View source for Physics:Numerosity adaptation effect

{{Short description|Phenomenon in numerical cognition}}
{{Cognitive}}
[[File:Numerosityadaptation.png|thumb|left|upright=1.5|alt=Two figures, one above the other. First figure (up) display contain two circles: 10 dots in the circle at left and 100 dots in the circle at right. Fixation mark is placed between two circles. The second figure display contain two circles with each of them contain 40 dots. The dots in the left circle are arranged as mirror image of the dots in the right circle|An example of the numerosity adaptation effect]]
The '''numerosity adaptation effect''' is a [[Perception|perceptual phenomenon]] in [[Philosophy:Numerical cognition|numerical cognition]] which demonstrates non-symbolic [[Number sense|numerical intuition]] and exemplifies how numerical percepts can impose themselves upon the human brain automatically. This effect was first described in 2008.<ref name=Dehaene>{{cite journal |title=Origins of Mathematical Intuitions The Case of Arithmetic |journal=Annals of the New York Academy of Sciences |date=2009 |first=Stanislas |last=Dehaene |volume=1156 |pages=232–259 |pmid=19338511 |doi=10.1111/j.1749-6632.2009.04469.x|s2cid=2382715 }}</ref><ref name=Burr&Ross>{{cite journal |title=A Visual Sense of Number |journal=Current Biology |date=2008 |first=David |last=Burr |author2=John Ross |volume=18 |issue=6 |pages=425–428 |pmid=18342507 |doi=10.1016/j.cub.2008.02.052 |doi-access=free }}</ref>

Presently, this effect is described only for controlled experimental conditions. In the illustration, a viewer should have a strong impression that the left display (lower figure) is more numerous than the right, after 30 seconds of viewing the adaptation (upper figure), although both have exactly the same number of dots. The viewer might also underestimate the number of dots presented in the display.<ref name=Dehaene/>

Both effects are resistant to manipulation of the non-numerical parameters of the display. Thus, this effect cannot be simply explained in terms of size, density, or contrast.<ref>{{cite journal |title=Calibrating the mental number line |journal=Cognition |date=2008 |first=Véronique |last=Izard |author2=Stanislas Dehaene  |volume=106 |issue=3 |pages=1221–1247 |pmid=17678639 |doi=10.1016/j.cognition.2007.06.004 |url=http://www.google.co.il/search?hl=iw&q=%22Calibrating+the+mental+number+line%22&btnG=%D7%97%D7%99%D7%A4%D7%95%D7%A9&meta=&aq=f&aqi=&aql=&oq=&gs_rfai= |format=PDF |access-date=2010-04-01|citeseerx=10.1.1.148.2960 |s2cid=9488163 }}</ref><ref name=Burr&Ross2/>

Perhaps the most astonishing aspect of these effects is that they happen immediately, and without conscious control (i.e., knowing that the numbers are equal would not hamper their happening).<ref name=Dehaene/> This points to the operation of a special and largely automatic processing system. As noted by Burr & Ross (2008):

{{cquote|''Just as we have a direct visual sense of the reddishness of half a dozen ripe cherries, so we do of their sixishness.''<ref name=Burr&Ross/>}}

==Possible explanations==
Few explanations were suggested to explain these phenomena. It was argued that they are heavily dependent on density and less on numerosity. Also, it was suggested that numerosity may be correlated with [[Kurtosis|kurtosis]] and that the results may be better explained in terms of texture density such that only dots falling within the spatial region where the test is displayed effectively adapt the region.<ref>{{cite journal |title=Texture density adaptation and visual number revisited |journal=Current Biology |date=September 23, 2008 |first=Frank H |last=Durgin |volume=18 |issue=18 |pages=R855–R856 |pmid=18812077 |doi=10.1016/j.cub.2008.07.053 |doi-access=free }}</ref>

However, as the display in the original experiments was of spots uniformly either white or black, the kurtosis account is inapplicable. The texture density explanation doesn't seem to disentangle the complexity of these phenomena as in the display the left field adapts to many dots, the right field to few, and these adapters selectively affect the relevant test stimuli. It is not the number of dots in the entire display that causes the adaptation but only those within a particular area.<ref name=Burr&Ross2>{{cite journal |title=Response: Visual number |journal=Current Biology |date=September 23, 2008 |first=David |last=Burr |author2=John Ross |volume=18 |issue=18 |pages=R857–R858 |pmid=<!--none--> |doi=10.1016/j.cub.2008.07.052 |doi-access=free }}</ref> At present, why adaptation have such profound effect on numerosity estimates remains largely unexplained.<ref name=Dehaene/>

==See also==
{{Commons|Optical illusion|Numerosity adaptation effect}}
*[[Approximate number system]]
*[[Philosophy:Numerical cognition|Numerical cognition]]
*[[Number sense]]
*[[Numeracy]]

==References==
{{reflist|2}}

[[Category:Optical illusions]]
[[Category:Cognition]]
[[Category:Perception]]

{{Sourceattribution|Numerosity adaptation effect}}