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Crowding and surround suppression: not to be confused.
Yury Petrov1, Ariella V Popple, Suzanne P McKee
1Psychology Department, Northeastern University, Boston, MA 02115, USA. y.petrov@neu.edu
Journal of Vision
|January 26, 2008
Summary
Crowding and surround suppression are distinct visual phenomena. Crowding shows directional masking effects at fine scales, unlike surround suppression observed at all scales.
Area of Science:
- Visual perception
- Neuroscience
- Psychophysics
Background:
- Crowding and surround suppression are visual phenomena with overlapping characteristics, suggesting a potential common mechanism.
- Previous research has inconsistently compared these phenomena, leading to debates about their relationship.
- A 2002 study suggested they are unrelated due to differing effect strengths.
Purpose of the Study:
- To systematically compare crowding and surround suppression using identical stimuli and tasks.
- To investigate the role of masking directionality and scale in differentiating these visual processes.
- To clarify the relationship between crowding and surround suppression.
Main Methods:
- Employed a Gabor target for both orientation identification (crowding) and contrast detection (surround suppression) tasks.
- Investigated the effect of outward versus inward masking on the orientation identification task.
- Assessed masking effects across different visual scales and target contrasts.
Main Results:
- Orientation identification (crowding) exhibited anisotropic masking, with outward masks being more effective than inward masks.
- Contrast detection (surround suppression) showed no such anisotropy.
- Anisotropic masking characteristic of crowding was observed only at fine visual scales, while surround suppression occurred at all scales.
Conclusions:
- Crowding and surround suppression are distinct visual phenomena.
- The characteristic anisotropy of crowding is scale-dependent, differentiating it from surround suppression.
- A common crowding paradigm varying target contrast may confound crowding with surround suppression, especially at low contrasts.
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