The purposes of this thesis were to study three - to - four - year – old children’s ability to search for object undergone invisible displacement, to predict their above chance ability to search for object, and to analyze their error patterns in selecting doors to search for the object. The subjects consisted of 96 children,48 boys and 48 girls. The equipment was modified from the study of Berthier et al. (2000) to suit Thai children. One-way ANOVA was used for statistical analysis. The study showed that : 1. Three - and - a - half and 4-year-old children had significantly better ability to search for object undergone invisible displacement than the 3 -year – olds (p<.05). However, there was no difference between 3 ½ and 4 -year-old children's ability to search for the invisibly displaced object. 2. The proportion of children’s above chance ability to search for object undergone invisible displacement increased in accordance with their increasing age. 3. There were three error patterns found in 3,3 ½ and 4 year-old children’s search for the invisible object : AB error (38.97%,9.38%, and 31.25%, respectively), favorite door (28.68%, 18.75%, and 31.25%, respectively), and adjacent doors (36.26%, 31.25%, and 37.5%, respectively).
