Infants with Down syndrome and their interactions with objects: Development of exploratory actions after reaching onset

• Infants with Down syndrome reached for and explored objects less than controls.
• The frequency of reaches increased in both groups of infants over a 2 month period.
• In Down syndrome infants no change in the amount of exploration was seen over time.
• Complexity and timing of exploratory actions were shaped by perceptual-motor skills.
• Reduced perceptual-motor experiences may have developmental consequences.

During infant development, objects and their functions are learned by means of active exploration. Factors that may influence exploration include reaching and grasping ability, object properties and the presence of developmental disorders. We assessed the development of exploratory actions in 16 typically-developing (TD) infants and 9 infants with Down syndrome (DS) after reaching onset. Infants with DS reached for and explored objects less frequently than TD infants, especially small objects. Over time, the amount of reaches increased in both groups, with no changes in the amount of exploration in the DS group. Pre-grasping actions were different across objects, but less efficient in generating action-relevant information in the DS group. These infants also performed fewer behaviors requiring complex motor skills. The results suggest that perceptual-motor abilities determine different exploratory behaviors in TD and DS infants. The reduced amount and complexity of exploratory actions may impact developmental outcome in DS.