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Stable Egocentric Representation Acquired from Sequential Proprioceptive Learning
XIAO Chengli
2013, 45 (7):
752-761.
doi: 10.3724/SP.J.1041.2013.00752
It is generally believed that the egocentric representation is transient and primarily supported by perception. However, recent theories suggest that the egocentric representation can be an enduring component and preserved in memory. Wang (2012) proposed that the enduring egocentric representation, also referred as the egocentric snapshot, was stable and would not be disrupted by disorientation. She further suggested that the egocentric snapshot was not restricted to retinal images and could be acquired from other modalities. Her statement is consistent with the functional equivalence hypothesis (Loomis et al., 2007). These hypotheses were examined in the present study. Thirty two university students (16 men and 16 women) participated in this experiment in return for monetary compensation. Participants stood at a learning position amidst a geometrically irregular 9-object array. Half of them viewed the layout with objects being simultaneously presented, and the other half were blindfolded and led to sequentially walk to each object’s location from the learning position (proprioceptive learning). After learning the layout, all the participants were blindfolded and tested in the baseline, updating, and disorientation conditions in sequence. In the baseline condition, participants maintained their heading to scissors. In the updating condition, participants rotated 240° by themselves. Within each group, right before rotation, half the participants were explicitly instructed to use allocentric spatial relations during locomotion. The other half were not given such instruction. In the disorientation condition, participants rotated in situ until got disoriented. In each locomotion condition, it included four blocks of trials, each block involving pointing to all nine objects once in a random order. The major dependent measure was the configuration error, defined as the standard deviation of the means per target object of the signed pointing errors, which indicated the internal consistency of the pointing response among different targets. An increased configuration error after disorientation provides evidence of a disorientation effect, indicating the use of the transient egocentric representation, whereas an equivalent configuration error between these two conditions indicates the use of stable spatial relations. Finally, all participants were taken to another room to perform judgments of relative direction (JRDs) among the remembered object locations. The JRDs test included 48 trials, six trials at each of eight imagined headings (0° to 315° at 45° intervals). The dependent measures were the absolute angular error and the latency of the pointing response. Configuration errors on egocentric pointing were subjected to mixed-model analyses of variance (ANOVAs), with locomotion condition (baseline, updating, and disorientation) as the within subject variable, learning modality (vision, proprioception) and allocentric instruction (yes, no) as the between subjects variables. The results revealed no main effects or interactions of allocentric instruction. The configuration errors increased after the rotation of the participants who visually learned the layout, but were equivalent before and after the rotation of the participants who proprioceptively learned the layout. The configuration errors were indistinguishable for visual and proprioceptive learning in the baseline and the updating conditions, but significantly larger for visual learning than for proprioceptive learning in the disorientation condition. Performance data on JRDs were subjected to mixed-model analyses of variance (ANOVAs), with imagined heading (0° to 315° at 45° intervals) as the within subject variance, learning modality (vision, proprioception) and allocentric instruction (yes, no) as the between subjects variables. The results revealed no main effects or interactions of allocentric instruction. The participants’ performance on JRDs was indistinguishable for visual learning and proprioceptive learning, which indicated that participants constructed an allocentric spatial representation of equivalent fidelity through visual and proprioceptive learning. In conclusion, the results in the present study provided evidence that participants constructed a stable egocentric representation when they proprioceptively learned the irregular object array. These results are parallel to Xiao & Chen’s (2012) finding, and support Wang’s (2012) generalization of the egocentric snapshot and functional equivalence hypothesis.
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