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Final Report Summary - SPATIALDEVELOPMENT (The development of spatial representations: a prospective and retrospective approach)

Project Objectives

Human senses like touch, vision and proprioception (the position of your body and limbs) are known to be represented in the brain in a common (spatial) reference frame. The main aim of this project was to investigate the developmental time course of this spatial reference frame. We took two main approaches: Studies 1 and 2 investigated the influence of spatial and non-spatial object characteristics on object differentiation performance. Studies 3 and 4 investigated visuo-proprioceptive adaptation as a marker of the development of the spatial reference frame. The findings of the studies in this project converge to a fully developed and automatically used spatial reference frame around the age of 8 years old.

Description of Work Performed

Study 1: Exploratory Procedures and Object Recognition

In order to perceive objects, we need know and combine their characteristics: for example their shape, size, texture and weight. Some of these characteristics are spatial (e.g. shape), while others are not (e.g. texture). In this series of experiments we investigated whether specific hand movements (so called exploratory procedures) are needed in order to differentiate between objects that differed in only one characteristic (size, shape, texture or weight). To test whether the spatial reference is not only developed, but also used automatically we applied a critical manipulation: we instructed which dimension they had to pay attention to in half of the trials, and in the other half we instructed them to do how they felt it was best (spontaneous condition). If participants are accurate in both conditions, they use the spatial reference frame automatically. If participants perform well in the instructed condition, the spatial reference frame has been developed, but if they do not perform well on the spatial characteristics in the spontaneous condition, the spatial reference frame is not used automatically.
In Study 1A, 40 participants in 2 age groups were tested in a singleton search experiment, we found that 4 year olds are slower and less accurate at finding a target differing from distractors by both spatial and non-spatial characteristics. This was true for both an instructed and a spontaneous condition in the experiment, with instructed accuracy being higher than spontaneous. However, interestingly, both age groups did show similar hand actions as compared to adults.
In Study 1B, 20 participants were tested in an object sorting task and we showed that adults have a preference for texture when asked to sort objects in two groups based on one of the 4 characteristics. This preference was only present in the spontaneous condition and not in the instructed condition.
Study 1C, around 90 participants in 6 age groups were tested in an ambiguous search task in which they needed to choose one of two possible targets. The results revealed that young children prefer a non-spatial characteristic as the defining difference between target and distractor. Around the age of 8 years old, participants show similar behaviour to adults. However, all participants show perfect performance on both spatial and non-spatial characteristics when they were instructed to do so.

Study 2: Contour Following and Object Recognition

In Study 2 we tested around 90 participants in 6 age groups in a visual and haptic 2D shape recognition task. By doing so, we fixed the way participants had to explore the stimulus materials to the contour following exploratory procedure (a spatial procedure). The data showed that children below the age of 10 were unable to recognize any objects (not visually and not haptically), indicating that they cannot use the information revealed by this spatial exploratory procedure.

Study 1 and 2 revealed that - independent of the exploratory procedures that were used - children up to 8 years old spontaneously use mainly non-spatial object characteristics to differentiate between objects. Although, when instructed they can perform the task also on a spatial level. These results point towards the spatial reference frame to be fully developed and automatically used around the age of 8.


Study 3 and 4: Visuo-proprioceptive adaptation

In Study 3 we tested around 700 participants aged 8-65 years old on a visuo-proprioceptive adaptation task in which they needed to align their unseen hand with objects in 3D virtual reality. We gave distorted feedback (shifted 10 cm horizontally), so that the participants had to adapt to a new spatial map in order to perform the task well. We showed that children and adults adapted similarly in this task, but that we can improve their performance by giving rewards.

In Study 4 we tested children from 4 till 10 years old and adults in a 2D virtual reality environment. Again, we asked participants to move their unseen hand to targets. This time we rotated the feedback of their hand position by 30 degrees. Again they needed to adapt to the distortion to be able to perform the task well. The youngest children were adapting slower and to a lesser degree as compared to older children and adults. Testing is still ongoing.

Studies 3 and 4 reveal that children up to 8 years old adapt less to distortions in their perceived spatial hand position, as compared to older children and adults. This indicates that they cannot align their visual and proprioceptive map, a prerequisite for a fully developed spatial reference frame.

Main Results

In these 4 different experimental paradigms we have shown that children aged 8 years and older behave similarly to adults. We can therefore conclude from these studies that the spatial reference frame is fully developed and automatically used around that age.

Impact

Now that we know that the spatial reference frame is developed around the age of 8 years old, we contributed new fundamental knowledge on the working of the human brain. Moreover, we opened new fundamental questions for researchers to work on, for example the question whether the brain would be plastic enough to allow training of spatial tasks to induce spontaneous use of the spatial reference frame earlier in development. On a more practical note, designers of educational movement games and other robotic type applications for children can use this valuable information when designing new applications.

Related information

Reported by

UNIVERSITAET HAMBURG
Germany
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