 It is worth noting that evidence from developmental psychology indicates some meaning is pre-linguistic and that some pre-linguistic meaning or conceptual content relate to situations that are not detectable by the child. For example, psychologists have discovered systems of core knowledge activated in infancy that govern the representation of, inter alia concrete objects and human agents [see Spelke 2003; Spelke and Kinzler 2007]. An interesting finding from preferential gaze experiments suggests 4 month old infants represent occluded objects as continuing behind their  barriers.[5]