The children today carried out a fair test to compare how well they were able to hear each other using hand made string telephones. They decided to compare their telephone with someone else's who had either longer or shorter string, a different type of string or someone who pulled their string tighter. They were fantastic at reasoning why their telephones worked better when the string was tighter, shorter or had a thinner string, explaining about how sound vibrations had to move along the string to get to their partners ear and it needed to be tight and thin and close.