The figural simplicity or salience of parallel lines was studied in 3- and 4-year-olds by means of a figural matching procedure where parallelism was a basis for judging similarity. (Author/JMB)

The conservation of distance and of length and the awareness of the horizontal and of the vertical do seem to significantly precede the measurement of length, but the results did not indicate that these four tasks have any developmental order among themselves. Bibliography, charts. (Author)

Results clearly demonstrated the existence of perceptual sets in children under 4 years. The interpretation of findings suggests a process whereby the present method was successful in creating the mediating conditions necessary for a perceptual set. (Authors)

The growth of spatial awareness and representation was studied in children between ages five and nine. A group of thirteen tasks was administered to subjects three times with periods of approximately six months among sessions. The tasks were selected to measure understanding of projective spatial properties (straight line trajectories,…