Complete mergeability and amodal completion.

When image fragments are taken to correspond to the visible portions of a single occluded object, the object is said to 'amodally complete' behind the occluder. Kellman and Shipley (Kellman, P. J., & Shipley, T. F. (1991). A theory of visual interpolation in objective perception. Cognitive Psychology, 23, 144-221) argued that when the virtual contour extensions of such image fragments subtend an obtuse or right angle, the contours are 'relatable' and therefore complete. However, edge and surface relatability are neither necessary nor sufficient for completion to be perceived (Tse, P. U. (1999) Volume completion. Cognitive Psychology). Evidence is offered that completion is not driven directly by image cues such as contour relatability, but is driven, rather, by intermediate representations, such as volumes that are inferred from global image cue relationships. Evidence suggests that several factors, none of which is necessary for amodal completion to occur, contribute to the perceived strength of amodal completion, including similarity of pattern or substance, proximity, and good volume continuation or complete mergeability. Two partially occluded volumes are completely mergeable when they can be extended into occluded space along the trajectory defined by their visible surfaces such that they merge entirely with each other. Mergeability is not measurable in the image because it describes an inferred relationship among volumes that must themselves be inferred from the image.     

Wakes and spokes: new motion-induced brightness illusions

Under certain conditions, high-contrast moving figures induce adjacent illusory regions, 'wakes' and 'spokes', which have contrast polarity opposite the inducing figures. In this paper we document properties of these novel phenomena. When the illusions are induced by a moving bar, spokes appear on the side of the bar closer to fixation and connect the bar to the fixation point, regardless of the momentary position of the bar or whether it is moving to the left or to the right. Although spokes often extend up to the fixation point, they never extend beyond it. This is not due to blocking of the spoke's spread by the fixation point, because in another experiment spokes extend directly through an intervening figure. Whereas spokes emanate from the end of a horizontally moving bar closest to fixation, wakes emanate from the end farthest from fixation. In contrast to spokes, wakes do not show a towards-fixation bias. Instead, the wake's end trails the position of the bar, like a ship's wake. The higher the bar velocity, the more the end of the wake appears to trail it, suggesting that wakes are caused by a process which spreads from the edge of moving figures. Wakes and spokes, as distinct illusions, should provide significant constraints on theories of human motion and brightness perception processes.     

Orthographic analogies and phonological priming: a comment on Bowey, Vaughan, and Hansen (1998)

J. A. Bowey, L. Vaughan, and J. Hansen (1998, Journal of Experimental Child Psychology, 68, 108-133) carried out two experiments on 6- and 7-year-old children's use of orthographic analogies in word reading. They reported that, following apparently stringent controls for phonological priming effects, beginning analogies (beak-bean) were more frequent in this age group than rime (beak-peak) analogies. From this, they concluded that beginning readers do not reliably use orthographic rimes in reading, even in the clue word task (p. 129). However, the clue word task was not used in this study. This comment highlights two problems with Bowey et al.'s paper. The first is a theoretical one, and the second is methodological. Firstly, Bowey et al. base their investigation on a misunderstanding of U. Goswami and P. E. Bryant's (1990, Phonological skills and learning to read, Hillsdale, NJ: Erlbaum) claims about the role of rhyme and analogy in beginning reading. Secondly, methodological weaknesses, in particular unintended intralist priming effects, seriously limit the conclusions that can be drawn from Bowey et al.'s booklet analogy task.     

A neuropsychological theory of positive affect and its influence on cognition.

Positive affect systematically influences performance on many cognitive tasks. A new neuropsychological theory is proposed that accounts for many of these effects by assuming that positive affect is associated with increased brain dopamine levels. The theory predicts or accounts for influences of positive affect on olfaction, the consolidation of long-term (i.e., episodic) memories, working memory, and creative problem solving. For example, the theory assumes that creative problem solving is improved, in part, because increased dopamine release in the anterior cingulate improves cognitive flexibility and facilitates the selection of cognitive perspective.     

Modeling stage-sequential change in ordered categorical responses

Although few would dispute the usefulness of looking at behavioral change from a stage-sequential perspective, until recently the lack of appropriate modeling techniques has hampered rigorous empirical tests of stage theories. In particular, for behavioral measurements that are ordinal, there is a need for methods that represent the underlying change processes in the form of qualitative and discontinuous shifts. This article introduces a stage-sequential ordinal model by postulating that at any point in time there are a finite number of latent stages. Panel members may shift among these stages over time. The authors show that the stage-sequential model provides a general approach for both the analysis of ordinal time-dependent data and tests of various competing theories and hypotheses about psychological change processes. An analysis of a 5-year study concerning attitudes toward alcohol consumption by teenagers is presented to illustrate the modeling approach.     

Labelled Resolution for Classical and Non-classical Logics

Resolution is an effective deduction procedure for classical logic. There is no similar "resolution" system for non-classical logics (though there are various automated deduction systems). The paper presents resolution systems for intuistionistic predicate logic as well as for modal and temporal logics within the framework of labelled deductive systems. Whereas in classical predicate logic resolution is applied to literals, in our system resolution is applied to L(abelled) R(epresentation) S(tructures). Proofs are discovered by a refutation procedure defined on LRSs, that imposes a hierarchy on clause sets of such structures together with an inheritance discipline. This is a form of Theory Resolution. For intuitionistic logic these structures are called I(ntuitionistic) R(epresentation) S(tructures). Their hierarchical structure allows the restriction of unification of individual variables and/or constants without using Skolem functions. This structures must therefore be preserved when we consider other (non-modal) logics. Variations between different logics are captured by fine tuning of the inheritance properties of the hierarchy. For modal and temporal logics IRS's are extended to structures that represent worlds and/or times. This enables us to consider all kinds of combined logics.     

The epidemiology of Wilson's disease in the German Democratic Republic and current problems from the viewpoint of population genetics

Between 1949 and Nov. 30, 1977 a total of 123 cases of Wilson's disease have been registered in the GDR. Using the available statistics the incidence rate of the disease is assumed to be about 2.9/100,000, the gene frequency approx. 0.53 per cent and the heterozygote incidence 1.05 per cent, supposing that the Hardy-Weinberg law applies to a large extent. Conclusions are drawn from the available material with a view to detection of the disease infuture and to genetic family counselling.     

Separate and joint scaling of perceived odor intensity ofn-butanol and hydrogen sulfide

To determine which combination of scaling method and experimental procedure is optimal for measuring perceived odor intensity, the intensity perception of one odorous substance was scaled both separately and together with a second odorous substance in the same session. The methods used were magnitude estimation with and without a standard reference and cross-modal matching with finger span. The results show that separate and joint scalings ofn-butanol and H₂S give identical scales, regardless of scaling method. Different results are obtained in magnitude estimations with a homoquality, a heteroquality, and no standard. From these results, one would not expect to find a single true power function independent of method. Cross-modal matching with finger span may be the best choice for odor intensity scaling, since it results in the widest response range, thereby giving the best resolution.