Understanding of 'chunking'

A teacher gave her class the task of making a 'train' of nine cubes in a repeating AAB pattern.

Then she asked the students to show the unit of repeat by breaking their row apart.

As the students worked, the teacher noticed that most students had correctly broken their rows into three lots of three cubes.

However several of them did not have their units aligned.

Units of repeat not aligned.

Some even had one of them reversed.

One unit of repeat reversed.

The teacher was unsure whether these students realised that the unit of repeat is fixed.

So she asked them if all three of their 'chunks' were the same and, if so, to show it.

Here is what one student did.

Units of repeat aligned.

Now the teacher was sure that the students did realise that all the units of repeat must be identical.