Speed of processing and stimulus complexity in low-frequency and high-frequency channels.

Studies of the microgenesis of perception led to the hypothesis that global aspects of objects are processed faster than their details. If one starts with the assumption that low-frequency information of objects corresponds to the global, and high-frequency information to the local aspects, recognising objects should rely at first on information from the low-frequency channels and afterwards from that of the high-frequency channels. The priming paradigm provides a mean of investigating experimentally the temporal availability of low-frequency and high-frequency information in object perception. In the experiments subjects had to respond to target objects preceded either by related or by unrelated priming stimuli, which consisted of low-pass-filtered and high-pass-filtered versions of the objects. With the influence of stimulus complexity controlled, pictures of objects were chosen that varied in the number of intensity changes in the high-frequency components, with those of the low-frequency components kept constant. The exposure duration of each prime was varied between 40 and 100 ms. The results indicated that target identification only profits more from low-frequency than from high-frequency primes if the high-frequency information has a high level of complexity. If the number of intensity changes in the high-frequency components of the prime is low, target identification is most strongly facilitated. The results are discussed in terms of models which focus on organising principles at different scales.