As early as 1 1/2 to 2 years, children begin to talk about the past, guided by adults who prompt them and expand on their fragmented recollections.
( ( As ( early ( ( as ( ( 1 1/2 to ) 2 ) ) years ) ) ) ( , ( children ( ( begin ( to ( talk ( about ( ( ( the past ) , ) ( guided ( by ( adults ( who ( ( ( prompt them ) and ) ( expand ( on ( their ( fragmented recollections ) ) ) ) ) ) ) ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN As) (NP (JJ early) (QP (RB as) (CD 1 1/2) (TO to) (CD 2)) (NNS years))) (, ,) (NP (NNS children)) (VP (VBP begin) (S (VP (TO to) (VP (VB talk) (PP (IN about) (NP (NP (DT the) (NN past)) (, ,) (VP (VBN guided) (PP (IN by) (NP (NP (NNS adults)) (SBAR (WHNP (WP who)) (S (VP (VP (VB prompt) (NP (PRP them))) (CC and) (VP (VB expand) (PP (IN on) (NP (PRP$ their) (ADJP (JJ fragmented)) (NNS recollections)))))))))))))))) (. .)))
Children as young as 1 1/2 to 2 years will begin to talk about their past with no outside assistance. 
( ( Children ( as ( young ( ( as ( ( 1 1/2 to ) 2 ) ) years ) ) ) ) ( ( will ( begin ( to ( ( talk ( about ( their past ) ) ) ( with ( no ( outside assistance ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (NNP Children)) (PP (IN as) (NP (JJ young) (QP (RB as) (CD 1 1/2) (TO to) (CD 2)) (NNS years)))) (VP (MD will) (VP (VB begin) (S (VP (TO to) (VP (VB talk) (PP (IN about) (NP (PRP$ their) (NN past))) (PP (IN with) (NP (DT no) (JJ outside) (NN assistance)))))))) (. .)))