Haptic and Auditory Enumeration of the Contents of a Container

Everyday experiences suggest that containers, such as a box of chocolate sprinkles, can convey pertinent information about the nature of its content. Despite the familiarity of the experience, we do not know which sources of information people use to estimate the number of objects in a container and which enumeration processes (subitizing, counting, estimation) come into play. The current study explores the impact of auditory and haptic cues on enumeration as well as the transition points between the enumeration processes. In two experiments, we investigated exploration times and accuracy of enumeration of boxes containing 1-8 items under three conditions: auditory-only, haptic-only and combined haptic-auditory cues. In the first experiment, participants explored the boxes for 5 seconds. In the second experiment, participants were free to explore, and we recorded exploration times. The auditory-only condition yielded the highest accuracy, the haptic-only condition the lowest accuracy, while the haptic-auditory condition fell in the middle range, suggesting a weighted average of both sensory modalities. The subitizing range was ~3 items for auditory and haptic-auditory modalities and ~2 items for the haptic-only condition. Larger numbers were enumerated less accurately and yielded similar exploration times: we therefore conclude that larger numbers are estimated and not counted.