AP Psychology EBQ Practice

How does sleep deprivation differentially affect cognitive performance on tasks of varying complexity? This study examines the relationship between sleep loss and task performance through the lens of arousal theory, which suggests that optimal performance depends on matching arousal levels to task demands—with simple tasks requiring higher arousal and complex tasks benefiting from moderate arousal levels.

This between-subjects experiment was conducted in a controlled laboratory setting equipped with individual testing stations. Researchers randomly assigned participants to either the sleep deprivation condition or the control condition to examine how acute sleep loss affects performance on cognitive tasks of differing complexity.

All participants arrived at the laboratory at 8:00 AM for testing. Sleep-deprived participants had been monitored since 8:00 AM the previous day, while control participants arrived after a normal night's sleep. Following informed consent and a brief orientation, participants completed both cognitive tasks in counterbalanced order with a 10-minute break between tasks. The entire testing session lasted approximately 45 minutes.

The Psychomotor Vigilance Task (PVT) served as the simple task measure, requiring participants to press a button as quickly as possible when a visual stimulus appeared at random intervals over a 10-minute period. Performance was operationalized as mean reaction time in milliseconds. The Logical Reasoning Test (LRT) served as the complex task measure, consisting of 30 syllogism problems requiring deductive reasoning, with participants given 20 minutes to complete as many items as possible. Performance was operationalized as the percentage of items answered correctly.

Sleep Deprived (24 hours awake): Participants remained awake in a monitored sleep laboratory for 24 continuous hours prior to testing. Research assistants supervised participants throughout the night, engaging them in low-stimulation activities such as reading, watching documentaries, or playing card games. Caffeine and other stimulants were prohibited.

Control (Normal sleep): Participants maintained their regular sleep schedules the night before testing and were required to sleep at least 7 hours, verified through sleep diary entries and actigraphy wristbands.

Independent samples t-tests were conducted for each task. Cohen's d effect sizes indicated a large effect for the PVT (d = 2.28) and a small, non-significant effect for the LRT (d = 0.21). Alpha was set at .05 for all analyses.

These findings support arousal theory's predictions regarding the interaction between arousal levels and task complexity. Sleep deprivation, which reduces arousal, severely impaired performance on the simple vigilance task that requires sustained attention and higher arousal, while leaving complex reasoning relatively intact—possibly because lower arousal levels may actually approach the moderate optimal level needed for complex cognitive processing.

Brennan, K. L., Okonkwo, D. M., & Harrington, S. J. (2021). Differential effects of acute sleep deprivation on simple and complex cognitive task performance: Support for arousal theory. Journal of Experimental Psychology: Applied, 27(3), 418-432.

How does chronic partial sleep restriction accumulate over time to affect cognitive performance? This experimental study examined the concept of sleep debt by investigating whether consecutive nights of reduced sleep produce cumulative cognitive deficits that compound over time, even when individuals do not perceive significant impairment.

This controlled laboratory experiment was conducted in a sleep research facility where participants resided for 16 consecutive days (2 baseline days plus 14 experimental days). The facility controlled for light exposure, caffeine, alcohol, and napping opportunities to isolate the effects of sleep restriction.

After two baseline nights of 8-hour sleep opportunities, participants were randomly assigned to one of three sleep conditions for 14 consecutive nights. Each day at 10:00 AM, 2:00 PM, and 6:00 PM, participants completed a 10-minute Psychomotor Vigilance Task (PVT) and a subjective sleepiness rating. Polysomnography confirmed actual sleep duration each night.

Cognitive performance was measured using lapses on the PVT, operationally defined as reaction times exceeding 500 milliseconds. The daily lapse score was calculated as the average number of lapses across the three testing sessions. Subjective sleepiness was assessed using the Stanford Sleepiness Scale (1 = fully alert to 7 = almost asleep).

8-hour condition: Participants were given 8 hours in bed each night (11:00 PM - 7:00 AM), serving as the control condition

6-hour condition: Participants were restricted to 6 hours in bed each night (1:00 AM - 7:00 AM), representing moderate sleep restriction

4-hour condition: Participants were restricted to 4 hours in bed each night (3:00 AM - 7:00 AM), representing severe sleep restriction

A mixed-design ANOVA revealed a significant interaction between sleep condition and day, F(26, 585) = 14.72, p < .001, η²p = .40. Post-hoc comparisons confirmed that both the 4-hour and 6-hour conditions differed significantly from the 8-hour condition by Day 3 (p < .01) and continued to diverge thereafter.

These findings demonstrate that sleep debt accumulates in a dose-dependent manner, with cognitive impairment building steadily even when individuals perceive themselves as only mildly sleepy. The dissociation between objective performance deficits and subjective awareness of impairment has critical implications for understanding why sleep-deprived individuals often fail to recognize their compromised cognitive state.

Morrison, K. L., Tanaka, R., & Blackwood, S. E. (2021). Chronic sleep restriction and the accumulation of neurocognitive deficits: A controlled laboratory study. Sleep Medicine Reviews, 58(3), 234-251.

What role do specific sleep stages play in the consolidation of procedural memory? This experiment investigated whether REM sleep, compared to slow-wave sleep (SWS), is differentially important for strengthening newly acquired motor and perceptual skills, addressing fundamental questions about sleep-dependent memory consolidation mechanisms.

Participants spent two consecutive nights in a sleep laboratory equipped with polysomnography (PSG) monitoring systems to track sleep stages via EEG, EOG, and EMG recordings. Each participant was randomly assigned to one of three experimental conditions involving targeted sleep stage disruption.

On the first evening, all participants completed training on a visual texture discrimination task, which required identifying the orientation of a target array embedded in a background of horizontal lines presented briefly (16 ms) before a mask. Baseline performance thresholds were established as the minimum stimulus-to-mask interval (SOA) at which participants achieved 80% accuracy. Participants then slept overnight in the laboratory while undergoing their assigned sleep manipulation. The following morning, after a standardized wake period of 90 minutes, participants completed the texture discrimination task again under identical conditions.

The dependent variable was improvement in visual texture discrimination, operationally defined as the decrease in stimulus-to-mask onset asynchrony (SOA in milliseconds) needed to maintain 80% accuracy from pre-sleep baseline to post-sleep testing. Greater decreases indicated stronger procedural memory consolidation.

REM Deprived: Participants were awakened by a tone each time PSG indicated entry into REM sleep and kept awake for 3 minutes before being allowed to return to sleep (n = 21)

SWS Deprived: Participants were awakened each time PSG indicated entry into slow-wave (N3) sleep and kept awake for 3 minutes before being allowed to return to sleep (n = 21)

Control: Participants were awakened an equivalent number of times during Stage N2 (light sleep) to control for disruption effects without targeting memory-critical stages (n = 21)

Post-hoc Tukey HSD tests confirmed that the REM Deprived group improved significantly less than both the SWS Deprived group (p < .001) and the Control group (p < .001), while SWS Deprived and Control groups did not differ significantly from each other (p = .89).

These findings demonstrate that REM sleep plays a critical and selective role in procedural memory consolidation, as only disruption of REM sleep—not slow-wave sleep—prevented overnight improvement on the perceptual skill task. This supports the hypothesis that REM sleep provides unique neurobiological conditions, potentially involving acetylcholine-mediated plasticity, necessary for stabilizing procedural memories.

Nakamura, T., Westbrook, R. F., & Chen, L. M. (2021). Selective REM sleep deprivation impairs consolidation of visual procedural learning in young adults. Journal of Sleep Research, 30(4), 287-298.