Discounting the effect of memory on repeated measures of beauty judgment

The intrinsic variance of beauty judgment is key to modeling beauty ratings. However, in repeated measures of beauty, observers surely make use of what they remember. To test how memory contributes to repeated beauty ratings, we asked participants to rate 75 arbitrarily named images (e.g., Fred). Initially, participants rated (1 to 7) how much beauty they felt from looking at a named image. Then participants completed two conditions. In the memory condition, participants saw only the name of an image and were asked to remember the image corresponding to that name and rate how much beauty they felt. In the repeat condition, they once again rated how much beauty they felt from looking at a named image. Lastly, in a memory check, participants tried to select which image was associated with a name. Only considering the correctly remembered trials (60%), we calculated the distribution of the differences between the initial beauty rating and that from either the memory condition or the repeat condition. The variance for the memory condition was more than double that of the repeat condition. Likewise, the initial beauty ratings predicted 84% of the variance in the repeat ratings but only 30% of the variance in the memory ratings. Cue combination studies report that observers typically combine cues by the optimal Bayesian rule: The combined reliability is the sum of the separate reliabilities for each cue, where reliability is one over variance. Assuming optimal combination of memory and immediate-perception judgment, we can discount the contribution of memory to estimate the variance of the immediate-perception judgment. Thus, in our paradigm the 0.83 variance of the repeated beauty rating corresponds to a 0.97 immediate-perception judgment variance (without memory). Overall, since there also was no significant difference in means, our results indicate that memory contributes little to repeated beauty ratings

A clinical test for visual crowding

Crowding is a major limitation of visual perception. Because of crowding, a simple object, like a letter, can only be recognized if clutter is a certain critical spacing away. Crowding is only weakly associated with acuity. The critical spacing of crowding is lowest in the normal fovea, and grows with increasing eccentricity in peripheral vision. Foveal crowding is more prominent in certain patient groups, including those with strabismic amblyopia and apperceptive agnosia. Crowding may lessen with age during childhood as reading speed increases. The range of crowding predicts much of the slowness of reading in children with developmental dyslexia. There is tantalizing evidence suggesting that the critical spacing of crowding indicates neural density (participating neurons per square deg) in the visual cortex. Thus, for basic and applied reasons, it would be very interesting to measure foveal crowding clinically in children and adults with normal and impaired vision, and to track the development of crowding during childhood. While many labs routinely measure peripheral crowding as part of their basic research in visual perception, current tests are not well suited to routine clinical testing because they take too much time, require good fixation, and are mostly not applicable to foveal vision. Here we report a new test for clinical measurement of crowding in the fovea. It is quick and accurate, works well with children and adults, and we expect it to work well with dementia patients as well. The task is to identify a numerical digit, 1-9, using a new “Pelli” font that is identifiable at tiny width (0.02 deg, about 1 minarc, in normal adult fovea). This allows quick measurement of the very small (0.05 deg) critical spacing in the normal adult fovea, as well as with other groups that have higher critical spacing. Preliminary results from healthy adults and children are presented

Influence of V/III molar ratio on the formation of In vacancies in InN grown by metal-organic vapor-phase epitaxy

We have applied a slow positron beam to study InN samples grown by metal-organic vapor-phase epitaxy with different V/III molar ratios (3300–24 000) and at different growth temperatures (550–625°C). Indium vacancies were identified in samples grown at V/III ratios below 4000. Their concentration is in the 10exp17cm−3 range. No strong dependence of vacancy concentration on the molar ratio was observed. At low V/III ratios, however, In droplets and vacancy clusters are formed near the substrate interface. The elevated growth temperature enhances the In vacancy formation, possibly due to limited sticking of In on the growth surface close to the decomposition temperature.Peer reviewe

Compensating point defects in 4He+ -irradiated InN

We use positron annihilation spectroscopy to study 2 MeV 4He+ -irradiated InN grown by molecular-beam epitaxy and GaN grown by metal-organic chemical-vapor deposition. In GaN, the Ga vacancies act as important compensating centers in the irradiated material, introduced at a rate of 3600 cm exp −1. The In vacancies are introduced at a significantly lower rate of 100cm−1, making them negligible in the compensation of the irradiation-induced additional n-type conductivity in InN. On the other hand, negative non-open volume defects are introduced at a rate higher than 2000cm exp −1. These defects are tentatively attributed to interstitial nitrogen and may ultimately limit the free-electron concentration at high irradiation fluences.Peer reviewe

Probing pictorial relief: from experimental design to surface reconstruction

The perception of pictorial surfaces has been studied quantitatively for more than 20 years. During this time, the “gauge figure method” has been shown to be a fast and intuitive method to quantify pictorial relief. In this method, observers have to adjust the attitude of a gauge figure such that it appears to lie flat on a surface in pictorial space. Although the method has received substantial attention in the literature and has become increasingly popular, a clear, step-by-step description has not been published yet. In this article, a detailed description of the method is provided: stimulus and sample preparation, performing the experiment, and reconstructing a 3-D surface from the experimental data. Furthermore, software (written in PsychToolbox) based on this description is provided in an online supplement. This report serves three purposes: First, it facilitates experimenters who want to use the gauge figure task but have been unable to design it, due to the lack of information in the literature. Second, the detailed description can facilitate the design of software for various other platforms, possibly Web-based. Third, the method described in this article is extended to objects with holes and inner contours. This class of objects have not yet been investigated with the gauge figure task

The design of the main accelerator for a pulsed positron beam

Abstract The pulsed positron beam at the Helsinki University of Technology is designed for the end energy of 3-30 keVand grounded target. This is achieved with a constant voltage acceleration followed by an adjustable deceleration. In the design of this accelerator-decelerator the possibility for electrical breakdowns and partial discharges must be eliminated. For designing the electrode and insulator structures for accelerator-decelerator configuration electric field simulations were carried out with the finite element analysis program. In this paper we present the design of the accelerator-decelerator and the results of the electric field simulations. The results of high voltage tests will also be presented and compared with the simulations.

Ventral extra-striate cortical areas are required for optimal orientation averaging

We examined the ability of a previously well-studied patient with visual agnosia to compute the average orientation of elements in visual displays. In a structural MRI study, we show that the lesion is likely to involve a variety of ventral extra-striate areas, including V2, V3 and V4; however, the lesion does not extend dorsally. Subsequently we show that some ability to compute average orientation is spared, though there are limitations on the ability to scale the averaging process as a function of the numbers of elements. The results suggest that some aspects of orientation averaging can be accomplished in spared regions of V1 but flexible averaging requires ventral extra-striate cortex

Substitution and pooling in crowding

Unless we fixate directly on it, it is hard to see an object among other objects. This breakdown in object recognition, called crowding, severely limits peripheral vision. The effect is more severe when objects are more similar. When observers mistake the identity of a target among flanker objects, they often report a flanker. Many have taken these flanker reports as evidence of internal substitution of the target by a flanker. Here, we ask observers to identify a target letter presented in between one similar and one dissimilar flanker letter. Simple substitution takes in only one letter, which is often the target but, by unwitting mistake, is sometimes a flanker. The opposite of substitution is pooling, which takes in more than one letter. Having taken only one letter, the substitution process knows only its identity, not its similarity to the target. Thus, it must report similar and dissimilar flankers equally often. Contrary to this prediction, the similar flanker is reported much more often than the dissimilar flanker, showing that rampant flanker substitution cannot account for most flanker reports. Mixture modeling shows that simple substitution can account for, at most, about half the trials. Pooling and nonpooling (simple substitution) together include all possible models of crowding. When observers are asked to identify a crowded object, at least half of their reports are pooled, based on a combination of information from target and flankers, rather than being based on a single letter

Planar coupling to high-Q lithium niobate disk resonators

We demonstrate optical coupling to high-Q lithium niobate disks from an integrated lithium niobate waveguide. The waveguides are made by proton exchange in X-cut lithium niobate substrate. The disks with diameter of 4.7 mm and thickness of 1 mm are made from commercial Z-cut lithium niobate wafers by polishing the edges into a spheroidal profile. Both resonance linewidth and cavity ringdown measurements were performed to calculate the Q factor of the resonator, which is in excess of 10(8). Planar coupling represents the most promising technique for practical applications of whispering gallery mode resonators

Letter processing and font information during reading: beyond distinctiveness, where vision meets design

Letter identification is a critical front end of the reading process. In general, conceptualizations of the identification process have emphasized arbitrary sets of distinctive features. However, a richer view of letter processing incorporates principles from the field of type design, including an emphasis on uniformities across letters within a font. The importance of uniformities is supported by a small body of research indicating that consistency of font increases letter identification efficiency. We review design concepts and the relevant literature, with the goal of stimulating further thinking about letter processing during reading