. Manipulating people’s perception of how well they slept could affect cognitive functioning.
To test this hypothesis, researchers first had participants report how deeply they had slept the night before. They were then randomly assigned to either an “above average” or a “below average” sleep quality condition, and hooked up to physiological equipment that they were told could measure the quality of their previous night’s sleep through particular pulse, heart rate and brain wave signatures (in fact, it could not do this). The experimenter then “calculated” participants’ sleep quality, telling them in the “below average” condition that they had spent 16.2% of their sleep in REM (below the average of 25%) and in the “above average” condition that they had spent 28.7% of their sleep in REM (above the 25% average). All participants then completed the Paced Auditory Serial Addition Test (PASAT), a test of cognitive functioning in which participants are required to quickly add numbers that are continuously presented over audiotape. Manipulating participants’ perceptions of their sleep quality influenced their cognitive functioning, regardless of how well they reported sleeping the night before. Those who believed they had slept poorly scored 44% correct on the PASAT, while those who believed they slept well scored 70% correct. These percentages are consistent with individuals’ performances in other research who had actually slept poorly or not. The effects of perceived sleep quality were comparable to the effects of actual sleep deprivation.
A follow up experiment replicated this study while also testing the generalizability of the results (to, say, verbal as opposed to aural tests). The original results held (52% correct vs. 64% on the PASAT).The degree to which this “placebo sleep” influenced other kinds of cognitive abilities, however, remained unclear.
Given the serious consequences associated with sleep deprivation important questions on this topic clearly remain, but the new findings sit within a well-validated and growing body of research on the power of expectations to shape the limits of physiological and executive functioning. Of course, a tantalizing extension of this work would be to show how you could leverage these effects into conscious control over your cognitive limits. How can we use this to our advantage? This is a difficult question. These effects depend on an individual’s belief in the treatment. Awareness of the effect undermines its strength. I doubt that I will be able to convince myself I slept deeply last night, even though my infant son woke me up at 1 and 4am. For now, I’ll just have to send this article to my wife and hope she can shape my expectations towards more productive ends next time.