Summary accuracy feedback and the left digit effect in number line estimation

Abstract

A robust left digit effect arises in number line estimation such that adults’ estimates for numerals with different hundreds place digits but nearly identical magnitudes are systematically different from one another (e.g., 299 is placed too far to the left of 302). In two experiments, we investigate whether brief feedback interventions designed to increase task effort can reduce or eliminate the left digit effect in a self-paced 0–1,000 number line estimation task. Participants were assigned to complete three blocks of 120 trials each where the middle block contained feedback or no feedback. Feedback was in the form of summary accuracy scores (Experiment 1 ; N = 153) or competitive (summary) accuracy scores (Experiment 2 ; N = 145). In both experiments, planned analyses revealed large left digit effects in all blocks regardless of feedback condition. Feedback did not lead to a reduction in the left digit effect in either experiment, but improvements in overall accuracy were observed. We conclude that there are no changes in the left digit effect resulting from either summary accuracy feedback or competitive accuracy feedback. Also reported are exploratory analyses of trial characteristics (e.g., whether 299 is presented before or after 302) and the left digit effect. Supplementary Information The online version contains supplementary material available at 10.3758/s13421-022-01278-2.

Potential moderators of the left digit effect in numerical estimation

“…We also considered the alternative possibility that, following corrective feedback, the left digit effect remains unchanged. Such a finding would be consistent with Kayton et al (2022), in which summary accuracy feedback did not reduce the effect. The finding would provide evidence of the robustness of the left digit effect in NLE across feedback contexts and would support the possibility that the effect is not easily corrected through brief interventions.…”

“…This outcome would provide evidence of the robustness of the left digit effect in NLE across typical and atypical contexts. It would also be consistent with one cognitive account of the left digit effect suggesting that the overweighting of leftmost digits occurs in the conversion of symbols to magnitudes rather than being dependent on response format (see Thomas & Morwitz, 2005; see also Kayton et al, 2022, for a discussion).…”

“…This question speaks to the malleability of the left digit effect and whether it is relatively immutable or the result of a bias that is easily corrected. Kayton et al (2022) showed that summary feedback used to enhance motivation did not reduce the left digit effect. But, because that feedback was a summary score across trials, it could not easily be used to assess how to change one's placements for individual target numerals.…”

“…In much of the work to date, the overall magnitude of a target numeral is thought to guide participants' placements of numbers on a number line (e.g., 398 and 401 are predicted to be placed in similar locations on a 0-1000 line given their similar overall magnitudes). However, there is strong evidence that the individual digits comprising target numerals also influence bounded number line estimates (Kayton et al, 2022;Lai et al, 2018;Patalano et al, 2023;Savelkouls et al, 2020;Williams et al, 2022). For example, Lai et al (2018) observed a strong influence of leftmost digits on estimates of three-digit numbers with similar magnitudes but different leftmost hundreds-place digits, and there were large effect sizes at all ages tested.…”

“…The effect arises on speeded computer-based tasks (Lai et al, 2018) and persists when numbers around boundary values (the numbers commonly used to assess left digit effects, e.g., 798 and 802) are embedded in a more extensive stimulus set (Williams et al, 2020). Additionally, the effect remains even with instructional interventions designed to increase task effort through competitive summary feedback (presented using a game format; Kayton et al, 2022), suggesting that the effect is unlikely due to a lack of motivation or insufficient task effort alone, although further work is needed.…”