Age Range 4 to 12 months
The Experiment Download and print the three different line drawings of a spider below, and show them to your baby in any order you choose. Image A shows a simple illustration of a spider. Image B shows the same spider but with some of the features reconfigured. And in Image C, the spider's features are completely scrambled.
The Hypothesis Your baby will look longer at the normal image of the spider (Image A) than at the other two.
The Science When babies were shown these three images in a 2007 study published in Cognition, they gazed significantly longer at the unaltered spider image (an average of 24 seconds) than at either the partially reconfigured image (16 seconds) or the completely scrambled image (17 seconds). This suggests that babies have the innate ability to identify a spider -- one of the threats historically encountered by humans -- even if they've never seen one before. Talk about survival skills!
Age Range 2 to 4 months
The Hypothesis Your baby will soon make the connection that if she moves her arm, the mobile will move. However, her movements will vary depending on her age.
The Science In 2006, researchers in Japan conducted this experiment on 2-, 3-, and 4-month-olds to examine how a baby's understanding of cause and effect develops over time. The study found that the babies' movements became more specific with age: The 2-month-olds moved all four limbs roughly the same amount; the 3-month-olds moved their arms more than their legs; and the 4-month-olds moved the arm that had been attached to the mobile most of all. You can repeat this experiment every month to see how your child's understanding of cause and effect improves with age.
Age Range 6 to 12 months
The Experiment Place two similar toys in front of your baby and let him see you choose between them. As you move your hand toward the first toy, use negative facial expressions to show you're not interested in it -- such as wrinkling your nose or shaking your head -- without picking it up. Then, use positive facial expressions -- like smiling or raising your eyebrows -- as you pick up and play with the second toy. Put it back and encourage your child to choose one himself.
The Hypothesis Your baby is most likely to reach toward the same toy you chose.
The Science In a 2008 study published in Developmental Science, a group of 7-month-olds watched as an adult chose one of two toys. The children were then given the chance to select one of the toys themselves. More than half (58 percent) chose the same toy as the adult, suggesting that babies base their own desires on the perceived preferences of others. Your child takes cues from your behavior starting at a very early age, so make sure your own actions are ones you want her to emulate.
Age Range 2 to 6 months
The Experiment Shake a jingly toy close enough to your baby that she can reach out and touch it with her hands. Then dangle it close enough for her to touch with her feet if she moves them.
The Hypothesis Your baby will be able to touch the toy with her feet about a month before she can reach it with her hands.
The Science It's long been thought that babies gain control over their body in a top-down progression -- first head and neck, then arms and hands, then legs and feet -- but this experiment, based on a 2004 study published in Infant Behavioral Development, suggests that it's not that straightforward. On average, the infants in the study were able to touch the toy with their feet at 11.7 weeks and able to reach for and grasp a toy with their hands at 15.7 weeks. The hips have a more limited range of movement than the shoulders do, so it may be easier for your baby to make intentional leg movements -- which means she can master that motor skill earlier.
Age Range 0 to 6 months
The Experiment Put your awake, alert infant on his back. Press down firmly into the center of his palms with each of your thumbs and hold for a second.
The Hypothesis Your baby will open his mouth.
The Science Research has shown that most babies exhibit this response, known as the Babkin reflex, when pressure is applied to their palms. Named after the Russian researcher who studied it in the early 1950s, the Babkin reflex has a practical use for parents: If your newborn is not feeding well, apply pressure to his palms to get him to open his mouth to nurse or take a bottle.
Age Range 6 to 24 months
The Experiment Sit your baby in a high chair and spend a minute engaging with him: Smile, sing, and talk playfully. Then turn your head away briefly. When you turn back, gaze at him with a neutral expression.
The Hypothesis Your baby may attempt to engage with you by smiling, babbling, reaching out to you, or rapping on the high-chair tray. But he will soon become puzzled by your lack of response and may frown, yawn, look away, or cry. However, if you begin interacting with him again, he will quickly become content.
The Science This experiment shows that even young babies have a basic understanding of how social interaction works and can connect facial expressions with feelings. This is key to his understanding of your interactions with him, so be sure to use appropriate facial expressions when communicating with him. For instance, it might be difficult for a young child to understand that his hitting or biting has hurt you or one of his siblings, so grimace or wince to show what it means to feel hurt.
From Experimenting With Babies, by Shaun Gallagher. Reprinted by arrangement with Perigee, a member of Penguin Group (USA) LLC. Copyright © 2013 by Shaun Gallagher.
Originally published in the December 2014 issue of Parents magazine.