Number and Continuous Magnitude Processing Depends on Task Goals and Numerosity Ratio

Abstract

A large body of evidence shows that when comparing non-symbolic numerosities, performance is influenced by irrelevant continuous magnitudes, such as total surface area, density, etc. In the current work, we ask whether the weights given to numerosity and continuous magnitudes are modulated by top-down and bottom-up factors. With that aim in mind, we asked adult participants to compare two groups of dots. To manipulate task demands, participants reported after every trial either (1) how accurate their response was (emphasizing accuracy) or (2) how fast their response was (emphasizing speed). To manipulate bottom-up factors, the stimuli were presented for 50 ms, 100 ms or 200 ms. Our results revealed (a) that the weights given to numerosity and continuous magnitude ratios were affected by the interaction of top-down and bottom-up manipulations and (b) that under some conditions, using numerosity ratio can reduce efficiency. Accordingly, we suggest that processing magnitudes is not rigid and static but a flexible and adaptive process that allows us to deal with the ever-changing demands of the environment. We also argue that there is not just one answer to the question ‘what do we process when we process magnitudes?’, and future studies should take this flexibility under consideration.

The interplay between non-symbolic number and its continuous visual properties revisited: Effects of mixing trials of different types

“…In terms of sensory integration theory, this finding can be interpreted as an increase in weights given to the continuous magnitudes. Thus, our results add to the growing body of evidence suggesting that these weights are dynamic and applied in an adaptive and flexible way (Leibovich et al, 2015, 2017; Leibovich, Kallai, & Itamar, 2016; Leibovich-Raveh et al, 2018). As mentioned before, different instructions, task difficulty, exposure duration, and task context can alter the effect of continuous magnitudes on dot comparison performance.…”

“…Further studies, which address the role of continuous magnitudes on numerosity processing, may add to our understanding about the interplay between discrete numerosity and continuous sensory cues. For example, it has been shown that the effect of continuous magnitudes on dot comparison performance can be altered by changes in instructions, task difficulty, stimulus duration, and task context (Leibovich et al, 2015; Leibovich-Raveh et al, 2018). Thus, the weights that are given to continuous magnitudes are not static but seem to depend on various experimental factors.…”

“…In another block, it was the opposite: The convex hull of stimulus pairs was manipulated in the same way (congruent or incongruent), whereas the dot diameter remained constant. But, assuming that the weighing process is flexible and adaptive as suggested by Leibovich et al and also that trial history has an effect on dot comparison performance as suggested by Odic et al, it is possible that the blocked presentation mode influences the weights given to the continuous magnitudes in a particular way (Leibovich et al, 2015; Leibovich-Raveh et al, 2018; Odic et al, 2014). For example, if during the entire block the two stimuli in a trial differ with regard to convex hull, whereas the other continuous cues are kept constant, the weight assigned to the convex hull may increase or decrease compared with the weights of other continuous magnitudes.…”

Magnitude integration in the Archerfish

“…The current study took this question one step forward by not only asking whether non-numerical magnitudes influence performance or not, but showing that (1) this influence, in an untrained animal, is moderated by the number of non-numerical magnitudes positively correlated with numerical quantity, and (2), that the number of non-numerical magnitudes, not their identity, influence performance. Since this is the first attempt to ask these questions in an untrained animal, and since it is well-known that the way the stimuli are built can greatly impact performance e.g., 32 , 36 , replication studies with the same and different stimuli that were composed in different ways are necessary to confirm or restrict the results and conclusions of the current study. We hope that this work will inspire similar research with different animals and different types of stimuli.…”

“…In addition, it also allows expanding the context of the task. Namely, magnitude discrimination, at least in humans, is context-dependent e.g., 32 , 33 . Given the multiple tasks magnitude discrimination may be required for (hunting, mate selection, avoiding predators, shelter-seeking), it is possible that for different tasks, different magnitudes will guide an animal’s decision.…”