Effects of Context on Target Localization

The purpose of this thesis was to investigate how the presence of non-target objects can influence the planning of a movement towards a remembered target location. One specific aim was to examine how the temporal effects of the task could affect movement planning. The final aim of this thesis was to examine whether or not the mere presence of extrinsic cues can suppress the encoding of intrinsic cues. It was found that when non-target objects are presented simultaneously with the target, interference occurs; however, if the non-target objects are presented at least 250 ms in advance of the targets performance improved. The results also revealed that uncertainty regarding trial type altered participants’ response strategy. It appears as though when participants can anticipate when the response is required, they plan the movement as the trial progresses, however, it appears as though when there is uncertainty participants either suppress their movement plan or hold the representation of target location and only plan the movement when uncertainty has been resolved. Furthermore, the results of Experiments 3 and 4 indicated that participants automatically encode target location within an extrinsic reference frame when non-target objects are available. The principal conclusion was that movement planning is clearly affected by the presence of non-target objects