Elsevier

Human Movement Science

Volume 85, October 2022, 102979
Human Movement Science

Locomotion training contributes to 6-month-old infants' mental rotation ability

https://doi.org/10.1016/j.humov.2022.102979Get rights and content

Abstract

This study investigated whether a locomotion training contributes to mental rotation performance in infants. Thirty 6-month-old pre-locomotor infants were randomly assigned to either a locomotion training or a control group which received no training. The general status of motor and cognitive development measured with the Bayley Scales did not differ between the 2 groups. Mental rotation was compared before and after the trainings using a mental rotation task in which infants were habituated to a rotating object and then tested with the same habituation object presented in a previously unseen angle and the corresponding mirror object. Results revealed that only infants in the locomotion training group showed a significant change in their looking durations at the test objects (habituation vs. mirror) in the mental rotation task. This suggests that self-produced locomotion experience can affect infants' mental rotation.

Introduction

Mental rotation refers to the ability to rotate mental representations of two- and three-dimensional objects (Linn and Petersen, 1985). This ability is already essential for infants when they learn to interact effectively with objects of their daily use in an ever-changing environment. Mental rotation enables them to process these many changes by, for example, recognizing objects from different points of view or predicting their specific orientation when they are moved. However, it is not yet fully understood which factors drive this key ability in infants. In line with theories stating that infants' self-produced action is connected to their perceptual and cognitive progress, it has been discussed whether the emergence of infants' self-produced locomotion such as crawling is a crucial factor for their mental rotation ability. Accordingly, several studies compared same-aged crawling and non-crawling infants' mental rotation ability and found that crawling infants' mental rotation performance was better than that of non-crawlers (Gerhard and Schwarzer, 2018; Schwarzer et al., 2013a; Schwarzer et al., 2013b). However, these studies were quasi-experimental and could not clarify whether locomotion is indeed a significant factor driving infants' mental rotation ability. They could not definitely determine whether infants' locomotion experience in fact improved their mental rotation ability, or whether the improvement was driven by some additional uncontrolled variable. For instance, it could have been that the crawling infants were cognitively more advanced than the same-aged non-crawlers, and would have therefore shown a performance advantage in mental rotation. A study design that can address this question would manipulate locomotion experience, and assess the effects of such experience on infants' mental rotation abilities. It was the aim of the present study to use such a design in order to investigate whether the emergence of infants' self-produced locomotion experience contributes to an improvement in their mental rotation performance. We conducted a training study with pre-locomotor 6-month-old infants who were randomly assigned to receive either locomotion training or no training. We compared the infants' mental rotation performance before and after this intervention.

Early work on mental rotation demonstrated that infants at 4 months of age are able to track and anticipate the final orientation of an object after it passes and rotates through an occluder (Hespos and Rochat, 1997; Rochat and Hespos, 1996). Further studies have shown that 3- to 5-month-olds can also distinguish a familiar object seen at a novel rotation angle from its mirror image. Moore and Johnson (2008), for example, habituated 5-month-olds to an object that rotated back and forth in a 240° arc. The infants were then tested with the same object after being rotated through the previously unseen 120° arc and the corresponding mirror object after a similar rotation. Boys but not girls looked longer at the mirror object, suggesting that they could rotate the mental representation of the object. Christodoulou et al. (2016), also studied 5-month-olds and used a similar method. In this study, however, they did not find a gender effect; across gender they revealed a preference for the familiar object. Such a familiarity preference was also found with even younger infants, 3-month-olds, this time, however, only in boys. Girls did not show a preference at all (Moore and Johnson, 2011). Further evidence of gender effects was provided by studies carried out by Quinn and Liben, 2008, Quinn and Liben, 2014 using a different method. They familiarized 3- to 4-month-old infants as well as 6- to 10-month-olds with a series of two-dimensional images of the numeral “1” and then preference-tested them with a novel orientation of the numeral “1” paired with its mirror image. They found that boys displayed a novelty preference for the mirror image, but girls did not. Evidence for sex differences was also provided by Lauer et al. (2015). The authors found an interesting relation between mental rotation tested with a detection task and object preference depending on the infant's sex. Greater visual interest in male-typed objects was linked to greater mental rotation performance in boys, but not in girls. However, another series of experiments (Kaaz and Heil, 2019) provided mixed evidence with some results showing effects of sex on mental rotation while others revealed no such sex effects. Johnson and Moore (2020) concluded in their review that there is a relatively even distribution of findings either showing or not showing sex differences, calling for further research on the underlying causes of this difference.

In addition to this line of research investigating the role of sex in infants' mental rotation ability, further research links infants' mental rotation development to their motor skills development. Developmental psychology has a long history of connecting achievements in infants' motor skills with improvements in perceptual and cognitive abilities. Piaget (1952), for example, assumed that infants' understanding of objects is based on information acquired through sensorimotor experiences or actions, arguing that action is the origin of cognition. Other researchers (e.g., Adolph et al., 1993; Bushnell and Boudreau, 1993; Gibson, 1988) have proposed that infants' action systems tune their perceptual systems, which allows them to gain new information about objects. Embodied cognition research also argues that infants rely on information produced by the coupling of action and perception when learning to perceive and represent objects (Bahrick et al., 2004; Gibson and Pick, 2000; Smith and Gasser, 2005). These theoretical approaches motivated our research question of whether infants' self-produced locomotion activities are related to their developing mental rotation ability.

The onset of self-produced locomotion in the form of crawling is one of the most important transitions within the first year of life, and involves a remarkably broad set of changes in psychological functioning such as those in the visual-spatial processing of objects (Anderson et al., 2013; Campos et al., 2000). Regarding spatial search tasks, in which infants are asked to manually search for objects hidden in one or two locations, Kermoian and Campos (1988) compared the search performance of 3 different groups of 8.5 month-old infants with differing experience with locomotion: pre-locomotor infants, pre-locomotor infants with experience moving in a wheeled-walker, and infants with hands-and-knees-crawling experience. Results revealed that infants with hands-and-knees crawling experience or experience moving in a wheeled-walker outperformed the pre-locomotor infants in the search task. In another experiment, the authors also tested same-aged belly crawling infants with the same search task, and showed that those infants performed similarly to the pre-locomotor infants. The authors argued that belly crawling is so effortful and inefficient, that the belly crawlers were unable to deploy attention to the environment in the same way that hands-and-knees-crawlers and infants in walkers could. Campos et al. (1980) studied the relation between infant crawling experience and their ability to recognize different shapes of objects independently of orientation, size, and color. The study found that the performance of infants who were crawling was significantly better than that of non-crawling infants. Another study by Campos et al. (2009) found the same link in infants with spina bifida. This study showed that these infants' onset of crawling was related to an enhanced ability in a two-position object permanence manual search task.

Similar relations to self-produced locomotion were also demonstrated when infants were examined using mental rotation tasks. By using a variation of the mental rotation task of Moore and Johnson (2008), Schwarzer et al. (2013a) as well as Gerhard and Schwarzer (2018), found that only 9-month-old infants who were able to crawl looked longer at the mirror objects than the habituation objects, indicating that they were able to mentally rotate the habituation object. By contrast, same-aged infants without crawling experience were not able to distinguish between the mirror and habituation object. However, when infants' mental rotation performance was tested in relation to their free manual object exploration behavior in addition to their crawling ability as in the study by Schwarzer et al. (2013b), the non-crawlers‘ looking times were influenced by their manual exploration scores. The non-crawlers who did not spontaneously explore toy blocks in the manual exploration task tended to show a familiarity preference, whereas those who explored the toy blocks in an advanced manner preferred to look at the mirror object. Frick and Möhring (2013) who tested 8- to 10-month-old infants’ looking time at possible and impossible orientations of p and q stimuli also found a significant relationship between infants' crawling ability and their looking behavior toward the impossible event.

Thus, various converging research methods have shown that infants who can locomote via crawling or via a wheeled-walker performed better on spatial search and mental rotation tasks than infants who cannot. However, it has not yet been shown that locomotion significantly contributes to infants' increase in visual-spatial abilities. So far, such an influence of locomotion has only been shown for infants' visual proprioception (Uchiyama et al., 2008) and infants' wariness of heights (Dahl et al., 2013). In these studies, the authors used a random assignment of pre-locomotor infants to either a locomotion training using a powered mobility device (PMD) or a control condition, and tested infants' responses to peripheral optic flow and their cardiac responses indicating wariness of heights. In a three weeks lasting PMD training, the infants were taught to pull a joystick, which caused the PMD to move forward. The results provided evidence that the locomotion training significantly affected infants' postural compensation and their cardiac indications of wariness of heights. As the experimental design of these studies involved random assignment of pre-locomotor infants to either the PMD or a control condition not receiving any locomotion experience at all, locomotion experience can be understood as a significantly driving factor of the changes in the infants' responses to peripheral optic flow and wariness of heights. As mentioned previously, there have not yet been any studies which tested directly the contributing role of infants' locomotion experience in their visual-spatial abilities such as mental rotation.

The present study was aimed at filling this gap in research by investigating whether infants' self-produced locomotion is driving their mental rotation ability. A study design which allows for answering this question is a training experiment in which locomotion experience is manipulated in pre-locomotor infants, combined with the measurement of the effect of such experience on infants' mental rotation performance. Therefore, in the present study we conducted a training study with pre-locomotor 6-month-old infants who we randomly assigned to a locomotion training group and a control group in which infants did not receive any locomotion experience. In the training group, we taught the infants over 3 weeks to process a visual surrounding while locomoting in a wheeled-walker. We chose to use walker training because Kermoian and Campos (1988), as mentioned earlier, were able to show that pre-locomotor infants who had experience with moving in a walker performed similarly to crawling infants, and significantly outperformed same-aged pre-locomotor infants in a visual-spatial task.

Before and after the trainings, we tested the 6-month-old infants' mental rotation performance with a task used by Schwarzer et al. (2013b). At both testing times, infants were habituated to a rotating object and then tested with the same habituation object presented in a previously unseen angle and the corresponding mirror object. If infants were able to recognize the habituation object in the previously unseen rotation angle but did not prefer to look toward the novel, mirror object at test, we expected them to look longer toward the habituation object. However, if they were able to recognize the habituation object in the previously unseen rotation angle and then preferred to look at the novel, mirror object at test, we expected them to look longer toward the mirror object. When they were not able the recognize any of the two test objects we expected them to show no difference in the corresponding looking times.

As the infants in the present study were only 6 months of age and not able to locomote and according to results using the same method with 9-month-old non-crawling infants, at pre-training testing, we expected infants in both groups not to be able to differentiate between the familiar and mirror object and to look nearly equally long at the two objects. At post-training, we hypothesized that infants who participated in the locomotion training would be able to differentiate between the familiar and mirror object and particularly look longer to the mirror object while we expect infants in the control group not to be able to do so.

Section snippets

Ethics statement

The present study was conducted in accordance with the German Psychological Society (DGPs) Research Ethics Guidelines. The Local Office of Research Ethics at the University of Giessen, Germany approved the experimental procedure and the informed consent protocol. For each infant, written consent for participating in the study was obtained from the parents.

Participants

According to the effect sizes of a previous study on the relation between crawling and infants‘ visual-spatial processing (Kubicek et al.,

Outcomes of the locomotion training

In order to determine which specific experience the infants were exposed to in the locomotion training, we measured the overall duration of the training, averaged duration per training session, number of rounds, and the number of stops in front of the locomotion targets. We revealed that the overall duration of the training was M = 131.31 min, SD = 15.93 min, the average duration per training session was M = 16.55 min, SD = 1.98, the number of rounds across the training sessions was M = 15.11,

Discussion

The motivation of the present study was to investigate whether it is possible to change the mental rotation performance of pre-locomotor infants by providing them with self-produced locomotion experience in a rich visual surrounding. In particular, we wanted to know whether a locomotion training with a baby-walker can change pre-locomotor infants' looking behavior toward habituated objects versus their mirror objects in a mental rotation task compared to infants who did not receive any

Funding

This study was supported through a grant from the Collaborative Research Center SFB/TRR 135/1/2 2014, 2018 at the German Research Foundation.

This work was also supported by the Hessisches Ministerium für Wissenschaft und Kunst (HMWK; project ‘The Adaptive Mind’).

CRediT authorship contribution statement

Gudrun Schwarzer: Conceptualization, Methodology, Formal analysis, Writing – original draft, Supervision. Gloria Gehb: Software, Project administration, Investigation, Writing – review & editing. Amanda Kelch: Software, Investigation. Theresa Gerhard-Samunda: Conceptualization, Methodology. Bianca Jovanovic: Conceptualization, Methodology, Writing – review & editing.

Declaration of Competing Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Acknowledgements

We wish to give a special thank you to the student research assistents for their help with recruiting subjects, data collection and coding, as well as to all the parents who kindly agreed to have their infants participate in the study.

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