Children will participate in 2 exposure conditions in their own homes (i.e., experimental and internal negative control), facilitated by research staff (one week apart, counterbalanced to control for possible order effects). The internal negative control will be the same for all groups, but the experimental exposure will differ. Both exposures will take place for 1 hour before bed in room lighting (40-50 lux).

Experimental exposure: children in Group 4 will be exposed to a tablet with filtered dim screen light and calming media content (DL/CC).

Internal negative control exposure: children will participate in non-screen-based quiet activities

Bright light screen media exposure will be delivered on an iPad Pro provided by the research team which will be set to the brightest light intensity setting for 1 hour before bed in room lighting 40-50 lux

Filtered dim light screen media exposure will be delivered for 1 hour before bed in room lighting 40-50 lux on an iPad Pro provided by the research team. A blue light filter will be used to alter the spectral distribution of the emitted light and the screen brightness will be dimmed to the lowest possible setting

We will create a 1-hour recording of movie clips containing exciting content from age-appropriate movies for 8- to 11-year-old children as rated by Common Sense Media.

We will create a 1-hour recording of movie clips containing calming content from age-appropriate movies for 8- to 11-year-old children as rated by Common Sense Media.

Children will wear an Actiwatch Spectrum watch (Philips Respironics, Inc.) on the wrist of their non-dominant hand. Sleep latency (i.e., the time between when they child starts to try to fall asleep as indicated by a push of the event marker button on the Actiwatch and when the child falls asleep (first 3 consecutive epochs of sleep).

Heart rate (HR) will be assessed using a Polar H10 HR monitor which integrates with the Actigraph GT3X-BT devices to record HR data from which raw data can be extracted. The Polar H10 HR monitor will be worn on a chest strap fitted to the child according to manufacturer guidelines during the 1-hour experimental and internal negative exposures.

Heart rate variability (HRV) will be assessed using a Polar H10 HR monitor which integrates with the Actigraph GT3X-BT devices to record HR data from which raw data can be extracted. The Polar H10 HR monitor will be worn on a chest strap fitted to the child according to manufacturer guidelines during the 1-hour experimental and internal negative exposures.

the Pre-Sleep Arousal Scale for Children (PSAS-C) will be used to assess Children's subjective report of arousal prior to sleep on Night 2. The PSAS-C contains 16 items comprising 2 subscales assessing somatic and cognitive arousal and demonstrated high internal consistency. Items are scored on a Likert scale from 1 to 5 with scores ranging from 16 to 80. Higher scores indicate greater pre-sleep arousal.

The Pictorial Sleepiness Scale is a measure of perceived sleepiness in a given moment that has been validated with individuals 4- to 73-years of age, demonstrating a strong correlation with the Karolinska Sleepiness Scale (r=.72) and the Sandford Sleepiness Scale(r=.94). The use of cartoon faces facilitates the assessment of sleepiness in population with minimal literacy skills. Almost all participants (99%) correctly ranked the faces in order of sleepiness. Children will complete the sleepiness scale before the start of the experimental condition (~60 minute prior to bedtime), 30 minutes later, and again at bedtime.

To assess objective emotion regulation in the home on Day 3, we will use a modified version the Trier Social Stress Test (TSST), The task will begin with a 5-min baseline segment, during which children will be asked to relax while they listen to a recording of nature sounds (i.e., waves at the beach) in order to collect resting HR and HRV). After this baseline period, children will then engage in a task in which they To assess objective emotion regulation in the home on Day 3, we will use a modified version the Trier Social Stress Test (TSST), The task will begin with a 5- min baseline segment, during which children will be asked to relax while they listen to a recording of nature sounds (i.e., waves at the beach) in order to collect resting HR and HRV). After this baseline period, children will then engage in a task in which they imagine they are giving a speech in front of a class of 20 kids they have never met. Resting and task-based HR and HRV data will be collected.

Subjective reports of emotional arousal and regulation will also be collected before and after the 5-minute speech task. Children will provide ratings of arousal using the Self-Assessment Manikin (SAM), a widely-used non-verbal pictorial scale that measures arousal associated with a person's affective reaction to a wide variety of situations and stimuli. Emotion regulation will be assessed via a likert-type rating requiring children to indicate how difficult it was to regulate (control) their emotions during the speech task, from ) (not hard at all) to 10 (very hard).

Letter-number sequencing Test (WISC-V) asks children to listen to lists of letters and digits and repeat the letters back in alphabetical order, and the digits in ascending numerical order, with the lists increasing in length from 2-8 alphanumeric characters throughout the test. Children will be read three different alphanumeric series for each list lengths, and one point will be awarded for each correct recall, for a total of 21 points. This performance score will be used as a measure of working memory.

The Color-Word Interference Test (D-KEFS) is a standard "Stroop-like" task. Across the two tasks, inhibition and inhibition switching, completion time and errors (4 indicators in total) are used as markers of inhibitory control. The inhibition task is a standard "Stroop-like" task. During inhibition switching, participants also encounter words in colored ink wherein they say the color and inhibit reading the work. However, during some trials, words are enclosed by a box wherein the participant needs to switch to reading, not naming, the color in which it is printed.

Assesses vigilant attention (reaction time to changes in visual stimuli) and is sensitive to changes in sleep.

To assess for other types of screen use without over burdening parents with screen use diaries that require reporting of screen use in 15-minute increments 24 hours a day, we will add brief questions to the daily sleep diary regarding how much time (hours and minutes) the child spent on other screen devices each day (computer, video games, time spent on siblings or parent's mobile devices, t.v., etc.).

Information will be obtained at baseline including child sex at birth and gender, parent sex and gender, parent education, family income, and child race and ethnicity. Family income-to-needs ratio will be calculated.

Structured interviews with children and parents will be conducted during screening over Zoom for the convenience of families. We will use the Mini International Neuropsychiatric Interview for Children and Adolescents (MINI-KID) or the Kiddie Schedule for Affective Disorders and Schizophrenia (K-SADS), a short structured diagnostic interview for assessing psychiatric disorders in children and adolescents. To assess for possible sleep disorders, we will conduct a brief interview with children and parents derived from the reliable B.E.A.R.S. algorithm will be used to screen for sleep problems and disorders (i.e., bed time/sleep onset problems, excessive daytime sleepiness, awakenings from sleep, regularity/duration of sleep, and snoring). Positive screens will be followed by full evaluation using diagnostic criteria for suspected sleep disorders.

The Pubertal Development Scale (PDS) is a parent report measure consisting of five questions about pubertal status, with five answer categories (1= has not yet started changing, 2 = has barely started changing, 3 = changes are definitely underway, 4 = changes seem complete, and 0 = I do not know). A continuous PDS score is converted to a 5-point ordinal scale (in keeping with the original Tanner categories) using an algorithm described by Carskadon and Acebo. The PDS evidences high rates of test-retest reliability and agreement with clinician-performed Tanner staging.

Will be assessed by the Bedtime Routines Questoinnaire. The Bedtimes Routines Questionnaire (BRQ), is a 31-item parent report measure of children's bedtime routines, comprised of three scales measuring consistency of bedtime routines (weekday & weekend), reactivity to changes in bedtime routines, and frequency of adaptive and maladaptive activities. The BRQ scales had good internal consistency ranging from α = 0.69 to 0.90. Additionally, the measure has been validated in a community sample of primary caregivers of children ages 2 to 8 years old and has been used to measure bedtime routines with children ages 6 to 12 years old.

Chronotype refers to one's physiological preference for morningness or eveningness relative to social timing. Chronotype will be assessed during the run-in period based on parent report using the Children's Chronotype Questionnaire (CCTQ) which provides 3 measures of chronotype: 1) the midpoint of sleep on free days, 2) the morningness/Eveningness scale score, and a 5-point Chronotype score using a RedCap survey. This questionnaire has demonstrated evidence of validity to assess Chronotype among 4-11 year-olds.

Children will wear an Actiwatch Spectrum watch (Philips Respironics, Inc.) on the wrist of their dominant hand 24-hours a day to assess sleep patterns throughout the study. This will be used to ensure that participants adhere to the bedtimes and waketimes recommended in the study protocol. Actigraphy is a reliable method for determining sleep-wake patterns in children. The Actiwatch Spectrum is a lightweight watch that collects continuous movement data in 1-minute epochs via a highly sensitive piezo-electric accelerometer. Children (with reminders from caregivers) press a button on the watch each day when they get into bed and when they get out of bed (i.e., event markers) to provide a reliable estimation of the nighttime sleep period. The watch also has an off-wrist sensor which beeps to remind the child to put on the watch when taken off. The validated Sadeh algorithm will be used to derive the bed time and wake time to examine adherence to the sleep schedule.