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I'm wondering, how many objects can the average human being can recognize?

For example, most of us can't look at this and say how many boxes there are without counting them:

lots of boxes

But I think we can all recognize that there are only 3 boxes here (without manually counting):

3 boxes

So how many objects can an average human being recognize at once?

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1 Answer

up vote 10 down vote accepted

The ability to enumerate objects without counting is known as subitizing.

Most studies suggest that we can subitize up to about 3 or 4 items (e.g. Starkey & Cooper, 1995). Enumeration of a small number of objects (i.e. subitizing) yields consistent response times regardless of the quantity of objects. Enumeration of larger quantities (i.e. counting) yields response times that increase linearly with the number of objects. This is taken as evidence that the two processes are computationally distinct.

Further studies in both neuropsychology (Dehaene & Cohen, 1994) and neuroimaging (Piazza et al., 2002) have supported the idea that separate neural substrates underly the two computational processes.

References

Dehaene, S., & Cohen, L. (1994). Dissociable mechanisms of subitizing and counting: Neuropsychological evidence from simultanagnosic patients. Journal of Experimental Psychology-Human Perception and Performance, 20(5), 958-975. PDF

Piazza, M., Mechelli, A., Butterworth, B., & Price, C. J. (2002). Are subitizing and counting implemented as separate or functionally overlapping processes?. Neuroimage, 15(2), 435-446. PDF

Starkey, P., & Cooper, R. G. (1995). The development of subitizing in young children. British Journal of Developmental Psychology, 13(4), 399-420.

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Thanks a lot! This completely answers my question :D –  MiJyn May 1 '13 at 21:57
    
Well, I can subitize up to at least six items. It depends on the size, shape and position of the objects. From a a life long handling of eggs, apples and other objects of similar size and shape, I find I can recognize with one quick gaze if there are five or six apples. I'm sure you all can, too. I did not read the articles, but obviously that research, if it finds the highest number is three or four, is not very applicable to everyday behavior. –  user1196 May 3 '13 at 15:36
    
@what the average is about 4, but there is definitely a range. you may be on the high end of the spectrum. there are two other alternatives i can think of: for eggs in a carton, you may simply be recognizing specific spatial patterns and associating them with numeric quantities. similarly for apples or other objects, perhaps you're using total spatial area as a proxy for quantity. these are not really subitizing, as they are domain-specific and rely on expertise. –  Jeff May 3 '13 at 17:35
    
also remember that if you can subitize 4 items, counting to 5-6 will only tack on about 250-500ms, a very short amount of time. so i think it's difficult to establish whether you're counting or subitizing without using more controlled chronometry –  Jeff May 3 '13 at 18:49
    
It is also important to note that subitizing can be confounded with pattern recognition with regard to canonical dot patterns (for example, the dots on the sides of a pair of dice), as those are easier to recognize than any other random arrangement of n objects, given n>3. The fact that it is difficult, if not impossible, to avoid canonical arrangements for n of 4 or less is also important. –  Jonathan Thiele Aug 29 '13 at 19:00
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