Do Circadian Rhythms Change with Age?

based on 8 ratings
Author: Megan Doyle

Grade Level: 9th to 12th; Type: Social Science


This experiment will assess whether the timing of peak mental performance shifts from afternoon to morning as we age.

Research Questions:

  • Do some age groups have better mental function in the morning?
  • Do some age groups have better mental function in the late afternoon/early evening?

As you age, does it become easier to rise early and complete activities in the morning? This experiment will evaluate morning and evening mental function in a variety of age groups.


  • Approximately 20 test subjects in each age group (eg, high school, young adult, middle age, and older adult). Include an equal number of males and females in each group.
  • Several mental tasks (eg, 50 piece puzzle, multiplication test, etc)
  • Computer
  • Printer
  • Notebook for analyzing results

Experimental Procedure:

  1. Put together several mental tests to give to your test subjects. Make sure that each task that you put together can be easily altered. You want the test to look different to your test subjects each time they take it (try not to alter the difficulty of each test when you revise them).
  2. Ask participants to make sure that they get the same amount of sleep each night during the two days that you complete this experiment.
  3. For each age group, 10 participants should be tested in the morning first and 10 participants should be tested in the late afternoon/early evening first.
  4. Time how long it takes half of the participants in each age to perform your mental tasks early in the morning (around 8 am).
  5. Time how long it takes the other half of the participants in each age group to perform the mental tasks in the late afternoon/early evening (around 5 pm).
  6. The next day, repeat steps 3 and 4. Participants that were tested in the morning should now be tested in the evening and vice versa. Remember to slightly alter your mental tasks so that they appear “new” to your test subjects. Record the time it takes for each participant to complete the tasks.
  7. Analyze your results. Look at the amount of time it took each participant to perform each mental task in the morning versus the late afternoon/early evening. Also evaluate the average time it takes participants in each age group to complete all tasks in the morning versus the evening. Do certain age groups seem to perform the tasks faster in the morning? What percentage of older adults show an improvement in the time it takes to complete the tasks when they work in the early evening versus the morning? How does this percentage compare to that of younger adults or teenagers?

Terms/Concepts: How do circadian rhythms change with age?

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