Use of Geometric Cues in Spatial Reorientation

                     Experiment Report

 Name: Jin Yan       Major:   Psychology      No: 2015214121   Report time:  2017.4.24    

Use of geometric cues in spatial reorientation

1. Abstract

Determining one’s position within an environment is an important first step in navigation. The use of two kinds of geometric cue—the global geometric cue and the local geometric cue, was tested in this experiment. The results of this experiment showed that only in a global-cue-only condition, the number of people in fit category was higher than chance level, indicating that human adults are able to reorient to multiple objects within the local environment by using the global geometric cues. This finding supports the geometric template model, whereas contradicts the BVC model.

2 Introduction

Determining one’s position within an environment is an important first step in navigation. Research found that there are two types of visual-based environmental cues that an organism can use to reorient: featural and geometric cues. Featural cues include distinctive information such as the pattern, texture, and/or color of objects or surfaces within an environment (e.g. the landmark). Geometric cues refer to the inherent characteristics within enclosed environments, such as the overall shape of the space as defined by both the lengths of individual walls and the angular information provided by corners. Cheng (1986) found that in a reorientation task, rats used the shape of the room for reorientation but did not use the distinctive objects or features to avoid the rotational corner. According to this finding, he proposed that there’s a purely geometric module in the rat’s spatial representation, which is solely sensitive to geometric information and responsible for processing it. With the going deep of the research, researchers distinguished two types of geometric cues—global geometric cues (shape as defined by relative lengths of walls) and local geometric cues (the specific characteristics such as angle, length, distance, orientation), and have got some new insights of the reorientation mechanism. Contrary to Cheng’s assertion that only global geometric cues was used in reorientation, for instance, Tommasi and Polli (2004) found chicks can reliably use the global geometric information as well as the local geometric information to orient. The boundary vector cell (BVC) model (1996) interpreted the use of spatial cues on the level of neurobiology. This model proposed that the local spatial information can be integrated in hippocampus and consequently forms into a global representation of space. So this model suggests that both global and local geometric cues can be used, and the global representation can be formed by the integration of local representation without the enclosed boundary.

2.1 Experiment objective

This experiment is aimed to test which kind of geometric cues is used in the reorientation task in a carefully controlled virtual-reality environment so as to judge whether geometric module hypothesis or BVC model is more appropriate to interpret the use of spatial cues in navigation.

2.2 Experiment content

  We used a variant of a reorientation paradigm developed by Reichert and Kelly (2010). In training phase, both global geometric cues and local geometric cues were provided and participants needed to remember the orientations of five objects scattered at a virtual-reality environment. In test phase, after being disoriented, participants were requested to orient these objects in global-cues-only conditions and local-cues-only conditions.

1. Experiment meaning

This experiment used virtual-reality instrument, increasing the relationship with nature. So it improved the vraisemblance of the On the basis of test geometric module hypothesis and BVC model, this experiment can help us get a deeper understanding of spatial reorientation.

3 Method

3.1 Subject   

Seven participants (1 male, 6 females) from Central China Normal University (CCNU). All participants had normal or correct-to-normal vision.

3.2 Equipment or material

Equipment: some necessary equipment were used to construct a virtual reality environment

Materials: 5 objects for reorientation task, respectively, a scissor, a ball, a bottle, a brush, and a candle and four angles (two angles: 30◦; two angles: 75◦) were constructed in VR-environment.

3.3 design

Two types of angles (four angles in total) with differing degrees were used (i.e. 30◦ and 75◦). Each angle was located in one vertex of an imaginary rectangle, and the angles with the same type were diagonally opposite to each other. Therefore, two types of geometric cues were used in this experiment. The local geometric cue referred to the four angles, and the global geometric cue referred to the imagery rectangle composed by four angles. Depending on the kinds of cues, there were three different conditions: the local cues condition, the global cues condition, the global & local cues condition. In the global & local cues condition, the configuration was the same as that in learning phase. In the global cues condition, all angles were right angles, and they still were located in the vertexes of an imaginary rectangle. In the local cues condition, two types of angles were located in the vertexes of an imaginary square. The schematic representation of the configuration of each kind of condition is shown in Figure 1.

[pic 1]

Figure 1 the schematic representation of the configuration of each kind of condition

  Two phases were included in this experiment. In the training phase, two kinds of geometric cues were provided in VR environment. Participants have 4 chances to learn the orientation of objects based on the external cues (local and global cues). In the test phase, first participants were tested in G & L condition. This condition is regarded as a baseline condition to test whether participants’ memory about the target location was accurate. Then, under the state of misorientation, the orientation accuracy was respectively test in the condition with global cues or local cues. Each block has 4 trials. So the training phase included 4 trials; the test phase included 12 trials; and in total, 16 trials were included in this experiment. The order of each kind of blocks in testing phase and the testing orders of objects in each trial were random.