Misalignment effects in 3-D versions of Poggendorff displays

Strong misalignment effects are found in three-dimensional (3-D) versions of Poggendorff displays viewed binocularly. The components of the standard 2-D Poggendorff figure—the parallels and the oblique segments—were presented in 3-D depth as a flat rectangular object with occluding edges and an oblique line situated behind the object. Three experiments investigated the misalignment effects under three different observation instructions: Subjects were told to look at the oblique (Experiment 1), at the rectangle (Experiment 2), or at the background (Experiment 3). Experiments 1 and 2 examined the effects on judgments of alignment of varying the distance in depth that separates the oblique from the rectangle. Experiment 3 examined the effects of varying the distance between the fixated background and the 3-D Poggendorff figure. Both standard and reversed misalignment effects were obtained. When the viewing condition produces crossed disparity for the oblique, perceived misalignment occurs in the usual Poggendorff direction, but it is reversed with uncrossed disparity. Moreover, the amount of misalignment is related to the amount of disparity, and it can be much stronger than is usual in the 2-D versions of the Poggendorff. The misalignment effects can be explained by binocular integration to produce a single cyclopean image.     

Quantitative and qualitative analyses of clock drawings in Alzheimer's and Huntington's disease.

Although visuoconstructive impairment has been reported in both Alzheimer's (DAT) and Huntington's (HD) disease, there is little knowledge concerning how this cognitive deficit differs quantitatively and qualitatively in these two progressive dementias. To address this issue, the present study compared performances on the Clock Drawing Test (CDT: command and copy) of 25 DAT patients, 25 equally demented HD patients, and 25 elderly normal controls (NC). In the command condition, both patients groups were significantly impaired compared to the NC group. Although there was no significant difference between DAT and HD patients' total quantitative scores, a qualitative error analysis revealed a number of dissociations between the two patient groups. Graphic difficulties, very common in HD patients, were virtually absent in DAT patients; in contrast, conceptual errors were almost exclusively seen in DAT patients and were related to the severity of their dementia. Perseveration and "stimulus-bound" responses were also more frequent in DAT patients, and both groups made visuospatial errors. In the copy condition, the DAT, but not the HD, patients evidenced a marked improvement in performance. These results indicate that while both DAT and HD patients have significant visuoconstructive difficulties even in the early stages of their disorders, the specific cognitive processes underlying their quantitative impairments are quite different. It is possible that the DAT patients' conceptual errors are yet another indicator of the deterioration of their semantic knowledge.     

Reflections upon charitable giving: A comparison of individuals from business, ‘manual’ and professional backgrounds

This paper compares three groups of individuals in their beliefs about charitable giving. Focusing upon their preferences for different kinds of needy recipients, the paper compares the views of 49 people from (a) business, (b) professional and (c) ‘manual’ backgrounds. Their justifications of need provided the basis for comparisons on the basic themes of emotional response to requests for funds, to local versus overseas aid and to the relative roles of charity and state provision. It is argued that distinctions between the groups show the need to examine specific beliefs as well as generally held ideologies about charity. In addition, a further comparison of the groups is used to argue that they exemplify differences in the actual form of the gift relationship. These differences in form show the importance of examining charitable giving within specific social contexts, as well as with reference to the various ways of raising funds.     

Adaptation to sensory-motor temporal misalignment: instrumental or perceptual learning?

Sensory-motor delays vary over the course of development and under different environmental conditions. Previous research has shown that humans can compensate for the resulting temporal misalignment while performing sensory-motor tasks (e.g., Cunningham, Billock, & Tsou, 2001a), but remains silent on the question of whether perceptual learning-similar to that involved in adaptation to spatial misalignment (e.g., Redding & Wallace, 1993) and in adaptation to purely intersensory misalignment (e.g., Fujisaki, Shimojo, Kashino, & Nishida, 2004)-is also involved in this adaptive response. Following an attempted replication of Cunningham et al.'s (2001a) study in a preliminary experiment, we present in this paper two experiments that demonstrate that after-effects of adaptation to temporal misalignment do not spontaneously decay. The literature on adaptation to spatial misalignment suggests that, while instrumental learning spontaneously decays in the absence of reinforcement, perceptual learning persists. Therefore our results are consistent with adaptation being effected through perceptual learning.     

Defending the Possibility of Knowledge

In this paper, I propose a solution to Fitch’s paradox that draws on ideas from Edgington (Mind 94:557–568, 1985), Rabinowicz and Segerberg (1994) and Kvanvig (Noûs 29:481–500, 1995). After examining the solution strategies of these authors, I will defend the view, initially proposed by Kvanvig, according to which the derivation of the paradox violates a crucial constraint on quantifier instantiation. The constraint states that non-rigid expressions cannot be substituted into modal positions. We will introduce a slightly modified syntax and semantics that will help underline this point. Furthermore, we will prove results about the consistency of verificationism and the principle of non-omniscience by model-theoretical means. Namely, we prove there exists a model of these principles, and delineate certain constraints they pose on a structure in which they are true.     

Spatial coordinates and reading: Comments on Monk (1985)

Subjects are able to process some texts when they are presented, word-by-word, in a single physical location. As differential spatial information is not available in this task, Monk (1985a) argues that it need not be derived in normal reading. We suggest this conclusion is unwarranted, because subjects make large and very accurate regressive saccades to regions of previously fixated text. Without a representation of spatial coordinates this should not occur.