Two experiments are described. In Exp. 1, subjects compared the apparent numerosity of two kinds of dot patterns, regular vs irregular, with two different exposures (160 vs 2000 msec). In Exp. 2, the subjects had to estimate the numerosity of the same patterns, presented one at a time. Analysis showed a relative overestimation of the regular patterns in Exp. 1 but not in Exp. 2. In general an overestimation occurred with an increase in exposure. Such results support our hypothesis of two separate processes as the basis of the two kinds of performance (estimating vs comparison).
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References
1.
AokiT.On the counting process of patterned dots. Tohoku Psychologica Folia, 1977, 36, 15–22.
2.
BurgessA.BarlowH. B.The precision of numerosity discrimination in arrays of random dots. Vision Research, 1983, 23, 811–820.
3.
De MarchiS.L'apprezzamento di collettivitá. Archivio italiano di Psicologia, 1929, 7, 177–225. (a).
4.
De MarchiS.Illusioni ottiche e apprezzamento di collettività. Atti del IX Congresso degli Psicologi Italiani. Bologna (separatum), 1929. (b).
5.
GinsburgN.Effect of item arrangement on perceived numerosity: randomness vs regularity. Perceptual and Motor Skills, 1976, 43, 663–668.
6.
GinsburgN.Perceived numerosity, item arrangement, and expectancy. American Journal of Psychology, 1978, 91, 267–273.
7.
GuilfordJ. P.Psychometric methods. New York: McGraw-hill, 1954.
8.
HunterW. S.SiglerM.The span of visual discrimination as a function of time and intensity of stimulation. Journal of Experimental Psychology, 1940, 26, 160–179.
9.
LecheltE. C.NelsonT. M.Numerosity discrimination under varying conditions of steady illumination. Journal of General Psychology, 1971, 84, 121–132.
10.
LiebenbergR.über das Schätzen von Mengen. Zeitschrift für Psychologie, 1914, 68, 321–395.
11.
LuccioR.Formazione di sottogruppi e percezione di numerosità. Archivio di Psicologia, Neurologia e Psichiatria, 1981, 42, 463–476.
12.
LuccioR.Densitã apparente e percezione di numerosità. In Cesa-BianchiM. (Ed.), Ricerche di laboratorio e intervento nella società. Milano: Unicopli, 1982. Pp. 135–144.
13.
LuccioR.RodaniM. G.Illusioni di lunghezza e illusioni di numerositi. In KanizsaG. (Ed.), Penomenologia sperimentale della visione: ricerche di psicologia. Milano: Franco Angeli, 1984. Pp. 259–265.
14.
TavesE. H.Two mechanisms for the perception of visual numerousness. Archives of Psychology, 1941, 37, 1–47.
