A sample of 40 children aged six to eight years took part in a balanced repeated measures design experiment in which conservation of liquid quantity was assessed in two different conditions. The first condition comprised the traditional Piagetian paradigm. The second condition employed sealed bottles which were inverted or otherwise manipulated to achieve transformations. Moreover, in this condition the need to ask the critical conservation question twice (inherent in the traditional procedure) was avoided by requiring children to select pairs of bottles from an array of four bottles and children were also allowed to make the transformations themselves. The results showed that more children conserved in the ‘bottles’ conditon.