A study [1] has found that adults were better able to remember pictures of imaginary animals than real animals (they used pictures of real cats).

Their theory is that when you have little/no knowledge of the subject you can approach it with a child-like sense of naïveté. As you gain further knowledge of the subject you begin to categorise which allows you to consider complicated subject matter in a more structured form but at the cost of losing detail.

“If you categorize a person, you will be less likely to remember individual details about the person.”

This is relevant to kanji study, as here we must balance categorising the kanji by exploiting a structure (Heisig’s ordering based on the primitives) with remembering individual details between characters, e.g. the difference between 待 and 持。

The results of this study suggest an inverse relationship between categorisation performance and recollection of fine detail. Encouragingly, the adults in the study were able to match the ability of children when studying completely made-up material. This lends some support to Heisig’s assertion that learning the etymology of the kanji is likely to be a hindrance rather than a help. It also suggests that categorisation should be used sparingly otherwise we could fall into the trap of simply recognising “characters which contain 寺” instead of distinguishing 待 and 持。

待　持

[1] Too much knowledge can be bad for some types of memory, study finds