Discriminability and Set Size

The finding that, as numerosity increases, discrimin-ability of a give numerical difference decreases is a robust effect, found within animals, human infants, and human adults. In an experiment in which rats were required to discriminate two from three and three from four sounds, all three subjects successfully discriminated two from three, but only two learned to discriminate three from four. Similarly, in an experiment requiring squirrel monkeys to pick out the smaller of two simultaneously presented arrays of objects, subjects were able to distinguish six from seven and seven from eight, but only one subject was able to distinguish eight from nine. Discrimination of adjacent numbers by human infants is also stronger with smaller numerosities. Two studies obtained results in which infants discriminated two from three but not four from six; in another study, infants discriminated two objects from three reliably, discriminated three from four only in certain situations, and did not discriminate four from five. In yet another study, three different ages of infants discriminated two objects from three and three from four, but only the oldest age groups (8- and 13-month-olds) discriminated four from five. These results, though obtained with a very different methodology, parallel the finding that human adults also show an effect of set size, even within the subitization range, when asked to rapidly identify the numerosity of an array; the identification of numbers is both faster and more error-free the smaller the number.

However, both animals and human infants are able to represent approximate values of larger numbers and to discriminate two numbers when the proportion by which they differ is sufficiently large. When rats are trained to press a lever a minimum required number of times in order to obtain a reward, the variance of their response increases with the required number, but they are nonetheless able to perform this task even with numbers as high as 50 (the largest tested). Human infants can discriminate 8 items from 16 and 16 from 32, with nonnumerical factors such as area, density, and contour length controlled.

Understanding And Treating Autism

Understanding And Treating Autism

Whenever a doctor informs the parents that their child is suffering with Autism, the first & foremost question that is thrown over him is - How did it happen? How did my child get this disease? Well, there is no definite answer to what are the exact causes of Autism.

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