Connecting the Dots Between Past and Future: Constraints in Episodic Future Thinking in Early Childhood

Of popsicles and crackers: when spatio-temporal memory is not integrated into children's decision-making

Prior research has used innovative paradigms to show that some non-human animal species demonstrate behavioural choices (i.e. foraging for a food item at a specific location, and at a time that guarantees it has not yet decayed), reflecting episodic-like or 'WWW' memory (memory for 'what' happened, 'where' and 'when'). These results raised the question of whether similar approaches could be used to examine memory in young children in order to reduce verbal demands. The present research examines the extent to which children's WWW memory aligns with memory-based choices in 3- to 5-year-olds (n = 95; study 1) and in 7- to 11-year-olds and adults (n = 168; study 2). Results indicate that preschoolers' struggle with choice-based tasks probably reflects difficulty integrating their WWW memory with an understanding that certain items decay over time. Moreover, a convergence between verbal recall measures and choice-based measures is observable in 7-year-olds and beyond, reflecting a stronger integration of memory signals, understanding of state transformation, and decision-making. This article is part of the theme issue 'Elements of episodic memory: lessons from 40 years of research'.

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.

"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.

Back to the future: relating the development of episodic future thinking to cognitive and affective individual differences and to motivational relevance in preschoolers

Episodic future thinking (EFT) represents the ability to mentally simulate scenarios that will occur in our personal future. In the current study, we used the item choice paradigm, which puts chidren in a problematic situation and requires them to envision a solution by selecting one of various items. This ability was assessed in a sample of 92 preschoolers (3-6 years old), taking into account individual differences in age, gender, cognitive (verbal abilities, EFT memory) and affective (anxiety) factors, as well as contextual factors (motivational relevance). Findings indicate developmental progress in preschoolers' foresight and in their retrospective memory for the item choice problems. The motivational valence of the EFT task played a significant role, as children performed better in the motivationally positive condition, as compared to the neutral and negative ones. However, older children had better performance than younger ones on the motivationally aversive tasks, becoming comparable to their performance in the motivationally appetitive condition. Finally, higher social anxiety was negatively related to children's EFT performance in the aversive condition, when they anticipated negative social exposure. In conclusion, EFT was explained by age-related improvements, the motivational valence of the situation and by individual differences in social anxiety, which is highly relevant for educational and therapeutic practices.

Memory-related hippocampal activation during sleep and temporal memory in toddlers

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Two-year-olds played tablet games requiring them to remember locations visited by characters and the temporal order with which they visited them.

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Two-year-olds remembered spatial locations better than temporal order immediately after learning, and after a 20-minute and one-week delay.

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Song-related hippocampal activation during sleep is associated with memory for temporal order.

Nonhuman research has implicated developmental processes within the hippocampus in the emergence and early development of episodic memory, but research in humans has been constrained by the difficulty of examining hippocampal function during early development. In the present study, we assessed 48 2-year-olds with a novel paradigm in which participants completed two games on a tablet that required remembering associations between unique characters, the places they visited, and the temporal order with which they did so. At the completion of each game, a unique, novel song played. Toddlers remembered spatial locations better than temporal order during an immediate test, after a 20-minute delay, and after a week delay. After the last behavioral session, toddlers underwent an fMRI task during natural nocturnal sleep evaluating hippocampal activation in response to learned and novel songs. We found that the extent of hippocampal activation for learned songs compared to novel songs during sleep was correlated with memory for temproal order across all time delays, but not with memory for spatial locations. The results confirm that that the functional contribution of the hippocampus to early memory can be assessed during sleep and suggest that assessment of temporal aspects of memory in the current task best capture this contribution.

Updating and reasoning: Different processes, different models, different functions

Two issues should be addressed to refine and extend the distinction between temporal updating and reasoning advocated by Hoerl & McCormack. First, do the mental representations constructed during updating differ from those used for reasoning? Second, are updating and reasoning the only two processes relevant to temporal thinking? If not, is a dual-systems framework sensible? We address both issues below.