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

Abstract

In the last few years, the existence of a pure number sense has been challenged. Recent studies suggest that numerosity processing is influenced not only by the number of elements in a display but also by continuous magnitudes, such as the size of the elements. The aim of our study was to replicate and extend the findings by Gebuis and Reynvoet, who systematically manipulated different continuous magnitudes either congruently or incongruently with discrete numerosity. We were particularly interested in finding the same pattern of congruency effects and assess its stability and robustness as this pattern indicates a complex influence of continuous magnitudes on numerosity judgements. We did so by showing stimuli of different conditions either in separate blocks or mixed together while participants solved a dot comparison task. Our results are in line with the notion that discrete number and continuous magnitudes are integrated in numerosity judgements by means of a weighing process. Moreover, our findings suggest that this integration is modified by the mode of presentation (blocked vs. mixed).

Over- and Underweighting of Extreme Values in Decisions from Sequential Samples

“…This observation is consistent with the results from our model simulations, which assume an upper bound on the gain of processing available to an observer on any given trial (Li et al, 2017;Spitzer et al, 2017). It remains to be shown whether our experimental results with symbolic numbers will generalize to other input formats (e.g., using analogue sensory continua; Liu et al, 2015;Marinova et al, 2020;Pekár & Kinder, 2019;Rosenbaum et al, 2021;, where the distribution and range of input values may play an additional role. For instance, while the discrete numerical samples in our experiment were easily readable (i.e., early sensory noise was presumably negligible), other sensory-perceptual inputs may be more prone to, e.g., range adaptation effects (Brenner et al, 2000;Fairhall et al, 2001;Smirnakis et al, 1997;Wark et al, 2007), which might also impact the shape of psychometric weighting.…”

Representation of visual numerosity information during working memory in humans: An fMRI decoding study

“…A challenge for the design of visual dot numerosity stimuli is that one cannot change the numerosity and hold all other stimulus' parameters constant. As a consequence, stimuli can contain sensory cues, which are physical stimulus properties that are nonnumerical, such as total surface area or dot diameter (Gebuis et al, 2016; Pekár & Kinder, 2019; Piazza et al, 2004; Salti et al, 2017). The dot position in our stimuli was chosen randomly, which does not exclude minor differences in the convex hull, namely the area within a stimulus covered with dots.…”

“…To ensure that participants draw on the approximation of numerosity, as opposed to counting or other strategies, some conceptual distinctions are made. First, humans can process numerosity in two different formats: symbolic (e.g., Arabic numbers) and nonsymbolic, the latter requires an estimation of the numerosity through the ANS (Gebuis & Reynvoet, 2012; Pekár & Kinder, 2019). Furthermore, in order to investigate number estimation, it has to be ensured that participants do not use subitizing, which is the almost immediate, precise, and effortless (i.e., without counting) recognition of set sizes of up to 4–5 items (Cohen & Henik, 2016; Kaufman, Lord, Reese, & Volkmann, 1949; Trick & Pylyshyn, 1994).…”

“…As the numerosity of a stimulus is often linked to physical stimulus properties, it is likely that such codes reflect differences in low‐level stimulus properties (Gebuis et al, 2016). The difficulty is to dissociate low‐level stimulus features from a stimulus' numerosity, which requires careful stimulus and trial design (Gebuis & Reynvoet, 2011; Pekár & Kinder, 2019; Piazza et al, 2004; Salti, Katzin, Katzin, Leibovich, & Henik, 2017).…”

Video playback versus live stimuli to assess quantity discrimination in angelfish (Pterophyllum scalare)

“…This aspect may create experimental error variation, and thus may reduce statistical power and reproducibility of results (Chouinard-Thuly et al, 2017 ; Gerlai, 2017 ; Gerlai, 2019 ). Furthermore, precise parametric control of most features of the live stimulus fish is impossible (e.g., see Gebuis & Reynvoet, 2012 ; Pekár & Kinder, 2020 ), and thus systematic analysis of the potential effects of such factors is difficult. A powerful, yet simple, method with which these issues may be addressed is the presentation of video-recordings.…”