# Day 69: Cause and effect

> A classic experiment: 3-month-olds learn that a kick moves the mobile, and remember it. This month's first lesson: my actions make things happen. Kick and see.

- Series: Your third month, day by day (https://chorevia.com/learn/third-month), day 69 of 120, week 10
- Canonical URL: https://chorevia.com/learn/third-month/day-69
- Last reviewed: 2026-10-21
- Publisher: Chorevia (https://chorevia.com)
- Cite as: Chorevia. "Day 69: Cause and effect." Last reviewed October 21, 2026. https://chorevia.com/learn/third-month/day-69

This guide is general education that summarizes published research and guidance from groups like the American Academy of Pediatrics, the CDC, and the WHO. It isn’t medical advice, and every child develops on their own timeline. Your pediatrician knows your child; if something feels wrong, call them. In an emergency, call 911.

Today's idea is small and enormous: what your baby does changes what happens next.

## Heart

In a classic experiment, 3-month-olds learned to make a crib mobile move by kicking. They usually forgot the trick after about 8 days, but a brief reminder the day before testing let them remember it after 2 or even 4 weeks ([Rovee-Collier et al., 1980](https://pubmed.ncbi.nlm.nih.gov/7375924/)). How long babies remember this kind of lesson grows steadily from 2 to 18 months ([Hartshorn et al., 1998](https://pubmed.ncbi.nlm.nih.gov/9526683/)). A baby who forgets the trick next week hasn't lost anything; a reminder brings it back.

## Head

"My actions make things happen" is the first lesson on this month's list: a kick shakes the toy; a swipe makes the rattle sound ([Rovee-Collier et al., 1980](https://pubmed.ncbi.nlm.nih.gov/7375924/)). Simple cause-and-effect play is real learning. It works best as a conversation: everyday back-and-forth with you helps build connections in the brain ([Harvard Center on the Developing Child](https://developingchild.harvard.edu/key-concept/serve-and-return/)).

## Body

By month three, kicks get stronger ([AAP](https://www.healthychildren.org/English/ages-stages/baby/Pages/Movement-Birth-to-Three-Months.aspx)), and CDC suggests laying your baby on a blanket with safe toys to reach for and kick at ([CDC](https://www.cdc.gov/act-early/milestones/4-months.html)). The setting matters more than the toy: the floor, a blanket, you right there, and nothing left in the crib afterward ([Moon, AAP](https://www.healthychildren.org/English/ages-stages/baby/sleep/Pages/a-parents-guide-to-safe-sleep.aspx)).

## Try today

### Kick and see

- **Time:** A few minutes during floor play
- **From the guide:** [Kick and see](https://chorevia.com/learn/2-months#kick-and-see)

1. Lay your baby on their back on a blanket on the floor.
2. Place a crinkly or jingly soft toy where their feet can reach it.
3. When a kick makes a sound, say so: "You did that!"
4. Tomorrow, set the same toy in the same place and watch for a faster kick.

**Make it work:** Stay right there, and put the toy away when play is over ([CDC](https://www.cdc.gov/act-early/milestones/4-months.html)).

## Watch for

- **Normal:** harder kicking from one leg on some days. **Call your pediatrician** if your baby uses only one side of the body, or doesn't move both arms and both legs ([AAP](https://www.healthychildren.org/English/ages-stages/baby/Pages/Movement-Birth-to-Three-Months.aspx)).
- **Normal:** a trick that seems forgotten a week later ([Rovee-Collier et al., 1980](https://pubmed.ncbi.nlm.nih.gov/7375924/)). **Ask your pediatrician about developmental screening** if your baby has lost skills they used to have ([CDC](https://www.cdc.gov/act-early/milestones/4-months.html)).
- **Normal:** the toy heading for the mouth. Keep small, sharp, or hot things away ([CDC](https://www.cdc.gov/act-early/milestones/4-months.html)), and never tie a pacifier to the crib or around your baby's neck or hand ([AAP](https://www.healthychildren.org/English/ages-stages/baby/crying-colic/Pages/Pacifiers-and-Thumb-Sucking.aspx)). **Call 911** if your baby is struggling for each breath ([AAP](https://www.healthychildren.org/English/tips-tools/symptom-checker/Pages/symptomviewer.aspx?symptom=Breathing+Trouble)).

## For you

Cause and effect for you: one small thing that changes your day. Two with some evidence behind them. In a small lab study of 12 babies 1 to 6 months old, babies cried and moved less when their mother walked while carrying them than when she held them sitting ([Esposito et al., 2013](https://pubmed.ncbi.nlm.nih.gov/23602481/)). And in one study of 56 babies 6 to 12 weeks old, those who slept better at night got more daytime light, especially in the early afternoon, a link that doesn't prove cause ([Harrison, 2004](https://pubmed.ncbi.nlm.nih.gov/15560769/)). Put together: a walk after lunch with the baby in the carrier might change the afternoon and the night.

Water counts too: plenty of it, with fresh fruits and vegetables, is the plain advice for constipation ([Office on Women's Health](https://womenshealth.gov/pregnancy/childbirth-and-beyond/recovering-birth)).

If you're the partner: pick the one thing and do it unasked. Then notice what changed.

## Sources

- Rovee-Collier CK, Sullivan MW, Enright M, Lucas D, Fagen JW. "Reactivation of infant memory." Science, 1980. https://pubmed.ncbi.nlm.nih.gov/7375924/
- Hartshorn K, Rovee-Collier C, Gerhardstein P, et al. "The ontogeny of long-term memory over the first year-and-a-half of life." Developmental Psychobiology, 1998. https://pubmed.ncbi.nlm.nih.gov/9526683/
- Center on the Developing Child at Harvard University. "Serve and Return." 2026. https://developingchild.harvard.edu/key-concept/serve-and-return/
- Wusthoff CJ. "Movement Milestones: Birth to 3 Months." HealthyChildren.org, 2020. https://www.healthychildren.org/English/ages-stages/baby/Pages/Movement-Birth-to-Three-Months.aspx
- Centers for Disease Control and Prevention. "Milestones by 4 Months." Learn the Signs. Act Early., 2026. https://www.cdc.gov/act-early/milestones/4-months.html
- Moon RY. "How to Keep Your Sleeping Baby Safe: AAP Policy Explained." HealthyChildren.org, 2026. https://www.healthychildren.org/English/ages-stages/baby/sleep/Pages/a-parents-guide-to-safe-sleep.aspx
- American Academy of Pediatrics. "Baby Pacifiers & Thumb Sucking: What Parents Need to Know." HealthyChildren.org, 2026. https://www.healthychildren.org/English/ages-stages/baby/crying-colic/Pages/Pacifiers-and-Thumb-Sucking.aspx
- American Academy of Pediatrics. "Breathing Trouble" (symptom checker). HealthyChildren.org, 2026. https://www.healthychildren.org/English/tips-tools/symptom-checker/Pages/symptomviewer.aspx?symptom=Breathing+Trouble
- Esposito G, Yoshida S, Ohnishi R, et al. "Infant calming responses during maternal carrying in humans and mice." Current Biology, 2013. https://pubmed.ncbi.nlm.nih.gov/23602481/
- Harrison Y. "The relationship between daytime exposure to light and night-time sleep in 6-12-week-old infants." Journal of Sleep Research, 2004. https://pubmed.ncbi.nlm.nih.gov/15560769/
- Office on Women's Health. "Recovering from birth." US Department of Health and Human Services. https://womenshealth.gov/pregnancy/childbirth-and-beyond/recovering-birth