Mirror-reflecting a picture of an object: what happens to the shape percept?

Although a two-dimensional picture never fully specifies the actual layout of the depicted three-dimensional scene, one is still able to make a three-dimensional interpretation. When a picture is mirror-reflected, the range of plausible scenes possibly corresponding with the depicted scene has not changed with respect to the original depiction. We were curious to find out whether the inherent picture ambiguities would be solved the same way or differently. Participants performed local attitude settings on three sets of pictures: (1) original pictures, (2) left-right mirrored pictures, and (3) up-down mirrored pictures. Pairwise comparison of the pictorial reliefs of the depicted object, reconstructed from the raw settings, revealed dissimilarities. The differences, however, could be drastically diminished by conducting an affine transformation correction taking into account not only the depths, but also the picture plane coordinates. The inherent ambiguities seemed thus to be solved differently between conditions. By factoring out different solutions to the ambiguities, the pictorial reliefs were found to be equivalent.     

Improving calibration over texts by providing standards both with and without idea-units

This study aims at improving calibration accuracy, which is the match between estimated performance and actual performance. In our experiment, one hundred and twenty-seven university students read texts and learned definitions. The students recalled these definitions during a test and made performance judgements. After recalling their definitions half of the students received full-definition standards, stating what the correct definition should have been. The other half of the students received idea-unit standards: The correct definition was parsed into units that had to be present. Providing standards improved calibration accuracy not only on current texts, but also on new, subsequent texts. Especially the calibration of low performing students benefitted from receiving both idea-unit and full-definition standards. Furthermore, over multiple texts, students who received idea-unit standards benefitted more than students receiving full-definition standards. This study is among the first to show the effect of standards on calibration on new texts and underscores the importance of self-testing.     

Visual rays are parallel

We show that human observers using monocular viewing treat the pencil of 'visual rays' that diverges from the vantage point as experientally parallel. This oddity becomes very noticeable in the case of wide-angle presentations, where the angle subtended by a pair of visual rays may be as large as the angular size of the display. In our presentations such angles subtended over 100 deg. There are various ways to demonstrate the effect; in this study we measure the attitudes of pictorial objects that appear to be situated in mutually parallel attitudes in pictorial space. Our finding is that such objects appear parallel if they are similarly oriented with respect to the local visual rays. This leads to 'errors' in the judgment of mutual orientations of up to 100 deg. Although this appears to be the first quantitative study of the effect, we trace it to qualitative reports by Helmholtz (late 19th century) and Kepler (early 17th century) as well as speculation by early authors (AD 500). The effect has apparently been noticed by visual artists from the late middle ages to the present day.     

Cast shadows in wide perspective

We investigated the apparent spatial layout of cast shadows up to very wide fields of view. We presented up to 130 degrees wide images in which two 'flat poles' were standing on a green lawn under a cloudless blue sky on a sunny day. The poles threw sharp cast shadows on the green, of which one was fixed. The observer's task was to adjust the azimuth of the shadow of the other pole such that it fitted the scene. The source elevation was kept constant. The two cast shadows are, of course, parallel in physical space, but generically not in the picture plane because of the wide perspective. We found that observers made huge systematic errors, indicating that, generically, they fail to account for these perspective effects. The systematic deviations could be well described by a weighted linear combination of the directions in the picture plane and in the physical space, with weights that depended on the positions of, and distance between, the poles.     

Improved effectiveness of cueing by self‐explanations when learning from a complex animation

A major problem in learning from instructional animations is that the complex perceptual and cognitive processing exceeds the learner's limited processing capacities. Although attention cueing might help learners in focusing on essential parts of an animation, previous studies have shown that it does not necessarily improve learning performance. This study investigated whether generating self‐explanations while studying a cued or an uncued animation might engage learners in cognitive activities necessary for learning. It was hypothesized that learning from a cued animation that reduces working memory load associated with searching for specific elements might be improved by generating self‐explanations, whereas self‐explaining with an uncued animation would have no positive effect on learning. The results confirmed the hypothesized interaction between cueing and self‐explaining. They suggest that self‐explanation enhances learning if visual cues are used to structure and highlight the essential parts of an animation. Copyright © 2010 John Wiley & Sons, Ltd.     

Does retrieval practice depend on semantic cues? Assessing the fuzzy trace account of the testing effect

Retrieval practice enhances long-term retention more than restudying; a phenomenon called the testing effect. The fuzzy trace explanation predicts that a testing effect will already emerge after a short interval when participants are solely provided with semantic cues in the final test. In the present study, we assessed this explanation by gradually reducing the surface features overlap between cues in the learning phase and the final recognition test. In all five experiments, participants in the control/word condition received as final test cues the same words as in the learning phase. The experimental final test cues consisted of scrambled words, words in a new context, scrambled words in a new context (Experiment 1), synonyms (Experiment 2), or images (Experiments 3, 4a, 4b). A short-term testing effect was only observed for the image final test cues. These results do not provide strong support for the fuzzy trace explanation of the testing effect.     

The effect of study time distribution on learning and retention: a Goldilocks principle for presentation rate

In 2 experiments, we investigated the effect of presentation rate on both immediate (5 min) and delayed (2 days) cued recall of paired associates. Word pairs were presented for a total of 16 s per pair, with presentation duration of individual presentations varying from 1 to 16 s. In Experiment 1, participants studied word pairs with presentation rates of 16 × 1 s, 8 × 2 s, 4 × 4 s, 2 × 8 s, or 1 × 16 s. A nonmonotonic relationship was found between presentation rate and cued recall performance. Both short (e.g., 1 s) and long (e.g., 16 s) presentation durations resulted in poor immediate and delayed recall, compared with intermediate presentation durations. In Experiment 2, we replicated these general findings. Moreover, we showed that the 4 s condition resulted in less proportional forgetting than the 1 s and the 16 s conditions.