Compare two things

What it looks like when your child can do it

• — Given two slices of bread on two plates, your child says both came from the same loaf and sit on the same shelf, and only one is inside a plastic bag.
• — Your child makes two lists, Same and Different, instead of one long jumbled answer.
• — Your child notices a difference you did not point out, like one of the two slices being cut a little thicker.

How to teach it at the kitchen table

1. 01

   Set two real things side by side

   Two cups, two socks, two apples. Put them close together so your child's eyes can go back and forth between them. Comparing from memory is much harder.

2. 02

   Make two columns, Same and Different

   Draw a line down a sheet of paper. Everything your child notices goes on one side or the other. The columns keep the answer from turning into one long sentence.

3. 03

   Go one feature at a time

   Ask about one feature: size, color, what is inside, where it sits, how full it is. Your child looks at both things before deciding, then moves to the next feature.

4. 04

   Change one thing while they watch

   Flatten one of two matching balls of play dough, or tie a ribbon on one of two matching toy cars. Ask what is different now. A fair test is built on this move, so do it a few times with different changes.

You will need: Two matching plates and two slices of bread · A plastic bag · Paper with a line down the middle

Try it together

1. Try 1

   Set two matching slices of bread on two matching plates, and slip one slice into a plastic bag. Ask what is the same and what is different.

   Listen for  Same: the bread, the plates, the spot on the counter. Different: one is in a bag. Listen for the Same list as well as the difference.

2. Try 2

   Now carry the plate with the unbagged slice to the top of the refrigerator. Ask again what is different.

   Listen for  Two things are different now: the bag and where each plate sits. Watch that your child finds both, not only the one you moved.

3. Try 3

   Hold up two socks that are not a pair. Ask for three things that are the same and three that are different.

   Listen for  Answers depend on the socks. Each one should name a feature, like color, length or thickness, and say what each sock is like.

4. Try 4

   Describe two matching toy cars rolled down the same board from the same spot, but one has a lump of clay pressed on top. Ask what is different.

   Listen for  Only the lump of clay, which means how heavy each car is. Everything else matches.

Watch for

• — Naming only differences. The Same list is half the skill, because a fair test lives in what stays the same.

If it is not there yet

• — Start with two things that differ in only one way, like two matching plates with a cracker on only one, and add a second difference later.
• — Name one feature at a time, such as color or size, and ask only about that feature until your child is ready for the next.

A few days of this is normal, and it is time well spent. The lesson will still be there, and it will go faster.

Where this skill comes up

• How Scientists Actually Find Out · Lesson 16

  Everything Else Stays the Same

  Needs it because each item on the sheet asks what is the same and what is different between two set-ups.

• How Scientists Actually Find Out · Lesson 17

  The Cup You Do Nothing To

  Needs it because A control only makes sense to a child who can hold two set-ups side by side and say what differs.