In the first line of studies, the project looked at individual differences, exploring variation in spatial memory across gender and age groups. A first exploratory study was designed as a stepping stone into examining the development of spatial and temporal memory. Participants were presented with five objects in a contextual cluster (e.g. objects one finds in a museum, in a garden, etc.). The objects were presented one-by-one at a given location on the screen, at a given order. The contextual information was manipulated in 3 levels: no context, 3 landmarks on the screen, or a full image in which objects were placed at ‘possible’ locations (ie,. objects would be on a shelf, the floor, etc). After object presentation, participants indicated first which objects they saw (testing object memory), then in which order they saw them (temporal memory), and finally where in the scene they saw the objects (testing object-location binding). We found a significant effect of age, but no effect of gender. One reason for this might be a floor effect, as most age groups performed at (near) ceiling level when remembering the 5 objects and their order of presentation. Follow-up studies are planned with an increased level of difficulty, to increase the variation in results and allow a more fine-grained distinction between participant groups. This line of work confirmed the initial proof of concept and paved the way for further confirmatory studies, which are currently being planned.
A second line of research looked at the effect of object knowledge on spatial memory in a screen-based paradigm. Combining previous research on the effects of object knowledge on object location memory with research on boundary extension. Previous studies have shown that ownership, or the mere suggestion of ownership, biases memory for both objects and their location. Specifically, when an object is owned, it is remembered to be closer by compared to objects that are not owned. Conceptually this can be seen as a ‘zooming in’ on owned objects compared to not-owned objects. This was compared to research on boundary extension, in which people extend on the boundaries of scenes in their memory, such that they ‘remember’ a larger scene upon memory than was originally present. Conceptually, this can be seen as a ‘zooming out’. In this line of research we combined these two, and presented participants with images of objects in scenes, in which ownership (owned or not) to objects was assigned. In the first study, we found a significant reduction of boundary extension in scenes with ‘owned’ objects. While results showed a boundary extension of approximately 5% in the ‘not-owned’ condition, this was only 2% in the ‘owned’ condition. To follow-up on this effect we planned a study with two tweaks. First, we hypothesised that the effect might be that participants assumed ‘owned’ trials were more important, so we manipulated the ‘importance’ of trials. By indicating trials might come back for another question later in the experiment, we crossed the manipulation of ownership with importance. A second level was planned to look at cultural variation, comparing Western participants with East-Asian participants, which have been shown to process and remember scenes more holistically. However, when replicating the initial findings with the Western group (importantly, the stimuli where updated as well), results did not show significant differences. The planned replication with East Asian students was therefore postponed, in order to explore whether the failed replication falsified the earlier findings or whether the absense of effects were caused by the changed experimental design. A follow-up study is in preparation.
A final novel, behavioural study design tested memory for object location in real 3D space, by contrasting object locations within and out of reach on the sagittal and the lateral axis. A TV-screen was put flat on a table, in order to manipulate object locations specific to individual participants reach – before the study participicants performed a non-related task in which they would place objects as far as they could reach on the screen. During this calibration were blindfolded as to not give them visual feedback of how far they could reach. Each individual participants’ reach was used as a baseline, to present objects within, or out of reach, and test whether reachability judgments as well as object location memory are biased towards the dominant hand. The results are currently being analised and expected to lead to a stand-alone publication.
Next to studies targeting individual differences designed and executed within the project, the researcher also pursued collaborations in additional related projects investigating individual differences in spatial communication, spatial language in bilinguals, spatial recognition in second language learning, and spatial language development during infancy. These led to 4 separate publications.
The second overarching line of studies looked at the neural correlates of object location memory. A mock study was conducted to confirm that the effects previously found in behavioural tasks with participants sitting at a table would replicate in an MRI-setup, in which participants would be lying down. An additional mock-scanner study was run to test the reliability of the designed apparatus, which reached an error-rate of 1 in 700 trials. After these two mock-studies confirmed proof of concept, we ran two fMRI studies, investigating the neural correlates of spatial memory, including topographic mapping of the SPOC area and neural correlates involved in perceiving objects at varying three-dimensional distances, as well as those associated with object location memory across these distances. Participants were lying in the MRI-scanner, with their heads propped up to approximately 40. This allowed them direct vision of objects presented on the apparatus. Data collection of two studies (both N = 30) has been completed and data analysis for these studies has commenced. While the anticipated behavioural effect of object knowledge on OLM did not emerge as expected, the collected neuroimaging data is currently being analysed and is still expected to provide valuable insights on the neural correlates for spatial memory and a building block for future research.
