Probe methods were used to investigate whether the distribution of attention to the local or the global structure of a stimulus affects the detectability of different spatial frequencies. Four experiments are reported in which the detectability of threshold probe gratings of different spatial frequencies was measured while subjects analyzed either the local or the global information from a display. A relative shift in the detectability of low and high frequencies was observed. Low frequencies were facilitated during global processing and/or high frequencies were facilitated during local processing.