Abstract
Groupitizing is a recently described phenomenon of numerosity perception where clustering items of a set into smaller “subitizable” groups improves discrimination. Groupitizing is thought to be rooted on the subitizing system, with which it shares several properties: both phenomena accelerate counting and decrease estimation thresholds irrespective of stimulus format (for both simultaneous and sequential numerosity perception) and both rely on attention. As previous research on groupitizing has been almost completely limited to vision, the current study investigates whether it generalizes to other sensory modalities. Participants estimated the numerosity of a series of tones clustered either by proximity in time or by similarity in frequency. We found that compared with unstructured tone sequences, grouping lowered auditory estimation thresholds by up to 20%. The groupitizing advantage was similar across different grouping conditions, temporal proximity and tone frequency similarity. These results mirror the groupitizing effect for visual stimuli, suggesting that, like subitizing, groupitizing is an a-modal phenomenon.
Highlights
Humans exploit various strategies to gauge the number of objects in a set, including serial counting and approximate estimation
The results revealed that auditory grouping cues had no measurable effect on average perceived numerosity, but they decreased estimation thresholds by up to 20%, similar to the advantage previously reported for spatial arrays
The groupitizing advantage occurred for both grouping conditions, both when groups were defined by manipulating the temporal proximity of the tone, as well as when they were defined by similarity of tone frequency
Summary
Humans exploit various strategies to gauge the number of objects in a set, including serial counting and approximate estimation. Estimation is relatively fast, it is prone to errors, with response variability (standard deviation of the estimates) tending to scale linearly with the number of objects (Weber Law) (Whalen et al, 1999; Ross, 2003). Both serial counting and estimation change characteristics when the set of items is small–between 1 and 4 objects–a range known as subitizing (Kaufman et al, 1949). Subitizing has been reported for haptic spatial arrays, and for sequences of visual, and auditory stimuli
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
