Question

It is well-known that lack of sleep impairs concentration and alertness, and this might be due partly to late night food consumption. A 2015 study \(^{54}\) took 44 people aged 21 to 50 and gave them unlimited access to food and drink during the day, but allowed them only 4 hours of sleep per night for three consecutive nights. On the fourth night, all participants again had to stay up until 4 am, but this time participants were randomized into two groups; one group was only given access to water from \(10 \mathrm{pm}\) until their bedtime at \(4 \mathrm{am}\) while the other group still had unlimited access to food and drink for all hours. The group forced to fast from \(10 \mathrm{pm}\) on performed significantly better on tests of reaction time and had fewer attention lapses than the group with access to late night food. (a) What are the explanatory and response variables? (b) Is this an observational study or a randomized experiment? (c) Can we conclude that eating late at night worsens some of the typical effects of sleep deprivation (reaction time and attention lapses)?

Short answer

(a) The explanatory variable is the late-night food intake (water-only or unlimited food and drink). The response variables are the performance in tests of reaction time and the number of attention lapses. \n(b) This is a randomized experiment because participants were assigned to groups by the experimenter. \n(c) The experiment suggests that eating late at night may exacerbate the effects of sleep deprivation, but further research is needed to solidify this conclusion.

Step-by-step solution

Identify the Explanatory and Response Variables

The Explanatory variable (independent variable) is the late-night intake of food and drink, which includes two groups: one with water-only access after 10 pm and another with unlimited access to food and drink. The response variables (dependent variables) are performance in tests of reaction time and the number of attention lapses.

Identify the Type of Study

This is a randomized experiment. The participants were randomly assigned into two groups, and they did not choose which group to belong to themselves. This factor helps to reduce the impact of confounding variables and allows us to establish cause-and-effect relationships.

Evaluate the Conclusion

From the experiment, a conclusion can be drawn that late-night eating and drinking might worsen some of the typical effects of sleep deprivation such as longer reaction time and more attention lapses. However, although the experiment results in a significant difference, other confounding factors may exist, which might impact the results. Therefore, we should state that further research is needed to solidify the conclusion.