impressionable
adj.easy to influence or change your mind. You use this to describe someone who is young or not very experienced and might copy what they see.
adj.easily influenced or susceptible to the impact of external factors. Often used to describe individuals who lack a strong sense of self or are in a vulnerable developmental stage.
“The young child is very impressionable.”
“Because teenagers are so impressionable, they often adopt the habits of their favorite celebrities without thinking.”
“The witness was described as highly impressionable, suggesting that her testimony might have been significantly shaped by the leading questions posed by the attorney during the cross-examination.”
From French impressionnable, equivalent to impression + -able. See also impressible.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.