Non-verbal and verbal judgements of length invariance by young children.

One hundred and fifty non-conservers in length were assessed for their ability to make a non-verbal judgement of length invariance on a task employing a train-transfer design in which the stimuli were pairs of pencils. Seventy per cent of the children from the group who had to respond to length equality as opposed to inequality made the correct invariance judgement and could, moreover, characterize their choices in invariance language (e.g. 'same size') whilst still failing the standard verbal task in which such phrases were used by the experimenter. This is regarded as supporting the hypothesis that the non-conserver's linguistic difficulty is not with framing the verbal judgement but in interpreting a question which he believes has to be interpreted unidimensionally in such a context of perceptual change.