Light is the strongest environmental signal to the internal biological clock of humans. Although the biological response to light has been investigated in adults, very little is known about how light influences the biological clock of young children. The primary goal of this study is to understand how light can delay the timing of the biological clock of preschool-age children.

Who should get involved?
We are interested in healthy children with no sleep problems who will be ages 3.0 to 5.9 years between May 2023 and August 2023.

How can my child qualify for the study?
In a brief telephone interview, we ask you questions about your child’s sleep and developmental/health history, family schedules, and parental health history. We also ask you to complete questionnaires that help us determine if your child fits into the study. If your child is eligible, we will visit you in your home for an orientation session.

How long will the study last?
The study takes place over ~3 weeks, consisting of 2 identical 10-day protocols. Both protocols can be scheduled whenever is most convenient for you between May 2023 and August 2023.

Training visits: We make brief visits to your home during the first week of the study to slowly introduce the procedures used to measure melatonin in saliva.

Sleep Schedules: Your child is given a strict bedtime and rise time schedule, which includes daytime naps (if your child is still napping) and nighttime sleep periods. Your child will follow this sleep schedule for the first 7 days of each 10-day study protocol. Following this sleep schedule is a very important part of the study.

Activity Monitoring: Your child wears a small watch-like wrist monitor throughout each 10-day protocol. This monitor records movement and lets us keep track of your child’s sleep patterns throughout the study.

Sleep Diary: You are asked to complete a brief sleep diary and telephone the lab each day to report your child’s bedtimes and rise times.

Melatonin Assessments: During the last 3 days of each study protocol, we will make your home a dim-light environment.  We do this by covering windows with black plastic and using low-wattage bulbs.  On two evenings, your child gives saliva samples by “mouthing” a dry cotton roll for about 1-minute. Saliva samples allow us to measure levels of melatonin, a hormone related to the body’s biological “clock.”  We will also get saliva samples on another day when your child is exposed to light in the evening.

Compensation: Because this study requires time and effort, your family will receive $580 cash at the end of the study and a $200 U.S. Savings Bond ($100 initial investment). Your child is also frequently rewarded with small “gifts.”

Thinking your child will never do these things? Think again! Our research team is experienced in working with young children and making study activities fun, rewarding, and interactive. We use games, books, and other play activities to introduce your child to the study procedures and to develop rapport with your child.


Fill out the short screening form by clicking here

This screening form will ask a few questions regarding your family and child’s health history and sleep patterns.  This information will help us determine if your child qualifies for the study. Once you have completed this screening form, a study coordinator from our lab will contact you to schedule a phone conversation. 

Want more information?
Call 303-492-4584 or email