Jerome kagan's longitudinal research indicates that about 1 in 5 middle class european american toddlers cn be classified as

Jerome khagan's longitudinal research indicates that about 1 in 5 middle class European American toddlers can be classified as inhibited.

I believe the answer is: inhibited

Inhibited individuals refers to the individuals that make a conscious effort to avoid social interaction with other people. This does not make the toddlers necessarily would grow up to be bad at interaction, but their energy would most likely be depleted when they are around too many people, and would be recharged when they are alone.