The trait of Introversion-Extraversion predicts vulnerability to sleep deprivation

Research design/methodology

TYPE: A case report of a clinical psychological study with the use of randomization into groups which were given caffeine and placebo chewing gums.

VALIDITY: The report does not describe the distribution of introverts and extraverts in the study subjects. The small number of subjects (23) may have affected the results.

ENVIRONMENT: The study was conducted in a military environment.

Research question 

Do the traits of introversion and extraversion predict vulnerability to sleep deprivation?

Overnight psychomotor vigilance performance and attention lapses were measured during prolonged wakefulness of 77 hours. 

Patient/Problem/Population definition

PATIENT: Healthy military personnel with personality traits of introversion and extraversion.

PROBLEM: Individuals respond differently to prolonged wakefulness (more than the normal 16-hr period of daytime activity), with some who seem to function effectively on very little sleep. There is deficiency of understanding of the underlying psychological, motivational and neurobiological causes for these differences.

POPULATION: Healthy adult military personnel, ranging in age from 20 to 35 years, non-smokers, with low to moderate habitual caffeine users (<300 mg ⁄ day).

TYPE: Clinical psychological research

Intervention 

An episode of prolonged wakefulness was created by continuous sleep deprivation for 77 hours. Participants were also randomly assigned, in a double-blinded procedure, to receive either caffeine chewing gum preparation or an identical flavored placebo gum.

Comparison

Extraverts’ and introverts’ performance on psychological tests for simple psychomotor vigilance (i.e. speed of reaction time to a simple visual stimulus) was measured by using the Walter Reed Palm-Held Psychomotor Vigilance Test (Palm-PVT), a psychological test of reaction time administered via a hand-held PDA device. The components of the testing system include (1) the PalmPVT.prc software deployed on a PDA, (2) a Windows companion program installed on a PC, and (3) HotSync software that controls bidirectional communication between the PC and the PDA at the beginning of the test and at the end when the data needs to be transferred to the PC for analysis.  During the test, visual stimuli are presented on the liquid crystal display (LCD) of the PDA, and the subject responds by pressing a specified button on the device. The PDA device and PVT software have been previously tested in the field and compared with conventional commercial devices they have shown to be as sensitive to the study parameters while concurrently providing additional user-selectable stimulus, feedback, control, and data options. 

Outcome  

Higher baseline scores on extraversion were significantly associated with poorer Palm-PVT performance (p = 0.007), when controlling for the effects of caffeine stimulation, on the first night of the study. However, extraversion was not significantly associated with performance in night 2 or night 3 as compared to introversion. Additionally, the relationship of performance with extraversion remained statistically significant when the speed of performances were averaged across all three nights. Interestingly, caffeine administration was found to improve performance through out the study period 

Application of results to patient care

Further research to study the effects of different social learning and experience aspects on personality traits and thus on the study results need to be determined before the results can be applied to patient care. Additionally, independent tests comparing the use of the PDAs by extraverts and introverts should be done to assess the effects of personality traits on the ability to use the PDA and thus the validity of PDA-based test results. Furthermore, it should be explored if prior experience with PDAs could have affected the study results.

The study had a strict inclusion criteria and it is possible that the study results may not be generalizable to the population excluded from the study. Overall, the study population consisted of healthy young (20-35 yr olds) military personnel, and this cohort is expected to have had some experience with using electronic devices such as the PDA used in the study. The relative ease of use and familiarity with the device may have biased the results.