We appreciate Gilead et al.'s highlighting of the various “epistemic barriers” or “dimensions” (in addition to “time”) that humans must mentally traverse. Inherent to their theory of mental travel is that the different dimensions/distances (i.e., temporal, spatial, social, and hypotheticality) are intertwined, mostly interchangeable (thus lumped together under the broader construct of “mental travel”), and co-occurring in ontogeny. However, this characterization overlooks important nuances between different forms of mental travel and the diverse representational capacities subserving them. This is especially apparent in recent cognitive developmental data suggesting that children's sensitivity to different dimensions emerges in a staggered manner, and that the capacity to traverse dimensions may rely on different underlying representational capacities.
Developmental research has not yet provided a comprehensive account of when different forms of “mental travel” emerge and, importantly, whether sensitivity to each dimension emerges simultaneously. Yet, new data suggest important differences as a function of the dimension children must traverse. A notable point is that traversing social distance appears to emerge early in development. For example, taking a socially distanced perspective (by reasoning about “other” vs. “self”) enhances 3- to 5-year-olds' ability to predict future preferences (Bélanger et al. Reference Bélanger, Atance, Varghese, Nguyen and Vendetti2014; Lee & Atance Reference Lee and Atance2016) and delay gratification (Prencipe & Zelazo Reference Prencipe and Zelazo2005). Social distancing also improves executive functioning in this same age group. White and Carlson (Reference White and Carlson2016) found that preschoolers who took the perspective of another character (e.g., Batman) during an executive functioning task showed increased performance compared to preschoolers whose perspective was focused on the self. This effect was, however, more pronounced for 5- than 3-year-olds suggesting that even though young preschoolers are sensitive to social distance manipulations, this sensitivity increases with age.
Interestingly, however, preliminary work also suggests that children's sensitivity to spatial distance emerges later than sensitivity to social distance. For example, although taking a socially distanced perspective improved preschoolers' ability to predict future preferences (Bélanger et al. Reference Bélanger, Atance, Varghese, Nguyen and Vendetti2014) and delay gratification (Prencipe & Zelazo Reference Prencipe and Zelazo2005), Rutt et al. (Reference Rutt, O'Brien and Atance2019) recently showed that a spatial distance manipulation had no such facilitative effect. Specifically, 3- to 6-year-olds who were asked to take a spatially distanced perspective by imagining themselves in a far-away place were no more accurate in predicting future preferences, nor delaying gratification, than children who adopted a spatially near perspective (i.e., their current location). Similarly, Bowman-Smith et al. (Reference Bowman-Smith, Shtulman and Friedman2019) found that a spatial distance manipulation did not have a significant effect on children's reasoning until 6½. These findings, thus, suggest important differences between mental travel across social and spatial distances.
Findings by Coughlin et al. (Reference Coughlin, Robins and Ghetti2019) provide further evidence of differences between forms of mental travel. They compared 5-year-olds', 11-year-olds', and adults' ability to produce “temporal” and “make-believe” (i.e., hypothetical mental travel) narratives about a particular event (e.g., eating something yummy). Five- to 11-year-olds required more prompts to successfully produce future event narratives, and also received lower episodicity (i.e., amount of episodic detail) scores on future narratives, as compared to make-believe event narratives. Older children also required fewer prompts than younger children to produce future event narratives, whereas the number of prompts required for make-believe events did not differ with age. These findings suggest that the ability to mentally traverse time emerges later than the ability to mentally traverse hypotheticality.
Therefore, although we agree that different forms of mental travel might be largely interchangeable in adults, they appear to develop in a staggered manner in childhood. Though more data are needed, traversing (or being sensitive to) social (Bélanger et al. Reference Bélanger, Atance, Varghese, Nguyen and Vendetti2014; Lee & Atance Reference Lee and Atance2016) and hypothetical distances (Coughlin et al. Reference Coughlin, Robins and Ghetti2019) appear to emerge earlier in development than traversing temporal (Coughlin et al. Reference Coughlin, Robins and Ghetti2019) and spatial distances (Bowman-Smith et al. Reference Bowman-Smith, Shtulman and Friedman2019; Rutt et al. Reference Rutt, O'Brien and Atance2019).
In light of this, it is unsurprising that the mental representations (or forms of “abstraction”) subserving the various dimensions of mental travel also appear to differ. For example, as described earlier, Coughlin et al. (Reference Coughlin, Robins and Ghetti2019) found that young children were better able to episodically pre-experience a hypothetical, than a future, event even though both dimensions require event simulation. Importantly, these authors found that self-concept coherence (i.e., how coherently an individual views him or herself) predicted future, but not make-believe, event narrative generation in younger children. Therefore, the cognitive concept of the self might be required to engage in mental travel across the temporal, but not the hypothetical, dimension. Given that self-concept coherence improves significantly with age (Coughlin et al. Reference Coughlin, Robins and Ghetti2019), it makes sense that traversing the temporal dimension emerges later than traversing the hypothetical one. Similarly, contrary to what might be expected were all dimensions equal, Hanson et al. (Reference Hanson, Atance and Paluck2014) found that 3- to 5-year-olds' performance on theory of mind tasks (i.e., traversing social distance) was not related to their performance on episodic foresight tasks (i.e., traversing temporal distance). In sum, these are not the findings we would expect based on the idea that the capacity to mentally travel across different dimensions co-occurs in ontogeny.
Future research should systematically test children's sensitivity to the various dimensions in a single task (e.g., producing event narratives) while varying the dimension that must be traversed. For example, based on our account, children may show greater ease imagining how an event might unfold for another child than they do imagining how this event may unfold at a distant spatial location, or even for their future selves. This may be why in certain contexts, children's future-oriented decision-making is more accurate and adaptive for “other” than “self” (Bélanger et al. Reference Bélanger, Atance, Varghese, Nguyen and Vendetti2014; Prencipe & Zelazo Reference Prencipe and Zelazo2005; for a similar study with adults, see Renoult et al. Reference Renoult, Kopp, Davidson, Taler and Atance2016). Further exploring the cognitive correlates of each form of mental travel would also continue to shed light on why some forms may emerge earlier than others. The results of such efforts may not fundamentally contradict Gilead et al.'s claims, but may instead add richness and precision to an account of how humans develop the remarkable capacity for mental travel.
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We appreciate Gilead et al.'s highlighting of the various “epistemic barriers” or “dimensions” (in addition to “time”) that humans must mentally traverse. Inherent to their theory of mental travel is that the different dimensions/distances (i.e., temporal, spatial, social, and hypotheticality) are intertwined, mostly interchangeable (thus lumped together under the broader construct of “mental travel”), and co-occurring in ontogeny. However, this characterization overlooks important nuances between different forms of mental travel and the diverse representational capacities subserving them. This is especially apparent in recent cognitive developmental data suggesting that children's sensitivity to different dimensions emerges in a staggered manner, and that the capacity to traverse dimensions may rely on different underlying representational capacities.
Developmental research has not yet provided a comprehensive account of when different forms of “mental travel” emerge and, importantly, whether sensitivity to each dimension emerges simultaneously. Yet, new data suggest important differences as a function of the dimension children must traverse. A notable point is that traversing social distance appears to emerge early in development. For example, taking a socially distanced perspective (by reasoning about “other” vs. “self”) enhances 3- to 5-year-olds' ability to predict future preferences (Bélanger et al. Reference Bélanger, Atance, Varghese, Nguyen and Vendetti2014; Lee & Atance Reference Lee and Atance2016) and delay gratification (Prencipe & Zelazo Reference Prencipe and Zelazo2005). Social distancing also improves executive functioning in this same age group. White and Carlson (Reference White and Carlson2016) found that preschoolers who took the perspective of another character (e.g., Batman) during an executive functioning task showed increased performance compared to preschoolers whose perspective was focused on the self. This effect was, however, more pronounced for 5- than 3-year-olds suggesting that even though young preschoolers are sensitive to social distance manipulations, this sensitivity increases with age.
Interestingly, however, preliminary work also suggests that children's sensitivity to spatial distance emerges later than sensitivity to social distance. For example, although taking a socially distanced perspective improved preschoolers' ability to predict future preferences (Bélanger et al. Reference Bélanger, Atance, Varghese, Nguyen and Vendetti2014) and delay gratification (Prencipe & Zelazo Reference Prencipe and Zelazo2005), Rutt et al. (Reference Rutt, O'Brien and Atance2019) recently showed that a spatial distance manipulation had no such facilitative effect. Specifically, 3- to 6-year-olds who were asked to take a spatially distanced perspective by imagining themselves in a far-away place were no more accurate in predicting future preferences, nor delaying gratification, than children who adopted a spatially near perspective (i.e., their current location). Similarly, Bowman-Smith et al. (Reference Bowman-Smith, Shtulman and Friedman2019) found that a spatial distance manipulation did not have a significant effect on children's reasoning until 6½. These findings, thus, suggest important differences between mental travel across social and spatial distances.
Findings by Coughlin et al. (Reference Coughlin, Robins and Ghetti2019) provide further evidence of differences between forms of mental travel. They compared 5-year-olds', 11-year-olds', and adults' ability to produce “temporal” and “make-believe” (i.e., hypothetical mental travel) narratives about a particular event (e.g., eating something yummy). Five- to 11-year-olds required more prompts to successfully produce future event narratives, and also received lower episodicity (i.e., amount of episodic detail) scores on future narratives, as compared to make-believe event narratives. Older children also required fewer prompts than younger children to produce future event narratives, whereas the number of prompts required for make-believe events did not differ with age. These findings suggest that the ability to mentally traverse time emerges later than the ability to mentally traverse hypotheticality.
Therefore, although we agree that different forms of mental travel might be largely interchangeable in adults, they appear to develop in a staggered manner in childhood. Though more data are needed, traversing (or being sensitive to) social (Bélanger et al. Reference Bélanger, Atance, Varghese, Nguyen and Vendetti2014; Lee & Atance Reference Lee and Atance2016) and hypothetical distances (Coughlin et al. Reference Coughlin, Robins and Ghetti2019) appear to emerge earlier in development than traversing temporal (Coughlin et al. Reference Coughlin, Robins and Ghetti2019) and spatial distances (Bowman-Smith et al. Reference Bowman-Smith, Shtulman and Friedman2019; Rutt et al. Reference Rutt, O'Brien and Atance2019).
In light of this, it is unsurprising that the mental representations (or forms of “abstraction”) subserving the various dimensions of mental travel also appear to differ. For example, as described earlier, Coughlin et al. (Reference Coughlin, Robins and Ghetti2019) found that young children were better able to episodically pre-experience a hypothetical, than a future, event even though both dimensions require event simulation. Importantly, these authors found that self-concept coherence (i.e., how coherently an individual views him or herself) predicted future, but not make-believe, event narrative generation in younger children. Therefore, the cognitive concept of the self might be required to engage in mental travel across the temporal, but not the hypothetical, dimension. Given that self-concept coherence improves significantly with age (Coughlin et al. Reference Coughlin, Robins and Ghetti2019), it makes sense that traversing the temporal dimension emerges later than traversing the hypothetical one. Similarly, contrary to what might be expected were all dimensions equal, Hanson et al. (Reference Hanson, Atance and Paluck2014) found that 3- to 5-year-olds' performance on theory of mind tasks (i.e., traversing social distance) was not related to their performance on episodic foresight tasks (i.e., traversing temporal distance). In sum, these are not the findings we would expect based on the idea that the capacity to mentally travel across different dimensions co-occurs in ontogeny.
Future research should systematically test children's sensitivity to the various dimensions in a single task (e.g., producing event narratives) while varying the dimension that must be traversed. For example, based on our account, children may show greater ease imagining how an event might unfold for another child than they do imagining how this event may unfold at a distant spatial location, or even for their future selves. This may be why in certain contexts, children's future-oriented decision-making is more accurate and adaptive for “other” than “self” (Bélanger et al. Reference Bélanger, Atance, Varghese, Nguyen and Vendetti2014; Prencipe & Zelazo Reference Prencipe and Zelazo2005; for a similar study with adults, see Renoult et al. Reference Renoult, Kopp, Davidson, Taler and Atance2016). Further exploring the cognitive correlates of each form of mental travel would also continue to shed light on why some forms may emerge earlier than others. The results of such efforts may not fundamentally contradict Gilead et al.'s claims, but may instead add richness and precision to an account of how humans develop the remarkable capacity for mental travel.