Against this, the present study reveals that visual enumeration is actually more accurate and more precise when the visual items are distributed between the left and right visual fields as when they are all presented within a single hemifield.
To control for the possibility that the bees could be using cues such as the edge lengths or combined areas of the visual items, we presented them with stimuli where these cues, in the sample and choice patterns, had been equalised.
We found that enumerating large number (>4 items), but not small number (<4 items), exhibited the bilateral field advantage: enumeration was more accurate when the visual items were split between the left and right hemifields than when they were all presented within the same hemifield.
Owing to the sensitivity of pupillary responses to light intensity (Cheng et al., 2006), as well as to chromatic changes (Tsujimura et al., 2006), stimulus properties such as ambient light, brightness, contrast, and the color of the presented visual items were controlled (for further details regarding the development and standardization of these stimuli, see Kafkas and Montaldi, 2011).
The ticked values for the two visual items were added and divided by two.
In the present study, the effect of distributing visual items across the two hemifields on visual enumeration was directly tested by pitting the unilateral and bilateral field advantage hypotheses against each other.
One explanation for our observation of a large Aud:Vis reactivation effect in the pSTS is that the during recognition memory of a congruent, but cross-modal, test-probe stimulus pair, the pSTS is engaged in a multisensory integration of the current visual item with the previously presented auditory item.
To this end, we used a visual enumeration task a task that requires the assimilation of separate visual items into a single quantity where the to-be-enumerated items were either presented in one hemifield or distributed between the two visual fields.
The threat questions asked about visual items such as the weapons, auditory items such as verbal threats and spatial items such as the proximity of the shooter to the officers.
When individuals are asked to determine the numbers of briefly presented visual items, differences in the slope accuracy are typically found between small versus large numbers [1], [2].
By limiting the stimulus presentation time, we can determine the maximum number of visual items an observer can correctly enumerate at a criterion level of performance (counting threshold, defined as the number of visual items at which ≈63% correct rate on a psychometric curve), without confounding by eye movements.
