Choose seed and control words

## Warning: Column `Word` joining factors with different levels, coercing to
## character vector

## Warning: Column `Word` joining factors with different levels, coercing to
## character vector

Plot productive knowledge of potential seed and control words

Words that should be good: cloth, color (verb), list
Known by too many kids to be worth teaching: piece, color (noun), sound, spill, noise, number, shape
(but, does saying it really mean you know it?)

Cloth

Piece

Color

Sound

Spill

Noise

Number

List

Shape

Plot receptive knowledge of potential seed and control words

Pretty high degree of overlap between productive and receptive understanding. So good words could be color, cloth, and list, but the rest are probably known by too many in this age range.