Seasonal variation in pigeon body weight and delayed matching-to-sample performance

The weights of 5 pigeons with free access to food, monitored over 3 calendar years in the laboratory, were found to fluctuate with season. All pigeons were at their heaviest in the winter and were lightest in the summer. Five different pigeons performed a standard delayed matching-to-sample task for 44 weeks from January to November. Their weights were held at 85% of their summer free-feeding weights, making their predicted deprivation level higher in the winter relative to predicted winter free-feeding weights. Slopes of forgetting functions fit to weekly response totals for each pigeon were shallower in winter, showing an improvement in accuracy with longer delays. Thus, delayed matching-to-sample performance may have been affected by the practice of maintaining the pigeons at a constant body weight throughout the calendar year.     

Inducing lucid dreams by olfactory-cued reactivation of reality testing during early-morning sleep: A proof of concept

The reliable induction of lucid dreams is a challenge in lucid dream research. In a previous study by our research group we were able to induce in about 50% of the participants a lucid dream in a single sleep laboratory night by combining a wake-up-back-to-bed sleep protocol and a mnemonic technique. In the present study, we extended our previous procedure by additional presentation of an odor during sleep to reactivate memory traces about reality testing. In total 16 male participants spent a single night in the sleep lab whereas the procedure induced in two participants a lucid dream (12.5%). The induction rate stays below the success rate of our previous study and therefore odor-cueing seems not a promising technique for inducing lucid dreams. Beside the odor presentation, several other methodological changes have been made, which will be discussed and hopefully help further dream engineering to improve induction techniques.     

Sleep fragmentation and lucid dreaming

Lucid dreaming—the phenomenon of experiencing waking levels of self-reflection within one’s dreams—is associated with more wake-like levels of neural activation in prefrontal brain regions. In addition, alternating periods of wakefulness and sleep might increase the likelihood of experiencing a lucid dream. Here we investigate the association between sleep fragmentation and lucid dreaming, with a multi-centre study encompassing four different investigations into subjective and objective measures of sleep fragmentation, nocturnal awakenings, sleep quality and polyphasic sleep schedules. Results across these four studies provide a more nuanced picture into the purported connection between sleep fragmentation and lucid dreaming: While self-assessed numbers of awakenings, polyphasic sleep and physiologically validated wake-REM sleep transitions were associated with lucid dreaming, neither self-assessed sleep quality, nor physiologically validated numbers of awakenings were. We discuss these results, and their underlying neural mechanisms, within the general question of whether sleep fragmentation and lucid dreaming share a causal link.     

Three consecutive nights of sleep loss: Effects of morning caffeine consumption on subjective sleepiness/alertness,reaction time and simulated driving performance

Caffeinated products are often consumed as a popular countermeasure to the effects of sleep loss. However, the efficacy of caffeine to exert these effects after consecutive nights of sleep loss is poorly understood. The aim of this study was to investigate the effects of three consecutive nights of restricted sleep and morning caffeine consumption on subjective ratings of sleepiness/alertness, reaction time, and simulated driving performance. Twenty healthy, habitual caffeine consumers (11 females; age: 23.3 ± 5.7 y; BMI: 22.3 ± 3.5 kg⋅m⁻²; caffeine intake: 204 ± 89 mg⋅day⁻¹; Mean ± SD) who had normal sleeping patterns (≥8 h⋅night⁻¹) participated in this double-blind, placebo-controlled, randomised study. Following one night of normal sleep (≥8 h time in bed (TIB)), participants underwent three consecutive nights of restricted sleep (5 h TIB). Participants received caffeine (200 mg; n = 10) or placebo (n = 10) capsules each morning and all participants received caffeine (100 mg) capsules each afternoon. Subjective ratings of alertness, concentration and tiredness were measured before and 1 h after morning capsule administration. Choice Reaction Time (CRT) was examined 1 h after morning capsule administration, with response speed and accuracy as outcome variables. Driving performance was assessed using a 30 min simulated driving task, with lateral (standard deviation of lane position [SDLP]; total number of line crossings [LC]) and longitudinal (standard deviation of speed [SDSP]) measures of vehicle control as outcome variables. Alertness and concentration significantly decreased, and tiredness increased across the three days of sleep loss. Caffeine only marginally alleviated these effects. No differences were observed between treatments or across trial days for response speed and accuracy on the CRT task. Likewise, no significant differences were observed between groups or across trial days for any measures of simulated driving performance. Overall, results from this study indicate that three consecutive days of sleep loss influence subjective ratings of alertness, concentration and tiredness, but does not alter CRT or simulated driving performance. Caffeine may alleviate some of the negative subjective effects imposed by restricted sleep, but the efficacy of caffeine to attenuate performance changes in CRT and driving performance were unable to be observed.     

Sleep-competing behaviours among Australian school-attending youth: Associations with sleep,mental health and daytime functioning

Sleep problems are highly prevalent among school-attending youth, and impact on school performance and outcomes. Sleep-competing behaviours are likely factors in the inadequate sleep time and related functional outcomes observed in this population. We examined a range of sleep-competing behaviours and their associations with sleep variables in Australian school-attending youth. We also assessed whether these behaviours indirectly affected mental health and daytime functioning through poorer sleep quality. A total of 353 school-attending youth (mean age = 14.6 years, 53% female) were recruited from high schools in Australia, and completed a range of self-report measures. Approximately 50% of the youth obtained sub-optimal levels of sleep and reported having a problematically long sleep onset latency. Sleep competing behaviours, related and unrelated to electronic media use, were reported as occurring frequently, and were associated with a range of sleep variables. These behaviours were also related to poorer mental health and daytime sleepiness, with this association explained by indirect effects through sleep quality. Sleep-competing behaviours are prevalent on school nights in Australian youth, and may have adverse associations with mental health and functioning. Prevention and intervention programs might address the risk factors identified in the current study.     

Effect of external motion on correspondence between infant actigraphy and maternal diary

Correspondence between infant actigraphy and mother-recorded diary differed significantly when receiver–operator function area under the curve, correlation, and logistic regression was calculated with and without excluding periods of external motion. External motion occurred in 40% of recording time and significantly changed activity count per epoch.     

Family influences on the association between sleep problems and anxiety in a large sample of pre-school aged twins

Research suggests that environmental influences are important on the association between sleep problems and anxiety in children. This study examines family influences on the association between sleep problems and anxiety in 6000+ twin pairs. Parents provided information on their twins’ anxiety and sleep problems at ages 3 and 4 years. The family influences maternal depression, life events, socio-economic status, family illness, and family disorganization, were examined using parent-report. Family disorganization and maternal depression showed the strongest correlations with sleep problems (r = .20, .21, respectively) and with anxiety (r = .24, .28). Subsequent analyses indicated that family disorganization and maternal depression (examined individually) each accounted for approximately 30% of the association between sleep problems and anxiety (r = .18). The remaining association was mainly explained by environmental factors making children in the same family alike and genetic influences. This study specifies family influences that may be important in the association between sleep problems and anxiety and highlights areas of research that may be worth pursuing in order to further understand the childhood association between sleep problems and anxiety.     

Contingent employment in academic careers: Relative deprivation among adjunct faculty

This article utilizes relative deprivation theory to examine the careers of non-tenure-track instructors and research associates. Demographic status, motivations for accepting contingent employment, and standards of comparison used to assess the quality of the job were all related to the degree of relative deprivation experienced by adjunct faculty. Furthermore, even after controlling for the level of objective job rewards (e.g., salary) and objective working conditions (e.g., hours worked), relative deprivation was consistently and negatively related to both career attitudes and job behaviors. The article concludes with directions for future theory development, empirical research, and management practice in regard to academics and other highly-skilled professionals engaged in contingent employment.     

跨情境下集群行为的动因机制

群体性事件是当下我国典型的集群行为。本研究通过实验室情景设计的方法, 考察了跨情境下群体相对剥夺如何通过群体认同作用于集群行为, 及群体愤怒和群体效能对集群行为的影响。结果表明：1) 同一触发情境下, 群体认同调节群体相对剥夺－集群行为(意向)之间的关系。一般群体认同凸显的个体在高群体相对剥夺水平下有更强烈的集群行为参与(意向)。这源自群体认同对群体相对剥夺不同水平下群体效能与集群行为意向之间的二次调节。对于特定群体认同凸显的个体, 无论群体相对剥夺水平的高低, 都有较高的集群行为参与(意向)。这当中, 群体愤怒起到了部分中介的作用。2) 不同触发情境下, 群体认同对群体相对剥夺与集群行为意向的调节作用出现差异。该调节作用仅出现在利益无关情境中。此外, 群体愤怒与群体效能对集群行为意向的影响在不同情境下有区别：在利益无关情境中, 群体愤怒的影响显著大于群体效能; 在利益相关情境中, 群体效能与群体愤怒的影响无显著差异。本研究扩展了集群行为的双路径模型, 并为政府预防和化解群体性事件提供思路。     

Sleep disruption explains age-related prospective memory deficits: implications for cognitive aging and intervention

The high prevalence of sleep disruption among older adults may have implications for cognitive aging, particularly for higher-order aspects of cognition. One domain where sleep disruption may contribute to age-related deficits is prospective memory—the ability to remember to perform deferred actions at the appropriate time in the future. Community-dwelling older adults (55–93 years, N = 133) undertook assessment of sleep using actigraphy and participated in a laboratory-based prospective memory task. After controlling for education, sleep disruption (longer awakenings) was associated with poorer prospective memory. Additionally, longer awakenings mediated the relationship between older age and poorer prospective memory. Other metrics of sleep disruption, including sleep efficiency and wake after sleep onset, were not related to prospective memory, suggesting that examining the features of individual wake episodes rather than total wake time may help clarify relationships between sleep and cognition. The mediating role of awakening length was partially a function of greater depression and poorer executive function (shifting) but not retrospective memory. This study is among the first to examine the association between objectively measured sleep and prospective memory in older adults. Furthermore, this study is novel in suggesting sleep disruption might contribute to age-related prospective memory deficits; perhaps, with implications for cognitive aging more broadly. Our results suggest that there may be opportunities to prevent prospective memory decline by treating sleep problems.