Solution: Science Diagrams
Answer: PEDAGOGY

Written by Diane Heaton, Sara Goodchild and Michael Sylvia; artwork by Matt Smith

These diagrams are about topics you might see explained in a science textbook - but something's clearly odd about them. The "double-take" flavourtext may suggest that there are two things to be found in them, and in fact, each one has a second topic, seemingly extraneous, thrown in.

If you write down what both topics are for each diagram, you may notice that the lengths of the words match within each one. For example, Figure 1 illustrates a MERCATOR PROJECTION, but uses terms from FREUDIAN PSYCHOLOGY.

Not only do these phrases have the same word lengths, they all have exactly one letter in the matching position. Taking these shared letters, in order by figure, gives the answer PEDAGOGY - appropriate for educational diagrams.

In given order:

Figure Topic 1 Topic 2 Invariant letter
1 MERCATOR PROJECTION FREUDIAN PSYCHOLOGY P
2 TORQUE CHEESE E
3 DOUBLE HELIX DENTAL FLOSS D
4 MAGNETIC FIELD BACTRIAN CAMEL A
5 BIG BANG DOG SLED G
6 GOITER WOMBAT O
7 RIGHT HAND RULE SUGAR SNAP PEAS G
8 WATER CYCLE COUGH SYRUP Y