Well-known theories of child development'Freud's, Skinner's, Gesell's, and Piaget's, for example'provide little comfort, since dramatic shifts in favored theories have occurred since the launching of systematic study of children about 100 years ago.
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(ROOT (S (S (NP (NP (JJ Well-known) (NNS theories)) (PP (IN of) (NP (NP (NN child) (NN development)) (`` `) (NP (NNP Freud))))) (VP (VBZ 's))) (, ,) (S (NP (NNP Skinner) (POS 's))) (, ,) (S (NP (NNP Gesell) (POS 's))) (, ,) (CC and) (S (NP (NNP Piaget)) (VP (VBZ 's) (, ,) (SBAR (IN for) (S (NP (NN example)) (VP (`` `) (VBP provide) (NP (JJ little) (NN comfort))))) (, ,) (SBAR (IN since) (S (NP (NP (JJ dramatic) (NNS shifts)) (PP (IN in) (NP (JJ favored) (NNS theories)))) (VP (VBP have) (VP (VBN occurred) (PP (IN since) (NP (NP (DT the) (NN launching)) (PP (IN of) (NP (NP (JJ systematic) (NN study)) (PP (IN of) (NP (NNS children))))))) (ADVP (NP (QP (RB about) (CD 100)) (NNS years)) (RB ago)))))))) (. .)))
Freud, Skinner, Gesell and Piaget all studied child development.
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