The regular-random numerosity illusion: rectangular patterns.

The overestimation of regular patterns compared with random patterns, previously reported for circular displays, was replicated with the use of rectangular displays of dots and controlling for overall area. Twelve female and four male college students with an average age of 27.3 years estimated the number of elements in 10 patterns containing from 45 to 126 dots. The results were discussed in relation to a suggestion of Frith and Frith, according to which better Gestalten appear more numerous.