Coding of featural information in visual working memory in 2.5-year-old toddlers

An object's categorizability impacts whether infants encode surface features into their object representations

Infants encode the surface features of simple, unfamiliar objects (e.g., red triangle) and the categorical identities of familiar, categorizable objects (e.g., car) into their representations of these objects. We asked whether 16-18-month-olds ignore non-diagnostic surface features (e.g., color) in favor of encoding an object's categorical identity (e.g., car) when objects are from familiar categories. In Experiment 1 (n = 18), we hid a categorizable object inside an opaque box. In No Switch trials, infants retrieved the object that was hidden. In Switch trials, infants retrieved a different object: an object from a different category (Between-Category-Switch trials) or a different object from the same category (Within-Category-Switch trials). We measured infants' subsequent searching in the box. Infants' pattern of searching suggested that only infants who completed a Within-Category-Switch trial as their first Switch trial encoded objects' surface features, and an exploratory analysis suggested that infants who completed a Between-Category-Switch trial as their first Switch trial only encoded objects' categories. In Experiment 2 (n = 18), we confirmed that these results were due to objects' categorizability. These results suggest infants may tailor the way they encode categorizable objects depending on which object dimensions are perceived to be task relevant.

Tracking what went where across toddlerhood: Feature-location bound object representations in 2- to 3-year-olds' working memory

Two experiments examined the development of the ability to encode, maintain, and update integrated representations of occluded objects' locations and featural identities in working memory across toddlerhood. Sixty-eight 28- to 40-month-old US toddlers (13 Asian or Pacific Islander, 6 Black, 48 White, 1 multiracial; 40 girls; tested between February 2015 and July 2017) tracked the locations of different color beads that were hidden simultaneously (Experiment 1) or sequentially (Experiment 2). Toddlers' ability to reliably store feature-location bound object representations in working memory varied as a function of age, memory load, and task demands. These results bridge a developmental gap between infancy and early childhood and provide new insights into sources of limitation and developmental change in children's early object representational capacities.

Two-year-olds use past memories to accomplish novel goals

Memory-guided planning involves retrieving relevant memories and applying that information in service of a goal. Previous studies have shown substantial development in this ability from 3 to 4 years of age. We investigated the emergence of memory-guided planning by asking whether 2-year-olds could draw on episodic memories of past experiences to generate and execute plans. In Experiments 1 and 2 (N = 32, ds > .7), 2-year-olds successfully did so, and this ability developed significantly across the third year of life. Furthermore, in Experiment 3 (N = 19, d = 0.63), 2-year-olds successfully applied episodic memories to guide plans in a novel problem context, suggesting flexibility in this ability. Together, these results suggest that some form of memory-guided planning emerges during the third year of life and may form the cognitive basis for episodic prospection later in development.

A working memory span task for toddlers

This study presents a new working memory measure for toddlers, inspired by the Spin-the-Pots (Hughes & Ensor, 2005), which we modified structuring it as a memory span task. As in the original task, we required toddlers to retrieve objects hidden in little boxes; however, in our Memory Span Spin-the-Pots (MSSP) we used smaller numbers of targets, and we systematically manipulated memory load, covering or not the display, and rotating it or not. Two experiments involved participants between 18 months and three years. In Experiment 1 we examined the effects of covering and rotation on toddlers' memory. Either covering or rotating the stimuli hindered their performance, and combining both transformations yielded an under-additive interaction. Moreover, the effect of covering decreased in the second half of the procedure. In Experiment 2 we validated the MSSP as a working memory measure by comparing it with the Imitation Sorting Task (IST; Alp, 1994). We found that the MSSP correlated with the IST, also with age partialled out, although the IST was easier. In both experiments, the scores increased with age. Overall, this research sheds light on some variables that affect toddlers' performance on the MSSP, and shows that it can be used as a valid working memory measure for toddlers. The results are discussed considering the attentional processes presumably involved.