Stereological methods for serial sections traditionally assume that the sections are exactly equally spaced. In reality, the spacing and thickness of sections can be quite irregular. This may affect the validity and accuracy of stereological techniques, especially the Cavalieri estimator of volume. We present a new formula for the accuracy of the Cavalieri estimator that includes the effect of ...

The relationship between species richness and the occupation of niche space can provide insight into the processes that shape patterns of biodiversity. For example, if species interactions constrained coexistence, one might expect tendencies toward even spacing within niche space and positive relationships between diversity and total niche volume. I use morphological diversity of passerine bird...

Spatial order is the organizing principle of the visual areas in the brain. But to what extent does this spatial mapping help us see where things are? Observers trained to perfectly recall the spatial order of seven items presented simultaneously for 5 s were asked to report their order when flashed for only 150 ms. We found that the capacity for perceiving the order of these brief stimuli was ...

We measured the supernumerary spacing parameter of the first- and second-order rainbows of two glass rods, each having an approximately elliptical cross section, as a function of the rod's rotation angle. We attribute large fluctuations in the supernumerary spacing parameter to small local inhomogeneities in the rod's refractive index. The low-pass filtered first-order rainbow experimental data...

Does varying the spacing of repetitions over intervals as long as I week affect recall? The answer from three experiments is yes. Subjects incidentally processed words repeated within a single list and words repeated in separate lists at list spacings of up to I week. Memory was tested by free recall shortly after the second presentations or after retention intervals of up to I week. Recall of ...