In the piloting the students' responses to the task "Area" from diagnostic test 1 can be divided into 4 categories.

Graph-as-picture error
Some students made a graph-as-picture error and reasoned their answer just with the shape of the graph. A typical answer was:
Because the drawing at the top looks exactly like the on I have circled.

Graph-as-picture error
Some students already argued with the area but they still took the shape into account. Typical answer: Because the area increases and then stays the same.

Correct answer
... but wrong reasoning showed that the students did not interpret the diagram correctly.

Correct answer
Some students chose the correct diagram with an explanation as follows: Because the grey piece is getting bigger or similar answers.