It’s all relative: The role of object weight in toddlers’ gravity bias

Abstract

Work over the past 20 years has demonstrated a gravity bias in toddlers; when an object is dropped into a curved tube, they will frequently search at a point immediately beneath the entry of the tube rather than in the object's actual location. The current study tested 2- to 3½-year-olds' (N = 88) gravity bias under consideration of object weight. They were tested with either a heavy or light ball, and they had information about either one of the balls only or both balls. Evaluating their first search behavior showed that participants generally displayed the same age trends as other studies had demonstrated, with older toddlers passing more advanced task levels by being able to locate objects in the correct location. Object weight appeared to have no particular impact on the direction of these trends. However, where weight was accessible as relative information, toddlers were younger at passing levels and older at failing levels, although significantly so only from around 3 years of age onward. When they failed levels, toddlers made significantly more gravity errors with the heavy ball when they had information about both balls and made more correct choices with the light ball. As a whole, the findings suggest that nonvisual object variables, such as weight, affect young children's search behaviors in the gravity task, but only if these variables are presented in relation to other objects. This relational information has the potential to enhance or diminish the gravity bias.

Representational momentum in displacement tasks: Relative object weight matters in toddlers’ search behavior

“…In summary, it can be noted that object weight alone is not sufficient to impact their search behavior. As in other studies that relied on non-relational object variable comparisons in hidden displacement tasks, such as size (Gresham, 2012) and weight (Hast, 2018), the present study revealed no differences in performance between the two non-relational conditions.…”

“…However, toddlers had only been given opportunity to explore and see one of the two balls. This seems to be in accordance with Hast’s (2018) observation that object variables might only have an impact on search behavior when children are provided with opportunities for direct experience of contrasting examples of a variable, such as heaviness and lightness.…”

“…Young toddlers frequently select this location. However, while this behavior typically decreases with increasing age, recent research evaluating the particular role of relative object weight in this task revealed two main observations about 2- to 3½-year-olds (Hast, 2018). Relative heaviness of a test ball, prompted through having experienced the test ball and a lighter non-test ball, generally led toddlers to make the most gravity errors, and those toddlers who had been prompted with relative lightness made the most correct searches.…”

“…Specifically, Hast (2018) pointed out that a further bias in motion predictions, representational momentum (RM), might help in the interpretation of the findings. RM results in a tendency to believe that objects, based on their initial motion patterns, have traveled farther in the direction of motion than they actually have, and therefore there is a tendency to judge their final location as being farther along that trajectory (Freyd & Finke, 1984; for reviews see e.g., Hubbard, 2005, 2010, 2014).…”

“…First, if toddlers are given opportunity to manually experience weight of different objects, what role does knowledge of that relative weight play in their search behavior in RM-related search tasks? Based on Hast’s (2018) findings, it was hypothesized that relative heaviness would be more likely to lead to RM-related search errors and relative lightness to fewer errors. Second, what is the extent of impact—as measured by the disparity between actual and search location—that relative weight has on RM-related search behavior?…”