Sara Giovagnoli, Elena Bertossi, Sara Magri, Luca Mendolesi, Roberto Bolzani, Mariagrazia Benassi

A test for the evaluation of form perception ability: Form Coherence Test

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Keywords: form coherence, visual form detection, ventral stream, visual perception, form discrimination.

The aim of this study is the assessment of the applicability of the Form Coherence Test in a population of infants and adolescents. The Form Coherence Test is a computerized test for the evaluation of form perception ability. The subject is asked to discriminate a shape-stimulus among eight possible forms. The form perception is obtained by spatial coherent luminance dots visualized on a black background. Stimuli are presented in five levels of coherence which determine the difficulty of the task: starting from the 100% of coherence level, the number of the coherently aligned dots exponentially decreases while the number of non-coherent dots (noise) increases. A sample of two hundred and fifty children (range 5-12 years) took part in the study. Accuracy is measured as the number of correct answers for each coherence level and for each stimulus. The Generalized Estimating Equation Model shows that the form perception accuracy decreased significantly in the subsequent coherence levels, starting from the 98% to 45%. The number of correct answers raised significantly with age. Age also affects the identification of the eight forms characterized by different difficulty. The results showed that Form Coherence Test is an adeguate instrument for the considered ages and allowed to evaluate the subject's performance at different coherence level taking into account the age.

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