Frequency dependent object recognition A Bexter, T Stemmler |
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Biology, RWTH Aachen, Germany
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| Visual information in object recognition is selectively processed already at the retina. Magnocellular and parvocellular ganglion cells differ especially in spatial frequency tuning. Earlier research showed information from low-pass filtered pictures reaches cortical areas associated with decision making faster than high frequency information [Bar et al, 2006 PNAS, 103(2), 449 – 454]. Here we present data, how the recognition speed and accuracy in ultra-fast object recognition is influenced when the stimuli are frequency-filtered through a wavelet-transformation and presented from low frequencies to high frequencies and in opposite direction. Observers viewed images containing an animal as targets against distractor pictures of natural scenes without an animal. In the first part we presented pictures with predefined frequency components (low, middle, high) for 15 ms on a 200 Hz Monitor in a saccadic 2AFC task to establish baseline performance. In the second part of the experiment observers viewed three consecutive frames, containing different spatial-frequency in each frame. All six possible permutations for low, middle and high were tested separately. The comparison of the presentation order revealed a significant advantage for presentation sequence from low-to-high over high-to-low in performance. Presentation in opposite order to natural arrival times may disturb perception. |
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