Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2012;7(11):e50862.
doi: 10.1371/journal.pone.0050862. Epub 2012 Nov 30.

Perceptual grouping and visual enumeration

Veronica Mazza  1 , Alfonso Caramazza
Affiliations

Perceptual grouping and visual enumeration

Veronica Mazza et al. PLoS One. 2012.

Abstract

We used lateralized Event-Related Potential (ERP) measures - the N2pc and CDA/SPCN components - to assess the role of grouping by target similarity during enumeration. Participants saw a variable number (0, 1, 2 or 3) of same- or differently-colored targets presented among homogeneous distracters, and performed an enumeration task. Results showed that the N2pc, but not the CDA, was larger for multiple targets of identical color relative to targets of different colors. The findings are interpreted in terms of the effects of grouping on early versus late stages of multiple object processing. Within this framework, they reveal that grouping has an effect on early individuation mechanisms, while later processing mechanisms are less prone to such an influence.

PubMed Disclaimer

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Stimuli and behavioral results.
(A) Example of a trial with three ungrouped targets on the right visual hemifield. (B) Mean RTs (with standard errors) as a function of target numerosity and similarity.
Figure 2
Figure 2. ERP results.
(A) The grand-average ERP difference waveforms show the larger N2pc on same relative to different color trials, both for two (left side) and three (right side) targets. Difference waveforms were obtained by subtracting ipsilateral activations from contralateral activations recorded at posterior sites (PO7, PO8, O1 and O2), collapsed across target side. (B) Left: The grand-average ERP difference waveforms, collapsed across same and different color trials, show the larger N2pc for larger numerosities. Right: N2pc and CDA mean amplitudes (with standard errors) as a function of target numerosity both in the same (white) and different (grey) color conditions. Amplitudes for one-target trials are depicted in black.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Pylyshyn ZW (2001) Visual indexes, preconceptual objects, and situated vision. Cognition 80: 127–158. - PubMed
    1. Kahneman D, Treisman A, Gibbs BJ (1992) The reviewing of object files: object-specific integration of information. Cogn Psychol 24: 175–219. - PubMed
    1. Trick LM, Pylyshyn ZW (1994) Why are small and large numbers enumerated differently? A limited-capacity preattentive stage in vision. Psychol Rev 101: 80–102. - PubMed
    1. Cavanagh P, He S (2012) Attention mechanisms for counting in stabilized and in dynamic displays. In: Brannon EM, Dehaene S, editors, Space Time and Number, Attention & Performance XXIV. Oxford University Press.
    1. Olivers CNL, Watson DG (2008) Subitizing requires attention. Vis Cogn 16: 439–462.

Publication types