Representation of spatial structure in reaching to a visual target.

Reaches made without feedback to positions on an object's surface reflect the spatial form of the surface. In Experiment 1, the reaching pattern varied with the stimulus surface's spatial attributes, consistent with a point-by-point perceptual representation of the surface. In Experiment 2, systematic reaching errors were determined solely by target position regardless of surface structure, implying a highly consistent representation of location. In Experiment 3, illusory slant was imparted to a surface by an aniseikonic lens. Individual variations in directly judged slant were reflected in the reaching pattern, implying organization of local perceptual representation of location and global perception of spatial attributes of the stimulus into a coherent structure.     

The precision of velocity discrimination across spatial frequency

The precision of velocity coding for moving stimuli of different spatial frequencies was assessed by measuring velocity discrimination thresholds for a 1-c/deg grating paired with a grating whose spatial frequency ranged from 0.25 to 4 c/deg and for grating pairs of the same spatial frequency (0.25, 1, and 4 c/deg). The gratings always moved upward, with velocities ranging from 0.5 to 16 deg/sec, Velocity discrimination was as precise for stimuli that varied in spatial frequency by: ±2 octaves (0.25 vs. 1 c/deg and 4 vs. 1 c/deg) as for stimuli of the same spatial frequency, for specific ranges of velocity that depended on the spatial and, therefore, the temporal frequencies of the stimuli. Compared with a 1-c/deg grating, the perceived velocity of 4-c/deg gratings was about 1.3 times faster and that of 0.25-c/deg gratings was about 1.3 times slower. Although these perceived velocity biases imply variation of velocity-signal processing among spatial frequency channels, the discrimination results indicate that the motion-sensing system can compare signals across different spatial frequency channels to make fine velocity discrimination within appropriate temporal frequency limits.     

The compatibility of spatial and non-spatial relationships

This experiment reverses the procedure used by Hedge and Marsh (1975) who obtained two-choice RTs to a relevant stimulus attribute (colour) in the presence of an irrelevant attribute (location). On the basis of their finding that RT was faster when the colour and location of the correct response button were both the same, or both different from that of the stimulus, they concluded that performance is facilitated where the same logical process ‘same’ or ‘alternative’ can be applied to both attributes. The ‘Simon effect’ it was suggested may be explained by this process.Earlier work by the author had suggested performance is facilitated where the same recording rule applies to all the spatial relations in the task. Performing Hedge and Marsh's experiment with location as the relevant attribute failed to replicate their finding. This result limits the generality of their explanation to tasks where spatial relationships are the ‘irrelevant’ variable.     

Pattern structure and relational discrimination learning.

McGonigle and Jones take exception to Dodwell's explanation of anomalous transfer (AT) as the outcome of relational discriminations among a set of stimulus patterns which vary along a single dimension of orientational salience, from 'horizontal' to 'vertical'. In particular they do not think that the continuum is generated by units with Hubel-and-Wiesel type retinal receptive fields. Instead, they invoke Garner's notions about stimulus structure to explain Dodwell's results, as well as their own finding of two situations where AT fails to occur. It seems that McGonigle and Jones missed the point of the relational discrimination explanation of AT. In fact, it is shown that AT is not predicted by this model for the conditions in which they failed to obtain it. The relational model makes definite predictions about conditions under which AT will occur; as this is not true of their invocation of Garner's ideas, the former is to be preferred. Whether or not outputs are coded by Hubel-and Wiesel type units is not particularly relevant to the main point, that AT is a result of relational learning. In fact, the model is an instance of how structure, in Garner's sense, can be generated.     

The discrimination of structure in vectorgraphs: Local and global effects

Many recent electrophysiological studies have demonstrated specificity for orientation and position tuning in single units of the visual system. Psychophysical investigations have produced complementary evidence for orientation and position coding in vision which is usually interpreted in terms of the underlying neuronal properties. To date, no studies have endeavored to relate such “local” receptive field response profiles to more “global” or field-specific aspects of the input signal. In a series of experiments, we have investigated orientation/position sensitivity as a function of general orientation and position rules governing line element, or “vectorgraph,” displays. We have discovered with such vectorgraph images that individual element acuities are determined by the field structures present. These results show that there are specific “top-down” components even to basic orientation/position coding in the visual system     

The effect of location on the discrimination of spatial vibrotactile patterns

The present study examined whether the locations of patterns on the skin affected the ability to process information about their shapes. In Experiment 1, pairs of spatial vibrotactile patterns, using the array from the Optacon, were presented sequentially to subjects’ left index fingerpads. The location of each pattern in a pair was varied randomly among four locations on the skin. The subjects responded “same” or “different” on the basis of the shapes of patterns, regardless of their locations. Discrimination accuracy was highest and response time fastest when patterns occupied identical locations (ILs), and performance suffered with increasing distance between patterns. In Experiment 2, pairs were presented to corresponding points or to noncorresponding points on separate fingerpads. When patterns occupied corresponding points on separate fingers, accuracy was lower than when patterns occupied ILs on a single finger, but higher than when patterns occupied noncorresponding points on separate fingers. The results suggested that discriminability declined partly because patterns did not occupy ILs, and partly because separate locations had different densities of innervation.     

Coping with ambiguity and uncertainty in patient-physician relationships: III. Negotiation

Since beliefs, interests, needs and values vary among individuals, potential for conflict or dispute exists in all areas of human endeavor, including a patient-physician relationship. Conflict- or dispute-resolution requires diligent and directed negotiation, which ideally is amicable, efficient, and sustainable, if the participants acknowledge the identity, individuality, and integrity of all parties involved. In this essay a concept ofprincipled negotiation is extrapolated to a patient-physician relationship and is exemplified by a case study. In addition, the validity of a concept oftract two diplomacy is discussed, relevant from the perspective of strained or fractured primary relationships.     

Stimulus structure, discrimination, and interference.

Subjects learned lists of consonant trigram word pairs varying in intralist formal stimulus similarity. On test trials, subjects were tested with all but one stimulus, then presented either the missing stimulus or one previously tested. Subjects had to correctly identify this stimulus, then recall its associated word. Both recall and recognition performance varied with the difficulty of discovering and utilizing a discriminated element. However, when subjects were instructed as to list structure, recall was improved without improvement in recognition in one condition, and recognition was improved without recall in another. This indicates that stimulus discrimination is neither necessary nor sufficient to reduce intralist interference.     

Apparent duration and spatial structure.

In three experiments, we investigated the relative perceived duration of a full bandwidth image and a set of high- and lowpass filtered images of a scene, briefly presented on a visual display unit. In Experiment 1, the various images were compared with each other, using a paired comparison method. All images were presented for 40 msec, and observers were asked to judge which of each pair of images had the longest duration. The results showed that images containing a wide spatial frequency bandwidth were judged to be of longer duration than were images of a narrower bandwidth, regardless of whether the latter were high- or lowpass filtered. In Experiment 2, a 40-msec presentation of each of the images was compared with a presentation of a probe that was 20, 40, 60, or 80 msec in duration. Observers again judged which of each pair of images had the longest duration. The results were very similar to those of Experiment 1, with wide bandwidth images being judged to be of longer duration than were narrow bandwidth images. In Experiment 3, instead of comparing the various filtered versions of the image with each other, we attempted to obtain a direct measure of perceived duration by comparing a flashing LED to a 40-msec flash of a subset of the images used in the previous experiments. The observers' task was to adjust the duration of the LED flash to match the perceived duration of each image.(ABSTRACT TRUNCATED AT 250 WORDS)     

Sex and race discrimination resulting from manager-client relationships: Applying the rational bias theory of managerial discrimination

Rational bias theory predicts that discrimination may be situationally influenced by circumstances in which a show of bias seems likely to be rewarded or punished by others. This study applies the theory in an examination of managerial sex and race discrimination in situations in which normative or unusual signals are given. In agreement with rational bias theory, the participants, acting in the role of managers, indicated that they would be less likely to discriminate in personnnel decisions with cues indicating that discrimination might not be needed or wanted. The results are interpreted as supportive of rational bias theory and as useful for the design of new policies aimed at ending discrimination. The findings also suggest that the importance of discrimination against blacks of both sexes in management has been widely ignored.     

Discrimination of structure: I. Implications for connectionist theories of discrimination learning

In each of 4 experiments animals were given a structural discrimination task that involved visual patterns composed of identical features, but the spatial relations among the features were different for reinforced and nonreinforced trials. In Experiment 1 the stimuli were pairs of colored circles, and pigeons were required to discriminate between patterns that were the mirror image of each other. A related task was given to rats in Experiment 2. Subjects solved these discriminations. For Experiment 3, some pigeons were given a discrimination similar to that used in Experiment 1, which they solved, whereas others received a comparable task but with 3 colored circles present on every trial, which they failed to solve. The findings from Experiment 3 were replicated in Experiment 4 using different patterns. The results are difficult to explain by certain connectionist theories of discrimination learning, unless they are modified to take account of the way in which compound stimuli are structured.     

Semantic distance in memory structure: The retrieval of conceptual relationships

Four experiments are described which aim to distinguish the relative contributions of measures of semantic distance based on formal and normative criteria. Experiment I replicates a previous finding by Collins and Quillian (1969) that sentence confirmation RTs support a hierarchically-organised memory model. Experiments II and III minimised the role of syntactic processes and examined the times taken to “see the relationship” between pairs of concepts. The results also supported a hierarchical model but cast doubt upon the formal distinction between superset and property relationships. Experiment IV showed similar results using only property relationships of the “has” form. Multiple regression analyses of the data indicate that “number of intervening links” is a more consistent predictor of RT than “associative” measures of semantic relatendness and confirm strong linearity effects consistent with a hierarchical model of storage.     

Flexible visual processing of spatial relationships

Visual processing breaks the world into parts and objects, allowing us not only to examine the pieces individually, but also to perceive the relationships among them. There is work exploring how we perceive spatial relationships within structures with existing representations, such as faces, common objects, or prototypical scenes. But strikingly, there is little work on the perceptual mechanisms that allow us to flexibly represent arbitrary spatial relationships, e.g., between objects in a novel room, or the elements within a map, graph or diagram. We describe two classes of mechanism that might allow such judgments. In the simultaneous class, both objects are selected concurrently. In contrast, we propose a sequential class, where objects are selected individually over time. We argue that this latter mechanism is more plausible even though it violates our intuitions. We demonstrate that shifts of selection do occur during spatial relationship judgments that feel simultaneous, by tracking selection with an electrophysiological correlate. We speculate that static structure across space may be encoded as a dynamic sequence across time. Flexible visual spatial relationship processing may serve as a case study of more general visual relation processing beyond space, to other dimensions such as size or numerosity.     

The measurement of cyberbullying: dimensional structure and relative item severity and discrimination

In relation to a sample of 1,092 Italian adolescents (50.9% females), the present study aims to: (a) analyze the most parsimonious structure of the cyberbullying and cybervictimization construct in male and female Italian adolescents through confirmatory factor analysis; and (b) analyze the severity and the discrimination parameters of each act using the item response theory. Results showed that the structure of the cyberbullying scale for perpetrated and received behaviors in both genders could best be represented by a monodimensional model where each item lies on a continuum of severity of aggressive acts. For both genders, the less severe acts are silent/prank calls and insults on instant messaging, and the most severe acts are unpleasant pictures/photos on Web sites, phone pictures/photos/videos of intimate scenes, and phone pictures/photos/videos of violent scenes. The items nasty text messages, nasty or rude e-mails, insults on Web sites, insults in chatrooms, and insults on blogs range from moderate to high levels of severity. Regarding the discrimination level of the acts, several items emerged as good indicators at various levels of cyberbullying and cybervictimization severity, with the exception of silent/prank calls. Furthermore, gender specificities underlined that the visual items can be considered good indicators of severe cyberbullies and cybervictims only in males. This information can help in understanding better the nature of the phenomenon, its severity in a given population, and to plan more specific prevention and intervention strategies.