Almeida, A., Arantes, J. & Machado, A.(2007).
Numerosity discrimination in preschool children.
Journal of the Experimental Analysis of Behavior, 88, 339-354.
We used a numerical bisection procedure to examine preschool children’s sensitivity to the numerical attributes
of stimuli. In Experiment 1 children performed two tasks. In the Cups Task they earned coins for choosing a green
cup after two drumbeats and a blue cup after eight drumbeats. In the Gloves Task they earned coins for raising a
red glove on their left hand after two drumbeats and a yellow glove on their right hand after eight drumbeats.
Then in each task a psychometric function was obtained by presenting intermediate numerosities and recording the
percentage of trials in which children chose the “many” option. In Experiment 2 children’s performance in a “2
vs. 8” discrimination was compared with their performance in a “4 vs. 16” discrimination. Results showed that the
individual psychometric functions were of two types, one in which the percentage of “many” choices increased
gradually with stimulus numerosity and another in which it increased abruptly, in a step-like manner. Although
the average point of subjective equality was close to the geometric mean of the anchor numerosities and the
average functions for “2 vs. 8” and “4 vs. 16” superimposed when plotted on a common scale (the scalar property),
the individual data were highly variable both across tasks (Cups and Gloves) and numerosity ranges (“2 vs. 8”
and “4 vs. 16”). It is suggested that between- and within-subjects variability in the psychometric function is
related to children’s verbalizations about the sample stimulus.
Key words: bisection procedure, numerosity discrimination, point of subjective equality, psychometric function, scalar property, children