The roles of altitude and fear in the perception of height.

Previous research on perceiving spatial layout has found that people often exhibit normative biases in their perception of the environment. For instance, slant is typically overestimated and distance is usually underestimated. Surprisingly, however, the perception of height has rarely been studied. The present experiments examined the perception of height when viewed from the top (e.g., looking down) or from the bottom (e.g., looking up). Multiple measures were adapted from previous studies of horizontal extents to assess the perception of height. Across all of the measures, a large, consistent bias was found: Vertical distances were greatly overestimated, especially from the top. Secondary findings suggest that the overestimation of distance and size that occurs when looking down from a high place correlates with reports of trait- and state-level fear of heights, suggesting that height overestimation may be due, in part, to fear. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of handedness and reachability on perceived distance.

Previous research has suggested that perceived distances are scaled by the action capabilities of the body. The present studies showed that when “reachability” is constrained due to a difficult grasp required to pick up an object, perceived distance to the object increases. Participants estimated the distances to tools with handle orientations that made them either easy or difficult to grasp with their dominant and nondominant hands. Right-handed participants perceived tools that were more difficult to grasp to be farther away than tools that were easier to grasp. However, perceived distance did not differ in left-handed participants. These studies suggest that, when reaching toward a target, the distance to that target is scaled in terms of how far one can effectively reach, given the type of reaching posture that is executed. Furthermore, this effect is modulated by handedness. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Expertise and category-based induction.

The authors examined inductive reasoning among experts in a domain. Three types of tree experts (landscapers, taxonomists, and parks maintenance personnel) completed 3 reasoning tasks. In Experiment 1, participants inferred which of 2 novel diseases would affect "more other kinds of trees" and provided justifications for their choices. In Experiment 2, the authors used modified instructions and asked which disease would be more likely to affect "all trees." In Experiment 3, the conclusion category was eliminated altogether, and participants were asked to generate a list of other affected trees. Among these populations, typicality and diversity effects were weak to nonexistent. Instead, experts' reasoning was influenced by "local" coverage (extension of the property to members of the same folk family) and causal-ecological factors. The authors concluded that domain knowledge leads to the use of a variety of reasoning strategies not captured by current models of category-based induction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Grasping objects by their handles: A necessary interaction between cognition and action.

Research has illustrated dissociations between "cognitive" and "action" systems, suggesting that different representations may underlie phenomenal experience and visuomotor behavior. However, these systems also interact. The present studies show a necessary interaction when semantic processing of an object is required for an appropriate action. Experiment 1 demonstrated that a semantic task interfered with grasping objects appropriately by their handles, but a visuospatial task did not. Experiment 2 assessed performance on a visuomotor task that had no semantic component and showed a reversal of the effects of the concurrent tasks. In Experiment 3, variations on concurrent word tasks suggested that retrieval of semantic information was necessary for appropriate grasping. In all, without semantic processing, the visuomotor system can direct the effective grasp of an object, but not in a manner that is appropriate for its use. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Coding spatial variations in faces and simple shapes: a test of two models

Faces all have the same basic elements in the same overall arrangement, and must be discriminated using variations in this shared configuration. An efficient way to represent these variations would be to code how each configuration differs from an average face (norm-based coding model). Alternatively, configurations could be represented simply by coding their absolute values in some coordinate system (absolute coding model). The two models differ in the variables they predict will influence an image's recognizability. Absolute coding predicts that recognizability will depend on an image's distinctiveness and degree of distortion from its veridical target. Norm-based coding predicts that recognizability will also depend on the way the image differs from a norm or average face, namely its distance from the norm and/or its degree of displacement from the norm-deviation vector for the target. We determined the effects of these four critical variables on recognition of undistorted (veridical) images, caricatures, anticaricatures and 'lateral' distortions of famous faces (Experiment 1), newly learned faces (Experiment 2), and simple shapes that also share a configuration (Experiment 2). The results favored absolute coding of both faces and shapes, and indicate that caricatures derive their power from their distinctiveness.     

Temporal pattern of cysteine endopeptidase (cathepsin B) expression in cartilage and synovium from rabbit knees with experimental osteoarthritis: gene expression in chondrocytes in response to interleukin-1 and matrix depletion

OBJECTIVE: To determine the temporal pattern of expression of cathepsin-B in chondrocytes and synovium in experimental osteoarthritis, and to determine possible mechanisms for upregulation and secretion of cathepsin-B from chondrocytes. METHODS: Experimental osteoarthritis was induced with partial medial meniscectomy (PM); sham operated (SH) and normal (N) rabbits were used as controls. Cathepsin-B mRNA expression was assessed with northern blotting with a 32P labelled cDNA probe. Cathepsin-B was measured in conditioned media or cell extracts using a fluorogenic substrate Z-Arg-Arg-AMC. Chondrocyte monolayers were used to determine cathepsin-B expression in response to interleukin-1 beta (IL-1 beta). Cartilage explants were used to test the effect of matrix depletion on cathepsin-B release. RESULTS: Chondrocytes obtained from experimental osteoarthritis knees did not show cathepsin-B mRNA upregulation. However, isolated chondrocytes secreted cathepsin-B into the culture medium. Enzyme release was significantly higher at 8 weeks relative to controls, but not at 12 weeks or 4 weeks. Enzyme released from synovium was significantly higher in PM group compared with SH group at 4 and 8 weeks. IL-1 beta was ineffective in upregulating steady state cathepsin-B mRNA in chondrocytes; however, it upregulated the intracellular enzyme, and this was blocked with cycloheximide. Enzymatic depletion of cartilage matrix after exposure of explants to IL-1 resulted in release of significantly higher amounts of cathepsin-B into the medium by matrix depleted chondrocytes compared with intact explants. CONCLUSIONS: In experimental osteoarthritis, cathepsin-B is upregulated in synovial tissue during the early degenerative phase. Progression of experimental osteoarthritis is accompanied by upregulation of cathepsin-B in cartilage. Cartilage and synovial cathepsin-B levels decline as experimental osteoarthritis advances to more degenerative states. IL-1 upregulates intracellular cathepsin-B by increasing cathepsin-B protein synthesis; it is not an effective stimulus for enzyme secretion. Depletion of cartilage matrix during progression of experimental osteoarthritis may contribute to secretion of cathepsin-B and perpetuation of cartilage destruction.     

Normalization of discrete planar objects

The case is made for normalization of discrete planar objects prior to comparison with test objects and an expression for normalization is derived using a Euclidean distance function based on the underlying continuous boundaries of the objects and their prototypes. The results are given in both the spatial and the frequency domain; an analysis of errors due to the quantization introduced by using a discrete grid is also given.     

Understanding natural dynamics.

When making dynamical judgments, people can make effective use of only one salient dimension of information present in the event. The adequacy of dynamical judgments depends on the degree of dimensionality that is both inherent in the physics of the event and presumed to be present by the observer. There are two classes of physical motion contexts in which objects may appear. In the simplest class, there exists only one dynamically relevant object parameter: the position over time of the object's center of mass. In the other class of motion contexts, there are additional object attributes, such as mass distribution and orientation, that are of dynamical relevance. A survey of commonsense understandings showed that people are relatively accurate when specific dynamical judgments can be accurately based on a single information dimension; however, erroneous judgments are pervasive when simple motion contexts are misconstrued as being multidimensional, and when multidimensional quantities are the necessary basis for accurate judgments. (PsycINFO Database Record (c) 2010 APA, all rights reserved)