"Shape bias" goes social: Children categorize people by weight rather than race.

Children tend to categorize novel objects according to their shape rather than their color, texture, or other salient properties-known as "shape bias." We investigated whether this bias also extends to the social domain, where it should lead children to categorize people according to their weight (their body shape) rather than their race (their skin color). In Study 1, participants (n = 50 US 4- and 5-year-olds) were asked to extend a novel label from a target object/person to either an object/person who shared the target's shape/weight, color/race, or neither. Children selected the shape-/weight-matched individual over the color-/race-matched individual (dobjects  = 1.58, dpeople  = 0.99) and their shape biases were correlated across the two domains. In Study 2, participants (n = 20 US 4- and 5-year-olds) were asked to extend a novel internal property from a target person to either a person who shared the target's weight, race, or neither. Again, children selected the weight-matched individual (d = 1.98), suggesting they view an individual's weight as more predictive of their internal properties than their race. Overall, results suggest that children's early shape bias extends into the social domain. Implications for weight bias and early social cognition are discussed. RESEARCH HIGHLIGHTS: Preschoolers extend novel labels based on people's weight rather than their race. Preschoolers infer internal features based on people's weight rather than their race. Shape biases are present, and correlated, across the social and object domains.

"Catastrophic" set size limits on infants' capacity to represent objects: A systematic review and Bayesian meta-analysis.

Decades of research has revealed that humans can concurrently represent small quantities of three-dimensional objects as those objects move through space or into occlusion. For infants (but not older children or adults), this ability apparently comes with a significant limitation: when the number of occluded objects exceeds three, infants experience what has been characterized as a "catastrophic" set size limit, failing to represent even the approximate quantity of the hidden array. Infants' apparent catastrophic representational failures suggest a significant information processing limitation in the first years of life, and the evidence has been used as support for prominent theories of the development of object and numerical cognition. However, the evidence for catastrophic failure consists of individual small-n experiments that use null hypothesis significance testing to obtain null results (i.e., p > 0.05). Whether catastrophic representational failures are robust or reliable across studies, methods, and labs is not known. Here we report a systematic review and Bayesian meta-analysis to examine the strength of the evidence in favor of catastrophic representational failures in infancy. Our analysis of 22 experiments across 12 reports, with a combined total of n = 367 infants aged 10-20 months, revealed strong support for the evidence for catastrophic set size limits. A complementary analysis found moderate support for infants' success when representing fewer than four objects. We discuss the implications of our findings for theories of object and numerical cognitive development. RESEARCH HIGHLIGHTS: Previous work has suggested that infants are unable to concurrently represent four or more objects-a "catastrophic" set size limit. We reviewed this work and conducted a Bayesian meta-analysis to examine the robustness of this limit across individual small-n experiments. We found strong support for the evidence for catastrophic set size limits, and moderate support for infants' success when representing fewer than four objects.

Children's use of reasoning by exclusion to infer objects' identities in working memory.

Reasoning by exclusion allows us to form more complete representations of our environments, "filling in" inaccessible information by ruling out known alternatives. In two experiments (Experiment 1: N = 34 4- to 6-year-olds; Experiment 2: N = 85 4- to 8-year-olds), we examined children's ability to use reasoning by exclusion to infer the identity of an unknown object and investigated the role of working memory in this ability. Children were asked to encode a set of objects that were then hidden, and after a brief retention interval children were asked to select the identity of the object hidden in one of the locations from two alternatives. On some trials, all the images were visible during encoding, so selecting the correct identity when probed required successful working memory storage and retrieval. On other trials, all but one of the images was visible during encoding, so selecting the correct identity when probed also required maintaining a representation of an unknown object in working memory and then using reasoning by exclusion to fill in the missing information retroactively to complete that representation by ruling out known alternatives. To investigate the working memory cost of exclusive reasoning, we manipulated the working memory demands of the task. Our results suggest that children can use reasoning by exclusion to retroactively assign an identity to an incomplete object representation at least by 4 years of age but that this ability incurs some cognitive cost, which eases with development. These results provide new insights into children's representational capacities and on the foundational building blocks of fully developed exclusive reasoning.

Three- and four-year-old children represent mutually exclusive possible identities.

How do children think about and plan for possible outcomes of events that could happen in the future? Previous work that has investigated children's ability to think about mutually exclusive possibilities has largely focused on children's reasoning about one type of possibility-the possible locations of an object. Here, we investigated children's reasoning about another type of possibility-mutually exclusive possible identities. In two experiments (N = 201 U.S. 3- and 4-year-olds), children were told that two animal characters (e.g., a bunny and a monkey) were going to take turns sliding down a playground slide. Children were told that the animals wanted to eat their favorite foods (e.g., carrots and bananas, respectively) as soon as they got to the bottom of the slide. In an Unambiguous Identity condition, we told children the identity of the animal that would slide down. In an Ambiguous Identity condition, we told children that which animal would slide down first was unknown. To examine children's representations of possible identities, we asked children to "get snack ready." We found that children in the Unambiguous Identity condition selected only one of the snacks (i.e., the favorite snack of the animal they were told would slide down), whereas children in the Ambiguous Identity condition selected both snacks, suggesting that they were accounting for both possible identities. These results extend the literature on the development of modal reasoning to include reasoning about possible identities and suggest that this ability may be available to children as young as 3 years.

"Plan chunking" expands 3-year-olds' ability to complete multiple-step plans.

The ability to use knowledge to guide the completion of goals is a critical cognitive skill, but 3-year-olds struggle to complete goals that require multiple steps. This study asked whether 3-year-olds could benefit from "plan chunking" to complete multistep goals. Thirty-two U.S. children (range = 35.75-46.59 months; 18 girls; 9 white, 3 mixed race, 20 unknown; tested between July 2020 and April 2021) were asked to complete "treasure maps," retrieving four colored map pieces by pressing specific buttons on a "rainbow box." Children completed more of the four-step sequence correctly when the steps were presented in a way that encouraged chunking the steps into pairs. These findings suggest a potential mechanism supporting memory-guided planning abilities in early childhood.

Explore versus store: Children strategically trade off reliance on exploration versus working memory during a complex task.

During complex tasks, we use working memory to actively maintain goal sets and direct attention toward goal-relevant information in the environment. However, working memory is severely limited, and storing information in working memory is cognitively effortful. Previous work by Kibbe and Kowler [2011, Journal of Vision, 11(3), Article 14] showed that adults strategically modulate reliance on working memory during complex, goal-oriented tasks, varying the amount of information they store in working memory depending both on the cognitive demands of the task and on the ease with which task-relevant information can be accessed from the environment. We asked whether children, whose working memory and executive functions are undergoing significant developmental change, also use working memory strategically during complex tasks. Forty-six 8-10-year-old children searched through arrays of hidden objects to find three that belonged to a given category defined over the objects' features. We manipulated the cognitive demands of the task by increasing the complexity of the category. We manipulated the exploration costs of the task by varying the rate at which task-relevant information could be accessed. We measured children's search patterns to gain insights into how the children used working memory during the task. We found that as the cognitive demands of the task increased, children stored less information in working memory, relying more on exploration. When exploration was costlier, children explored less, storing more in working memory. These results suggest that developing children, like adults, make strategic decisions about when to explore versus when to store during a complex, goal-oriented task.

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.

The language-of-thought as a working hypothesis for developmental cognitive science.

A science of prelinguistic infant cognition must take seriously the language-of-thought (LoT) hypothesis. I show how the LoT framework enables us to identify the representational and computational capacities of infant minds and the developmental factors that act on these capacities, and explain how Quilty-Dunn et al.'s take on LoT has important upshots for developmental theory-building.

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.

Altruistic self-regulation in young children.

We investigated whether children would be willing to sustain delaying their own gratification in order to benefit someone else. We used a modified version of the classic "marshmallow task," in which children must sustain delaying gratification in the presence of the immediate reward for an unspecified amount of time in order to receive a larger reward later. Children were assigned to one of three conditions. In the Self condition, children were given a food item and were told that if they waited to eat it, they would receive a second food item. In the Prosocial condition, children also were given a food item but were told that if they waited to eat their food item, another child would get a food item. In the Nonsocial Control condition, children were given a food item but were told that waiting to eat it would not benefit anyone. We found that children waited significantly longer in both the Self and Prosocial conditions than in the Nonsocial Control condition, and children's wait durations in the Self and Prosocial conditions were not significantly different. Our results suggest that children are willing to engage in effortful self-regulation in order to benefit another child.

Conceptually Rich, Perceptually Sparse: Object Representations in 6-Month-Old Infants' Working Memory.

Six-month-old infants can store representations of multiple objects in working memory but do not always remember the objects' features (e.g., shape). Here, we asked whether infants' object representations (a) may contain conceptual content and (b) may contain this content even if perceptual features are forgotten. We hid two conceptually distinct objects (a humanlike doll and a nonhuman ball) one at a time in two separate locations and then tested infants' memory for the first-hidden object by revealing either the original hidden object or an unexpected other object. Using looking time, we found that infants remembered the categorical identity of the hidden object but failed to remember its perceptual identity. Our results suggest that young infants may encode conceptual category in a representation of an occluded object, even when perceptual features are lost.

A systematic assessment of socioeconomic status and executive functioning in early childhood.

Lower socioeconomic status (SES) consistently relates to poorer executive function (EF). This study used a systematic and nuanced approach to understand how SES relates to children's EF at a process level. We assessed children aged 4.5-5.5 years. This is a key developmental period because EF is no longer a unitary construct but rather EF components statistically load on separate factors and index distinct aspects of EF. Children completed a working memory task that involved a cognitive load component and a go/no-go task to assess inhibitory control and vigilance. Accuracy and reaction time were assessed, and each task involved four blocks to assess performance over time. Lower SES related to lower accuracy for working memory, inhibitory control, and vigilance as well as slower reaction time for working memory. SES did not relate to go/no-go reaction time. For working memory, lower SES related to poorer accuracy on lower cognitive load trials, but there were no SES differences on higher cognitive load trials. SES did not relate to maintenance of performance over time. Results suggest that for this age group the majority of domains showed SES differences. However, there were no SES differences in performance for remembering two items and maintaining performance. Thus, although overall lower SES related to poorer EF performance, there were no SES effects for skills that are still emerging for all children, namely, maintaining task performance across time and remembering two items at once. Results highlight the importance of assessing EF as a multidimensional construct and may help to identify targets for intervention.

Six-Month-Old Infants Predict Agents' Goal-Directed Actions on Occluded Objects.

Infants can infer agents' goals after observing agents' goal-directed actions on objects and can subsequently make predictions about how agents will act on objects in the future. We investigated the representations supporting these predictions. We familiarized 6-month-old infants to an agent who preferentially reached for one of two featurally distinct objects following a cue. At test, the objects were sequentially occluded from the infant in the agent's presence. We asked whether infants could generate action predictions without visual access to the relevant objects by measuring whether infants shifted their gaze to the location of the agent's hidden goal object following the cue. We also examined what infants represented about the hidden objects by removing one of the occluders to reveal either the original hidden object or the unexpected other object and measuring infants' looking time. We found that, even without visual access to the objects, infants made predictive gazes to the location of the agent's occluded goal object, but failed to represent the features of either hidden object. These results suggest that infants make goal-based action predictions when the relevant objects in the scene are occluded, but doing so may come at the expense of maintaining representations of the objects.

Examining the limits of Memory-Guided Planning in 3- and 4-year olds.

Stored memories may be drawn upon when accomplishing goals. In two experiments, we investigated limits on the ability to use episodic memories to support planning in 3- and 4-year-old children. We designed a new memory-guided planning task that required children to both retrieve memories and apply those memories to accomplish multiple, nested goals. We manipulated the difficulty of the task by varying the number of steps required to achieve the goals, and examined the impact of this manipulation on both memory retrieval and planning. We found that, overall, 4-year-olds outperformed 3-year-olds, but as task difficulty increased, all children made more errors. Analysis of these errors suggested that retrieval and planning processes might impose separate limits on memory-guided planning in early childhood, but that these limits may ease across early childhood.

Visual Memories Bypass Normalization.

How distinct are visual memory representations from visual perception? Although evidence suggests that briefly remembered stimuli are represented within early visual cortices, the degree to which these memory traces resemble true visual representations remains something of a mystery. Here, we tested whether both visual memory and perception succumb to a seemingly ubiquitous neural computation: normalization. Observers were asked to remember the contrast of visual stimuli, which were pitted against each other to promote normalization either in perception or in visual memory. Our results revealed robust normalization between visual representations in perception, yet no signature of normalization occurring between working memory stores-neither between representations in memory nor between memory representations and visual inputs. These results provide unique insight into the nature of visual memory representations, illustrating that visual memory representations follow a different set of computational rules, bypassing normalization, a canonical visual computation.

Young children 'solve for x' using the Approximate Number System.

The Approximate Number System (ANS) supports basic arithmetic computation in early childhood, but it is unclear whether the ANS also supports the more complex computations introduced later in formal education. 'Solving for x' in addend-unknown problems is notoriously difficult for children, who often struggle with these types of problems well into high school. Here we asked whether 4-6-year-old children could solve for an unknown addend using the ANS. We presented problems either symbolically, using Arabic numerals or verbal number words, or non-symbolically, using collections of objects while preventing verbal counting. Across five experiments, children failed to identify the value of the unknown addend when problems were presented symbolically, but succeeded when problems were presented non-symbolically. Our results suggest that, well before formal exposure to unknown-addend problems, children appear to 'solve for x' in an intuitive way, using the ANS.

Developmental origins of recoding and decoding in memory.

Working memory is severely limited in both adults and children, but one way that adults can overcome this limit is through the process of recoding. Recoding happens when representations of individual items are chunked together into a higher order representation, and the chunk is assigned a label. That label can then be decoded to retrieve the individual items from long-term memory. Whereas this ability has been extensively studied in adults (as, for example, in classic studies of memory in chess), little is known about recoding's developmental origins. Here we asked whether 2- to 3-year-old children also can recode-that is, can they restructure representations of individual objects into a higher order chunk, assign this new representation a verbal label, and then later decode the label to retrieve the represented individuals from memory. In Experiments 1 and 2, we showed children identical blocks that could be connected to make tools. Children learned a novel name for a tool that could be built from two blocks, and for a tool that could be built from three blocks. Later we told children that one of the tools was hidden in a box, with no visual information provided. Children were allowed to search the box and retrieve varying numbers of blocks. Critically, the retrieved blocks were identical and unconnected, so the only way children could know whether any blocks remained was by using the verbal label to recall how many objects comprised each tool (or chunk). We found that even children who could not yet count adjusted their searching of the box depending on the label they had heard. This suggests that they had recoded representations of individual blocks into higher-order chunks, attached labels to the chunks, and then later decoded the labels to infer how many blocks were hidden. In Experiments 3 and 4 we asked whether recoding also can expand the number of individual objects children could remember, as in the classic studies with adults. We found that when no information was provided to support recoding, children showed the standard failure to remember more than three hidden objects at once. But when provided recoding information, children successfully represented up to five individual objects in the box, thereby overcoming typical working memory limits. These results are the first demonstration of recoding by young children; we close by discussing their implications for understanding the structure of memory throughout the lifespan.

Three-year-olds' ability to plan for mutually exclusive future possibilities is limited primarily by their representations of possible plans, not possible events.

The ability to prepare for mutually exclusive possible events in the future is essential for everyday decision making. Previous studies have suggested that this ability develops between the ages of 3 and 5 years, and in young children is primarily limited by the ability to represent the set of possible outcomes of an event as "possible". We tested an alternative hypothesis that this ability may be limited by the ability to represent the set of possible actions that could be taken to prepare for those possible outcomes. We adapted the inverted y-shaped tube task of Redshaw and Suddendorf (2016), in which children are asked to catch a marble that is dropped into the top of the tube and can emerge from either the left or right branch of the tube. While 4-year-olds typically place their hands under both openings to catch the marble, preparing for both possible outcomes (optimal action), 3-year-olds often cover only one opening, preparing for only one possible outcome (suboptimal action). In three Experiments, we asked whether first showing children the set of possible actions that could be taken on the tube would enable them to recognize the optimal action that should be used to catch the marble (Experiments 1 and 3, total n = 99 US 3- and 4-year-olds) and enable them to use the optimal action themselves (Experiment 2, n = 96 US 3- and 4-year-olds). We found that 3- and 4-year-olds performed similarly when they were given the opportunity to observe the set of possible actions beforehand. These findings suggest that 3-year-olds' competence at representing mutually exclusive possibilities may be masked by their developing ability to represent and deploy plans to act on these possibilities.

What's the object of object working memory in infancy? Unraveling 'what' and 'how many'.

Infants have a bandwidth-limited object working memory (WM) that can both individuate and identify objects in a scene, (answering 'how many?' or 'what?', respectively). Studies of infants' WM for objects have typically looked for limits on either 'how many' or 'what', yielding different estimates of infant capacity. Infants can keep track of about three individuals (regardless of identity), but appear to be much more limited in the number of specific identities they can recall. Why are the limits on 'how many' and 'what' different? Are the limits entirely separate, do they interact, or are they simply two different aspects of the same underlying limit? We sought to unravel these limits in a series of experiments which tested 9- and 12-month-olds' WM for object identities under varying degrees of difficulty. In a violation-of-expectation looking-time task, we hid objects one at a time behind separate screens, and then probed infants' WM for the shape identity of the penultimate object in the sequence. We manipulated the difficulty of the task by varying both the number of objects in hiding locations and the number of means by which infants could detect a shape change to the probed object. We found that 9-month-olds' WM for identities was limited by the number of hiding locations: when the probed object was one of two objects hidden (one in each of two locations), 9-month-olds succeeded, and they did so even though they were given only one means to detect the change. However, when the probed object was one of three objects hidden (one in each of three locations), they failed, even when they were given two means to detect the shape change. Twelve-month-olds, by contrast, succeeded at the most difficult task level. Results show that WM for 'how many' and for 'what' are not entirely separate. Individuated objects are tracked relatively cheaply. Maintaining bindings between indexed objects and identifying featural information incurs a greater attentional/memory cost. This cost reduces with development. We conclude that infant WM supports a small number of featureless object representations that index the current locations of objects. These can have featural information bound to them, but only at substantial cost.