Shapes Displayed with Durations in the Microsecond Range Do Not Obey Bloch's Law of Temporal Summation

2014

i-Perception

Self Cite

It is generally thought that the perceptual impact of a brief flash of light is determined by the quantity of photons the flash delivers. This means that only the total quantity of photons is important below a critical duration of about 30–100 ms. Recent findings have challenged this concept and the present work provides additional evidence that it is not correct. The first experiment reported here delivered a given quantity of photons in under 200 μs, either as a single threshold-intensity flash or as multiple flashes at the same intensity. The single flash was ineffective at eliciting recognition, but multiple flashes became progressively more effective as the number of flashes was increased. A second experiment varied the number of 10 μs flashes. The effectiveness of multiple flashes was far higher than would be expected on the basis of the total quantity of photons being delivered. The results of both experiments suggest that the brief transitions of intensity provided by the flashes are far more important than the quantity of photons. A final experiment examined the combined impact from two threshold-intensity flashes as the interstimulus interval was increased. The pair members were able to combine their influence for at least 100 ms. These results call for more attention to how very brief light flashes generate signals that convey image content.

Section: Introductionsupporting

confidence: 91%

Section: Introductionsupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Shape Recognition Elicited by Microsecond Flashes is Not Based on Photon Quantity

2014

i-Perception

Self Cite

“…This system was previously used to study recognition with a diverse inventory of 360 shapes, e.g., animals, vehicles, tools, and furniture (Greene & Ogden, 2013, Greene, 2013. The shapes were rendered as a continuous string of dots that marked the major contours of each shape, in particular the outer boundary, similar to a silhouette.…”

Section: Introductionmentioning

confidence: 99%

Recognition of letters displayed as briefly flashed dot patterns

Atten Percept Psychophys

Visani

2015

Self Cite

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.

Violation of Bloch's Law That Specifies Reciprocity of Intensity and Duration with Brief Light Flashes

2013

i-Perception

Self Cite

For more than a century researchers have been reporting that the visual impact of a very brief flash is determined by the quantity of photons that the flash delivers. This has been variously described as the Bunsen-Roscoe Law or Bloch's Law, often specified as reciprocity of intensity × duration. Prior research found no evidence for such reciprocity when microsecond-duration flashes from a light-emitting diode array were used to display the major contours of nameable shapes. The present work tested with flash durations ranging up to 100 ms and also found no reciprocity. This departure from classic principles might be due to the specific range of wavelengths of the light-emitting diodes and to a mesopic level of ambient light, which together would preclude activation of rods. The reciprocity of intensity and duration may only be valid with full dark adaptation and very dim flashes that activate rods.