Scullin Krueger Ballard 2018

Following PSG biocalibrations, participants were instructed that they could fall asleep (lights out) at approximately 2230 hours.

PSG stands for Polysomnography, “somno” must come from the latin for “sleep”, and the greek “graphy” meaning “to write”. The prefix “poly” in polysomnography must refer to the different recording methods described under the “Overnight Polysomnography (PSG)” section on the paper: electroencephalography from 13 channels, electrooculography, and mentalis electromyography. Biocalibrations here must refer to the process of turning disparate brain activity sampled from many electrodes placed on different parts of the brain into something that is machine or expert interpretable at minimum as sleep contrasted to wakefulness. The participants were told they can start to fall asleep, and the lights that interfere with the experiment were turned off. The participants were recorded using a low-illumination, infrared video system throughout the night. The specific time was picked because at midnight the “drive to sleep is already very high” and would affect results. The most interesting reason why this time was picked, is that this hour was “congruent with most laboratory polysomnography studies on college students” which can be inferred as a firmer intention towards expanding the literature and possibility of easy aggregation and comparison by a review paper just through the choice of bedtime. Lastly it isn’t obvious on the phrase but it vaguely points to the fact the expirment is only measuring sleep for a single night.

Moreover, most studies on sleep & writing have measured sleep onset latency using self-report. Here we employ polysomnography.

The comparison made between polysomnography (PSG) and self-report, points to PSG being an advancement in the objectivity of the results. This is later reinforced by the paper’s referal to PSG as the “gold standard for measuring sleep onset latency”. Self-report is a valid way to measure sleep onset latency, but there is necessarily a delay from when the event happens, and the response is recorded (when one wakes up and records it). Self-reporting also will not give an exact number of when someone fell asleep, whereas this research can, by relying on a body of work (somnography) that precisely signals the physiological signs of sleep.

Participants who wrote a To-Do List fell asleep significantly more quickly than those who wrote a Completed List, t(55) = 2.32, p = 0.02, d = .63. Figure 1 demonstrates that sleep onset latency was further reduced in participants who wrote more specific lists.

Sleep onset latency is the time elapsed before indicators of sleep were observed. To-Do lists are lists of future activities that need to be engaged in the “next few days”. Completed lists are lists of events completed in the “previous few days”. The “more specific lists” mentioned on the second sentence refers to To-Do lists with more items written down.

Altogether, what’s being described is that writing lists of future activities before bed, allows people to fall asleep more quickly than if they write about the tasks they completed in the previous few days. It also further adds that the longer the lists (and presumably the more specific), the faster people fell asleep.

The values t(55) = 2.32, p = 0.02, d= .63 are meant as a way to signal to the reader that the results were statistically significant, which is a calculation expected when making claims about the results.

There is some precedent to the idea that to-do list specificity might be beneficial. For example, one study had first-time pregnant women simulate how future labor would go, and women who showed very specific future simulations showed less worry (Brown et al., 2002). Furthermore, a study in healthy adults found that having participants imagine worrisome future events in a specific/detailed manner decreased anxiety about those events (Jing et al., 2016; see also Jansson-Fröjmark, Lind, & Sunnhed, 2012).

They are implying that the more specific the list, the more one is engaging oneself with the specifics of how the future will go, which allows one to worry less (and be able to sleep), which is similar to the decrease in worry/anxiety seen in previous studies of first-time pregnant women watching simulations of labor or healthy adults imagining future events. The names and dates in parentheses are references for the claims made, which can be found at the end of the paper for further reading and verification.

Doing the experiment for a few nights will further highlight its usefulness while being able to argue the lab setting affects the results a bit less if the participants spend a few nights in it.

I do not understand statistic significance as much as I would like. Additionally, the data talked briefly about about number of times one wakes up in the night, and seeing double digits as the average made me wonder about how the brain activity is interpretted as sleep or wakefulness.