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 ...

In pattern masking, the target and mask are presented at the same location and follow one another very closely in time. When the observer attends to the target, he or she must also attend to the mask, as the switching time for attention is quite slow. In a series of experiments, we present mask-target-mask sequences staggered in time and location (Cavanagh, Holcombe, & Chou, 2008) that allow pa...

The spacing of a fixed amount of study time across multiple sessions usually increases subsequent test performance*a finding known as the spacing effect. In the spacing experiment reported here, subjects completed multiple learning trials, and each included a study phase and a test. Once a subject achieved a perfect test, the remaining learning trials within that session comprised what is known...

Discussions about fertility in developed countries refer almost exclusively to the period Total Fertility Rate (TFR). We argue that the use of this indicator frequently leads to incorrect interpretations of period fertility levels and trends, resulting in distorted policy conclusions and, potentially, in misguided policies. We illustrate this with four policy-relevant examples, drawn from conte...