Object Identification in Spatially Filtered Scene Background
Date Issued
2010
Date
2010
Author(s)
Chu, Ching-Fan
Abstract
Identification of objects in scene contexts is critical for behavioral actions. Yet, how scenes influence object identification remains uncharacterized. It has been suggested that the low-spatial frequency of scene context is beneficial for object identification through activating possible objects in the context frame subserved by parahippocampus (Bar, 2004). In the present study, we verified this model by investigating the influence of spatially filtered scenes on object identification. In three experiments, objects were the ones that frequently occurred in the scenes and hence, were semantically and thematically congruent. In Experiment 1A, objects and scenes were spatially filtered by the same cutoff frequency (low- or high-passed at 1, 3, or 5 cpd). Objects were presented for 36 ms either alone without scene background or in scene contexts. Results showed that scene decreased the performance of object identification. The same results were obtained in Experiment 1B where stimuli were presented until response. In Experiment 2, we investigated whether the decrement results from lateral masking by manipulating the degree scenes shared the same frequency components with the objects. Scenes were filtered (low- or high-passed) at six cutoff frequencies (0.4, 0.7, 1.4, 2.8, 4, or 5.6 cpd) and objects were filtered (low- or high-passed) at 2 cpd. The results showed that when the object and the scene shared more spatial frequency band the identification performance became worse after viewing stimuli for 36 ms. These results supported that scene can produce the effect of lateral masking that reduces the performance of object identification. In Experiment 3, we used the same cutoff frequencies as in Experiment 2 to filter background and presented intact objects without filtering. Viewing duration was 36 ms. We examined whether scenes are beneficial by comparing performance with object identification in noise background where the frequency components were the same as in the scenes and lateral masking occurred in both types of background. The results showed that object identification in scene background was better than that in noise background. In addition, the scene benefit was eliminated when the low spatial frequency was removed from the scene. Taken together, the results supported that the low-spatial frequency of scene contexts is beneficial for object identification. However, objects must contain high spatial frequency components so that lateral masking within frequency channels does not lower identification performance. Activation of possible objects is beneficial only when details of objects can be integrated for identification.
Subjects
spatial frequency
object identification
scene perception
lateral masking
Type
thesis
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