Recognition of letters displayed as briefly flashed dot patterns.

Complex shapes can be identified (named) when only the outer boundary of the shape is represented by discrete dots and with the dots being displayed for a duration lasting only a few microseconds (μs). This line of work is extended here to include recognition of letters with 10 μs flashes as a means to study visible persistence and information persistence. The first two studies were designed to assess visible persistence. Models were derived that quantified how recognition changed as a function of flash intensity. Then each letter was displayed twice, each at a near-threshold level of intensity and varying the interval between flashes. The second flash was able to boost the influence of the first flash for about 100 ms. This corresponds to the duration that a brief flash will remain visible, so these conditions likely were producing visible persistence. Information persistence was studied by manipulating dot density of the letter patterns. Recognition declined as the density of dots in each letter pattern was reduced. When two complimentary low-density samples were flashed, there was summation of their influence that declined to an asymptote in about 200 ms, and then remained above the one-flash control out to the maximum test interval of 1 s. The summation of high-salience, low-density dot patterns over such a long interval likely reflects both iconic memory persistence and access to working memory.