Introduction
This interview is based on the game "Number Between". When playing this game, Caitlin shows how she perceives the decimal part of a number as another whole number. Often she ignores the decimal point completely. She finds it easy to think of numbers between 0.0 and 1.0, between 0.0 and 0.5 and between 0.3 and 0.5 because these can be done by ignoring the decimal point. However, she cannot agree that there is a number between 0.4 and 0.5, even when the interviewer suggests one and the computer game that she is playing accepts it.

Comments: Text in italics
Interviewer: Text in red
Caitlin: Text other colour

Interviewer:
In this game you have to think of a number between the two numbers given

The first case presented by the computer is to type in any number between 0.0 and 1.0

Caitlin:
5 is between nothing and 10

Caitlin seems to ignore the decimal point.

Caitlin types a 5. Then the computer tells her it is too large.

Caitlin:
Oh, I forgot the point

Interviewer:
Try again

Caitlin types 0.5. The computer accepts this, shows it on the number line, then presents the new interval 0.0 to 0.5.

Interviewer:
Good

Caitlin:
Now nothing to 5...I'll try 3

Caitlin ignores the decimal point again and types 3.

The computer rejects the 3.

Caitlin:
No...point 3

Caitlin types 0.3 which the computer accepts. The computer then presents the interval 0.3 to 0.5

Caitlin:
Easy, point 4

Caitlin types 0.4 and the computer presents the interval 0.4 to 0.5.

Caitlin:
But there is no number between 4 and 5...Unless maybe 4 and a half...4 point 5?

Caitlin types 4.5 and the computer tells her it is too large

Caitlin:
There isn't a number!!

Interviewer:
Try point 4 5

Dubiously, Caitlin types 0.4 5 which is accepted by the computer.

Caitlin:
But that doesn't make sense because 45 is bigger than 5??!!

Caitlin believes that 0.45 is larger than 0.5. She is simply comparing 45 small pieces with 5 small pieces.