Question

The ability to recognize and interpret facial expressions is key to successful human interaction. Could this ability be compromised by sleep deprivation? A 2015 study \(^{58}\) took 18 healthy young adult volunteers and exposed them to 70 images of facial expressions, ranging from friendly to threatening. They were each shown images both after a full night of sleep and after sleep deprivation ( 24 hours of being awake), and whether each individual got a full night of sleep or was kept awake first was randomly determined. The study found that people were much worse at recognizing facial expressions after they had been kept awake. (a) What are the explanatory and response variables? (b) Is this an observational study or a randomized experiment? If it is a randomized experiment, is it a randomized comparative experiment or a matched pairs experiment? (c) Can we conclude that missing a night of sleep hinders the ability to recognize facial expressions? Why or why not? (d) In addition, for the people who had slept, the study found a strong positive association between quality of Rapid Eye Movement (REM) sleep and ability to recognize facial expressions. Can we conclude that better quality of REM sleep improves ability to recognize facial expressions? Why or why not?

Short answer

a) Explanatory variable: sleep quantity and quality, Response variable: ability to interpret facial expressions \n b) This is a randomized experiment, specifically a matched pairs experiment. \n c) Yes, based on this randomized experiment, we could argue there is a cause and effect relationship between sleep (or lack thereof) and ability to recognize facial expressions. \n d) While the experiment found a correlation between REM sleep and ability to recognize facial expressions, without an experiment set up specifically to test this, we cannot conclude causation.

Step-by-step solution

Identify the Explanatory and Response Variables

The explanatory variable, the one that is manipulated or changed during the experiment, is the quality and amount of sleep the participants got before being showed the images. The response variable, the one that is measured or observed, is the volunteers' ability to recognize facial expressions correctly.

Identify the Type of Experiment

This is a randomized comparative experiment, more specifically a matched pairs experiment. It is matched pairs because each individual is tested twice, once after a full night of rest and once after sleep deprivation. The order of conditions (sleep or sleep deprivation) was randomly assigned, allowing each participant to serve as their own control and minimizing the effects of lurking variables.

Draw Conclusions about Causation

Based on the experiment set up, there appears to be a cause-and-effect relationship between sleep deprivation and decreased ability to recognize facial expressions. However, as with all scientific findings, these conclusions are subject to further validation and can always be refined with additional data.

Discuss Secondary Finding

The study also found a positive association between quality of REM sleep and participants' ability to recognize facial expressions. Yet, in this case, correlation does not necessarily imply causation. This is because the study can't rule out the possibility of a lurking variable influencing this observation, without experimenting specifically on REM sleep.