| Human being has a long history,but the Earth has an even longer past.Human beings are the most intelligent species the Earth has born till now,whose history is a process of adapting to the Earth and empowering themselves,so it was not only our instinct but also our skill to learn to survive on the Earth.The Earth is three-dimensional and even multi-dimensional,and it is the most basic requirement to know how to walk,dodge,search and arrive on the Earth.So it is not only of great significance for the survival of human being to know how we represent and memorize the spatial location of various objects on the Earth,but also of theoretical value for us to know the happening and development of human being’s spatial intelligence.The appropriate representation and memorization of objects’ spatial location is the foundation of all spatial behaviors.When one doesn’t know the specific position of a given object,it is impossible to get away from,search for,or arrive at it,not to mention implement some spatial tasks relevant to it.The representation and memorization of the given object depends on the frame of the reference,from which the spatial substance and certainty is assigned to the object’s location.At present,the researchers have done lots of studies on the spatial frame of reference,holding that self-centered frame of reference and object-centered frame of reference are two of the fundamental ones for human being to represent the location of objects.They also have studied the happening,dominating as well as the transiting mechanisms of special frame of reference but made different conclusions.Often,they found facts of object-centered representation in self-centered experimental paradigm and vice versa,and the transition between them was also analyzed from an opposite perspective.The dissertation,on the basis of analyzing and generalizing the flaws of the present experiments’ paradigm and research technology,beginning with the emphasis of the mathematical substance and factors,proposed a theoretical covariant framework of reference point and reference direction when spatial navigators represent object’s position,and made thorough analysis of how to value and choose the reference point and direction from the perspective that navigators are the subjects of spatial cognition.The dissertation has 5 studies and 10 experiments.(1)The first and the second study has 4 experiments,which manipulated the reference objects and reference directions in the virtual spatial settings to explore the conditions and characteristics when navigators chose "self " or objects in the setting as reference point and the learning direction of self as the reference direction.(2)The third study has only 1 experiment,which analyzed the cognitive processing of establishment and employment of internal frame of reference when navigators chose objects in the setting as reference point and spatial vectors as the reference direction.(3)The fourth study included 3 experiments and manipulated the appearance of reference objects to analyze the representation and priming mechanisms for internal frame of reference to represent objects’ locations,and explored the transitional mechanism to self-centered code when priming failure of internal representation happened.(4)The fifth study included 2 experiments,which conducted two-task paradigms to explore the requirements of self-centered representation and internal reference representation for cognitive workload,to answer the question of why navigator’s choice of reference point and reference direction would be constrained by cognitive workload,to provide experimental support to the analysis of choosing reference point and reference direction under the prerequisite of limited human cognitive resources,and to find theoretical basis for the analysis of transitional mechanism of spatial frame of reference.From the above five studies,the following conclusions can be made:(1)Without external reference objects in the setting,navigators would prime self-centered frame of reference with self as the reference point and learning direction as reference direction.Once navigator moved their spatial position,the reference point and direction needed to be upgraded and every object’s position in the setting needed to be recoded according to the new frame of reference.The more times navigators’position changed,the more times frame of reference needed to be upgraded,and the more deviations would be made.(2)The priming of allocentric reference frame was influenced by the conscious threshold of reference objects.It was found in the second experiment that,even with the existence of reference objects,when their dominance was restrained,the objects’ spatial representation would perform characteristics of egocentric coding;in the third and fourth experiments,under the same navigating setting,but when psychological expectation from navigators was rendered,an allocentric instead of egocentric frame of reference would be established.This explains the fact that as objects external to "ego"are used as reference object,navigators need to have certain level of acknowledgement of the "object".Only under this circumstance would external things be used as reference objects,and or else,what that is primed would be egocentric reference frame.(3)The existence of object-centered-ego-orientated frame of reference.From existing literature,naught was found about it.In experiment 3 and 4,the objects’location which were used as reference objects were manipulated and the directional vectors information that might provide direction for the position and shape of the reference objects were inhibited.The result found that central angular error that were aimed to reveal directional information showed characteristics of egocentric coding while distance error that were aimed to reveal distance information was stable,which performed dissociation from the direction to the distance of objects positional representation.It was because reference object couldn’t provide internal directional vectors,navigators could only make their own learning orientation as the reference direction and after realizing the road-sign function of reference objects,they established their own object-centered-ego-orientated frame of reference.(4)When the reference objects could provide directional vectors,navigators would establish internal frame of reference with the reference object as the origin and reference’s directional vectors as the reference direction.The reference point and direction of this frame is stable,which would not change with the spatial movement of the navigators.They can recognize their new position after every movement,which means the object-object relationship in internal reference coding is stable,and will not collect errors as navigators change their positions.(5)The internal frame of reference can code the position of objects in a visual snapshot manner.The position of the objects,references,and the directional vectors of the references can be abstracted into a stable triangular flat with the navigator’s visual snapshot,and be stored into the memory.In the following spatial tasks,if the navigators can prime and match the memorial image,then the object’s position of the internal reference representation can be primed.Or else,then navigators can make judgment according to sensory motor information and show the characteristics of egocentric coding.According to the theoretical framework hypothesis of navigators’ covariant choice of reference point and reference direction,ego-centric frame of reference can be renewed with the movement of navigators,and objects’ position in the setting can be recoded,while for internal frame of reference only navigators’ own position need to be upgraded,so ego-centric coding would employ more cognitive resources,which was supported by The results of experiment 9 and 10 that used double-task paradigms.However,some researchers argued that the ego-centric upgrading is conducted automatically and unconsciously without using cognitive resources,which might be because of the effect of sensory motor system.All the ten experiments in the present study have found common result:when the navigating routes are small in number,for example,if there is only 1 route,all the experiments,whether they are supportive of ego-centric or allocentric reference frame,have found that the memorization of object’s position was the most accurate.Especially in experiment 3 and 4,when only 1 route was navigated,the ego-centric coding accuracy reached the highest level.This showed that,for both ego-centric and allocentric coding,there might exist in their early period unconscious sensory motor system,which possesses the characteristics of ego-centric coding,though it did not last for long.As navigator continued,this system should change through spatial upgrading into ego-centric and allocentric coding in long memory. |
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