Taking an intervening test between learning episodes can enhance later source recollection. Paradoxically, testing can also increase people's susceptibility to the misinformation effect -a finding termed retrievalenhanced suggestibility (RES, Chan, Thomas, & Bulevich, 2009). We conducted three experiments to examine this apparent contradiction. Experiment 1 extended the RES effect to a new set of materials. Experiments 2 and 3 showed that testing can produce opposite effects on memory suggestibility depending on the complexity of the source test. Specifically, retrieval facilitated source discriminations when the test contained only items with unique source origins. But when the source test included some items that had appeared in multiple sources, the intervening test actually increased source confusions. These results have implications for a wide variety of learning situations. We focused our discussion on eyewitness memory, source complexity, and reconsolidation. Taking an intervening test between learning episodes can enhance later source recollection.

Across all ages, individuals with Down syndrome (DS) experience high rates of sleep problems as well as cognitive impairments. This study sought to investigate whether circadian rhythm disruption was also experienced by people with DS and whether this kind of sleep disorder may be correlated with cognitive performance. A cross-sectional study of 101 participants (58 with DS, 43 with typical development) included individuals in middle childhood (6–10 years old), adolescence (11–18 years old), and young adulthood (19–26 years old). Sleep and markers of circadian timing and robustness were calculated using actigraphy. Cognitive and behavioral data were gathered via a novel touchscreen battery (A-MAPTM, Arizona Memory Assessment for Preschoolers and Special Populations) and parent questionnaire. Results indicated that children and adolescents with DS slept the same amount as peers with typical development, but significant group differences were seen in phase timing. The circadian robustness markers, interdaily stability and intradaily variability of sleep-wake rhythms, were healthiest for children regardless of diagnostic group and worst for adults with DS. Amplitude of the 24-h activity profile was elevated for all individuals with DS. In analyses of the correlations between sleep quality, rhythms, and cognition in people with DS, interdaily stability was positively correlated with reaction time and negatively correlated with verbal and scene recall, a finding that indicates increased stability may paradoxically correlate with poorer cognitive outcomes. Further, we found no relations with sleep efficiency previously found in preschool and adult samples. Therefore, the current findings suggest that a thorough examination of sleep disorders in DS must take into account age as well as circadian robustness to better understand sleep-cognitive correlations in this group.

Lynn Nadel has been a trailblazer in memory research for decades. In just one example, Nadel and Zola‐Morgan [Infantile amnesia, In Infant memory, Springer, Boston, MA, 1984, pp. 145–172] were the first to present the provocative notion that the extended development of the hippocampus may underlie the period of infantile amnesia. In this special issue of Hippocampus to honor Lynn Nadel, we review some of his major contributions to the field of memory development, with an emphasis on his observations that behavioral memory assessments follow an uneven, yet protracted developmental course. We present data emphasizing this point from memory‐related eye movements [Hannula & Ranganath, Neuron, 2009, 63(5), 592–599]. Eye tracking is a sensitive behavioral measure, allowing for an indication of memory function even without overt responses, which is seemingly ideal for the investigation of memory in early childhood or in other nonverbal populations. However, the behavioral manifestation of these eye movements follows a U‐shaped trajectory—and one that must be understood before these indictors could be broadly used as a marker of memory. We examine the change in preferential looking time to target stimuli in school‐aged children and adults, and compare these eye movement responses to explicit recall measures. Our findings indicate change in the nature and timing of these eye movements in older children, causing us to question how 6‐month‐old infants may produce eye movements that initially appear to have the same properties as those measured in adulthood. We discuss these findings in the context of our current understanding of memory development, particularly the period of infantile amnesia.

Sleep quality is increasingly recognized as a potential factor influencing healthy cognitive and neural development across the lifespan. It is becoming more recognized as an important factor for persons with Down syndrome, and this chapter describes the most recent literature regarding sleep disturbance, its correlates, and findings from animal models in this population. The authors discuss the relation of poor sleep to behavioral, brain, and cognitive dysfunction and highlight the family consequences for altered sleep in children with Down syndrome. These pervasive sleep deficits have the potential to derail cognitive development during critical periods for language learning and could also exacerbate age-related cognitive decline. The authors hope that this compilation of evidence regarding sleep deficits in persons with Down syndrome will help facilitate more treatment studies for sleep disorders in this population, including treatments aimed at poor sleep in infants, as well as mid-adulthood, which may lessen or delay the impact of the pathological progression of Alzheimer’s disease. Methodological challenges to sleep research are discussed, and future directions for this field are highlighted.