Object and event representation in toddlers.

Mental representation of absent objects and events is a major cognitive achievement. Research is presented that explores how toddlers (2- to 3-year-old children) search for hidden objects and understand out-of-sight events. Younger children fail to use visually obvious cues, such as a barrier that blocks a moving object's path. Spatiotemporal information provided by movement cues directly connected to the hidden object is more helpful. A key problem for toddlers appears to be difficulty in representing a spatial array involving events with multiple elements.