Etienne, Ariane S. <br/><br/>
The meaning of object permanence at different zoological levels 

 - 1984 
<br/><br/> The nature of the object concept is reviewed at various zoological levels, and special importance is given to the noiton of its continued existence. 
<br/><br/><label>Subjects--Index Terms: </label>Comparative psychology cognitive development object permanence