A Quantitative Research Report: The Effect of Sleep Deprivation on Short-Term Memory Performance

This is a sample assignment produced by Assignment Help Center to illustrate the structure, tone, and referencing expected in an undergraduate BSc Psychology laboratory report. The dataset reported in the Results section is illustrative and was generated for teaching purposes only; it does not describe a real sample of participants. Use it as a model for your own writing, not as a source to cite.

Abstract

Adequate sleep is widely regarded as important for cognitive functioning, yet the specific impact of a single night of restricted sleep on short-term memory remains a practical concern for students and shift workers alike. This report presents an illustrative within-subjects experiment examining whether acute sleep deprivation reduces immediate free-recall performance. Thirty-two participants were tested on a 15-item word-recall task under two conditions: following a night of normal sleep (rested) and following a night of restricted sleep (deprived). It was hypothesised that recall would be poorer in the deprived condition. Using the illustrative data, participants recalled significantly fewer words when sleep-deprived (M = 9.75, SD = 2.88) than when rested (M = 11.38, SD = 2.57), t(31) = 3.81, p < .001, dz = 0.67, representing a medium-to-large effect. The findings are consistent with the wider literature indicating that sleep loss impairs attention and memory encoding. Limitations relating to the illustrative design and directions for future research are discussed.

Introduction

Memory is not a single, unitary system. The influential modal model proposed by Atkinson and Shiffrin (1968) distinguished a limited-capacity short-term store from a more durable long-term store, and Baddeley and Hitch (1974) later reframed short-term storage as an active “working memory” comprising several interacting components. Short-term or working memory is central to everyday academic tasks such as following a lecture, holding a sentence in mind while writing, or retaining a set of instructions. Its capacity is famously limited; Miller (1956) argued that people can typically hold only around seven meaningful units at once. Because this capacity is so constrained, any factor that further reduces it may have a disproportionate effect on learning and performance.

Sleep is one such factor. There is now substantial evidence that sleep supports memory, both by protecting newly encoded information and by enabling its consolidation into long-term storage (Diekelmann & Born, 2010; Walker & Stickgold, 2004). Much of this work has focused on consolidation, showing that memory for material learned before sleep is better retained after a period of sleep than after an equivalent period of wakefulness. However, sleep loss also appears to impair the encoding stage that precedes consolidation. Yoo et al. (2007) reported that a night of total sleep deprivation reduced participants’ ability to form new declarative memories and was associated with reduced hippocampal activation during encoding. Similarly, Drummond et al. (2000) found altered patterns of brain activity during verbal learning after sleep deprivation, suggesting that the encoding system does not operate normally when sleep-deprived.

The cognitive costs of sleep loss are not confined to memory. In a systematic review, Alhola and Polo-Kantola (2007) concluded that sleep deprivation reliably impairs attention and working memory, with effects on more complex functions being more variable. A meta-analysis by Lim and Dinges (2010) found that short-term sleep deprivation had its largest effects on simple attention and vigilance, with more modest but reliable effects on working memory. One interpretation is that unstable attention and reduced alertness undermine the encoding of new material, so that fewer items are successfully registered in the first place (Frenda & Fenn, 2016). For students, who frequently sacrifice sleep before assessments, the practical implication is direct: a poor night’s sleep may reduce the very capacity that revision depends upon.

Despite this converging evidence, much of the literature relies on total sleep deprivation or on complex neuroimaging paradigms that are difficult to relate to everyday study conditions. There is value in demonstrating, with a simple behavioural task, whether even partial, one-night sleep restriction is associated with measurably poorer short-term memory. The present report uses an illustrative within-subjects design to model such a demonstration.

The following hypotheses were tested:

Experimental hypothesis (H1): Participants will recall significantly fewer words in the sleep-deprived condition than in the rested condition.

Null hypothesis (H0): There will be no significant difference in the number of words recalled between the sleep-deprived and rested conditions.

A directional (one-tailed) prediction could be justified given the prior literature; however, a two-tailed test was retained to remain sensitive to any unexpected reversal, in line with conservative practice for undergraduate work.

Method

Design

A within-subjects (repeated-measures) experimental design was used. The independent variable was sleep condition, with two levels: rested (a self-reported night of at least seven hours’ sleep) and sleep-deprived (a self-reported night of no more than four hours’ sleep). The dependent variable was short-term memory performance, operationalised as the number of words correctly recalled from a 15-item list in an immediate free-recall test. A within-subjects design was chosen because it controls for stable individual differences in memory ability and increases statistical power relative to an equivalent between-subjects design. To reduce order and practice effects, the order of conditions was counterbalanced across participants, and a different but matched word list was used in each condition.

Participants

An illustrative sample of 32 undergraduate participants (aged 18–24 years) was described for this report. Participants were assumed to be healthy adults with no diagnosed sleep disorder and not taking medication known to affect sleep or cognition. In a genuine study, participants would be recruited through opportunity sampling from a university population and would provide informed consent, with the right to withdraw at any time. No real participants were tested, and no personal data were collected; the sample and all scores are illustrative.

Materials

Two matched lists of 15 common English nouns were prepared. Words were one or two syllables in length, of moderate frequency, and concrete (for example, table, river, pencil), and the two lists were matched for average word length and frequency. Each word was presented for two seconds using presentation software on a standard laptop. A response sheet was provided for written recall, along with a short pre-test questionnaire recording the number of hours slept the previous night and current subjective alertness on a 1–10 scale. In an ethically approved study, a participant information sheet, consent form, and debrief sheet would also be used.

Procedure

Participants attended two sessions scheduled at the same time of day, approximately one week apart, to hold time-of-day effects constant. Before each session, participants reported their sleep from the previous night, which determined whether the session counted as the rested or deprived condition. At the start of each memory test, participants were told they would see a list of 15 words presented one at a time and should try to remember as many as possible. The list was then presented at a rate of one word every two seconds. Immediately after the final word, participants completed a 30-second distractor task (counting backwards in threes) to clear the contents of the phonological loop and reduce recency effects, before being given two minutes to write down as many words as they could recall in any order. Recall was scored as the number of correct words reproduced, with no penalty for intrusions. Participants were fully debriefed after the second session.

Results

The data reported in this section are illustrative and were generated for teaching purposes; they do not represent real participants. The values are, however, internally consistent, so the descriptive and inferential statistics agree with one another.

Recall scores were approximately normally distributed in both conditions, and no scores fell outside the possible range of 0–15. Descriptive statistics are presented in Table 1. On average, participants recalled more words in the rested condition than in the sleep-deprived condition, and variability was broadly similar across conditions.

Table 1

Mean number of words recalled (out of 15) by condition (illustrative data, n = 32)

The mean difference between conditions was 1.63 words (SD of the differences = 2.42), indicating that participants recalled roughly one to two fewer words when sleep-deprived. Because the design was repeated-measures and the dependent variable was continuous, a paired-samples (dependent) t-test was used to test the hypotheses.

The paired-samples t-test showed that recall was significantly lower in the sleep-deprived condition than in the rested condition, t(31) = 3.81, p < .001 (two-tailed). The 95% confidence interval for the mean difference ranged from 0.76 to 2.50 words; because this interval does not include zero, it is consistent with a genuine reduction in recall. The standardised effect size was medium-to-large (Cohen’s dz = 0.67), following the conventional benchmarks of 0.2, 0.5, and 0.8 for small, medium, and large effects respectively (Cohen, 1988). The null hypothesis was therefore rejected in favour of the experimental hypothesis.

In summary, the illustrative data support the prediction that acute sleep deprivation is associated with poorer short-term memory performance, with participants recalling on average around 14% fewer words after a night of restricted sleep.

Discussion

The present report set out to examine whether a single night of restricted sleep reduces short-term memory performance on an immediate word-recall task. Using illustrative data, recall was significantly lower in the sleep-deprived condition than in the rested condition, and the effect was of medium-to-large magnitude. This pattern supports the experimental hypothesis and is consistent with the broader literature indicating that sleep loss disrupts attention and the encoding of new information (Alhola & Polo-Kantola, 2007; Lim & Dinges, 2010).

The finding fits well with an encoding-based account of sleep-related memory impairment. If, as Yoo et al. (2007) and Drummond et al. (2000) suggest, sleep deprivation reduces the efficiency of the neural systems that register new material, then fewer items should be successfully encoded during list presentation, producing lower recall regardless of any later consolidation. Unstable attention offers a complementary explanation: because sleep deprivation most reliably impairs sustained attention (Lim & Dinges, 2010), sleep-deprived participants may simply lapse more often during presentation and miss more words. In terms of the working-memory framework (Baddeley & Hitch, 1974), reduced central-executive resources under sleep loss could limit the rehearsal and organisation that support recall from a limited-capacity store. The present task cannot distinguish these mechanisms, but all point in the same direction.

Several limitations must be acknowledged, some inherent to the design and some specific to this being an illustrative exercise. First and most importantly, the data are simulated for teaching and cannot be treated as evidence about real behaviour; the results demonstrate how such a study would be reported, not what a real sample would show. Second, the operational definition of sleep deprivation relied on self-reported hours slept rather than an objective measure such as actigraphy or polysomnography, so the manipulation would be imprecise in practice and vulnerable to inaccurate reporting. Third, a within-subjects design is susceptible to order and practice effects; although counterbalancing and matched word lists were used to mitigate these, participants might approach the second session differently, and demand characteristics could arise if participants guessed the hypothesis. Fourth, the task measured immediate recall of unrelated words, which has limited ecological validity relative to the complex, meaningful material that students actually revise. Finally, the sample was small and drawn from a narrow age range, so any real findings would generalise cautiously.

Future research could address these issues in several ways. Objective sleep monitoring would strengthen the manipulation and allow sleep duration to be treated as a continuous predictor rather than a crude dichotomy, which might reveal a dose–response relationship between hours slept and recall. Employing more ecologically valid materials, such as passages of academic text or paired-associate learning, would test whether the effect extends to the kind of material students must remember. A larger and more diverse sample would improve generalisability, and adding a measure of sustained attention would allow researchers to test directly whether attentional lapses mediate the memory impairment. It would also be informative to examine whether the effect of sleep loss is larger for encoding than for retrieval by manipulating which stage occurs under sleep deprivation.

In conclusion, the illustrative results reported here reproduce a well-established pattern: short-term memory performance is poorer following restricted sleep. Although the data are simulated, the exercise reflects genuine evidence that sleep supports memory (Diekelmann & Born, 2010; Walker & Stickgold, 2004) and carries a familiar practical message for students, namely that sacrificing sleep before an assessment may undermine the memory processes that effective learning depends upon.

References

Alhola, P., & Polo-Kantola, P. (2007). Sleep deprivation: Impact on cognitive performance. Neuropsychiatric Disease and Treatment, 3(5), 553–567.

Atkinson, R. C., & Shiffrin, R. M. (1968). Human memory: A proposed system and its control processes. In K. W. Spence & J. T. Spence (Eds.), The psychology of learning and motivation (Vol. 2, pp. 89–195). Academic Press. https://doi.org/10.1016/S0079-7421(08)60422-3

Baddeley, A. D., & Hitch, G. (1974). Working memory. In G. H. Bower (Ed.), The psychology of learning and motivation (Vol. 8, pp. 47–89). Academic Press. https://doi.org/10.1016/S0079-7421(08)60452-1

Cohen, J. (1988). Statistical power analysis for the behavioral sciences (2nd ed.). Lawrence Erlbaum Associates.

Diekelmann, S., & Born, J. (2010). The memory function of sleep. Nature Reviews Neuroscience, 11(2), 114–126. https://doi.org/10.1038/nrn2762

Drummond, S. P. A., Brown, G. G., Gillin, J. C., Stricker, J. L., Wong, E. C., & Buxton, R. B. (2000). Altered brain response to verbal learning following sleep deprivation. Nature, 403(6770), 655–657. https://doi.org/10.1038/35001068

Frenda, S. J., & Fenn, K. M. (2016). Sleep less, think worse: The effect of sleep deprivation on working memory. Journal of Applied Research in Memory and Cognition, 5(4), 463–469. https://doi.org/10.1016/j.jarmac.2016.10.001

Lim, J., & Dinges, D. F. (2010). A meta-analysis of the impact of short-term sleep deprivation on cognitive variables. Psychological Bulletin, 136(3), 375–389. https://doi.org/10.1037/a0018883

Miller, G. A. (1956). The magical number seven, plus or minus two: Some limits on our capacity for processing information. Psychological Review, 63(2), 81–97. https://doi.org/10.1037/h0043158

Walker, M. P., & Stickgold, R. (2004). Sleep-dependent learning and memory consolidation. Neuron, 44(1), 121–133. https://doi.org/10.1016/j.neuron.2004.08.031

Yoo, S. S., Hu, P. T., Gujar, N., Jolesz, F. A., & Walker, M. P. (2007). A deficit in the ability to form new human memories without sleep. Nature Neuroscience, 10(3), 385–392. https://doi.org/10.1038/nn1851