 The second is the research of Flavell,  which studied children's growing abilities to judge other people's conceptual and perceptual perspectives.
<meaning-changed>  The second is the research of Flavell,  which studied children's growing abilities to judge other people's conceptual and perceptual perspectives.
 The second is the research of Flavell, Sons. . ERIC ID:ED027082. which studied children's growing abilities to judge other people's conceptual and perceptual perspectives.