Identification of everyday objects on the basis of fragmented outline versions

Although Attneave (1954 Psychological Review 61 183 193) and Biederman (1987 Psychological Review 94 115-147) have argued that curved contour segments are most important in shape perception, Kennedy and Domander (1985 Perception 14 367-370) showed that fragmented object contours are better identifiable when straight segments are shown. We used the set of line drawings published by Snodgrass and Vanderwart (1980 Journal of Experimental Psychology: Human Learning and Memory 6 174-215), to make outline versions that could be used to investigate this issue with a larger and more heterogeneous stimulus set. Fragments were placed either around the 'salient' points or around the midpoints (points midway between two salient points), creating curved versus relatively straight fragments when the original outline was fragmented (experiment 1), or angular and straight fragments when straight-line versions were fragmented (experiment 2). We manipulated fragment length in each experiment except the last one, in which we presented only selected points (experiment 3). While fragmented versions were on average more identifiable when straight fragments were shown, certain objects were more identifiable when the curved segments or the angles were shown. A tentative explanation of these results is presented in terms of an advantage for straight segments during grouping processes for outlines with high part salience, and an advantage for curved segments during matching processes for outlines with low part salience.     

Local contextual cuing in visual search

Previous research has indicated that covariations between the global layout of search displays and target locations result in contextual cuing: the global context guides attention to probable target locations. The present experiments extend these findings by showing that local redundancies also facilitate visual search. Participants searched for randomly located targets in invariant homogenous displays, i.e., the global context provided information neither about the location nor about the identity of the target. The only redundancy referred to spatial relations between the targets and certain distractors: Two of the distractors were frequently presented next to the targets. In four of five experiments, targets with frequent flankers were detected faster than targets with rare flankers. The data suggest that this local contextual cuing does not depend on awareness of the redundant local topography but needs the redundantly related stimuli to be attended to.     

Bayesian inference for psychology,part IV: parameter estimation and Bayes factors

In the psychological literature, there are two seemingly different approaches to inference: that from estimation of posterior intervals and that from Bayes factors. We provide an overview of each method and show that a salient difference is the choice of models. The two approaches as commonly practiced can be unified with a certain model specification, now popular in the statistics literature, called spike-and-slab priors. A spike-and-slab prior is a mixture of a null model, the spike, with an effect model, the slab. The estimate of the effect size here is a function of the Bayes factor, showing that estimation and model comparison can be unified. The salient difference is that common Bayes factor approaches provide for privileged consideration of theoretically useful parameter values, such as the value corresponding to the null hypothesis, while estimation approaches do not. Both approaches, either privileging the null or not, are useful depending on the goals of the analyst.     

On the development of perfectionism in adolescence: Perceived parental expectations predict longitudinal increases in socially prescribed perfectionism

Adolescence is regarded a key period when individual differences in perfectionism develop. Yet, so far only a few longitudinal studies have investigated the development of perfectionism in adolescents. Using a longitudinal correlational design with 381 adolescents aged 15–19 years, the present study investigated whether perceived parental expectations and criticism predicted longitudinal increases in self-oriented and socially prescribed perfectionism over 7–9 months. Results showed that perceived parental expectations predicted longitudinal increases in socially prescribed perfectionism: Adolescents who perceived that their parents had high expectations of them at Time 1, showed increased socially prescribed perfectionism from Time 1 to Time 2 compared to adolescents who did not perceive their parents having such high expectations. No such effect was found for self-oriented perfectionism. The findings provide supportive evidence for the social expectations model of the development of perfectionism regarding socially prescribed perfectionism, but not self-oriented perfectionism. Implications of this finding for the understanding of the development of perfectionism and future studies are discussed.     

Honderich,Davidson, and the question of mental holism

Honderich's defence of aspects of his correlationist theory against many objections actually or likely to be raised today, in particular from the point of view of Davidson's anomalous monism and psychological holism, is accepted as largely successful. But it is suggested that, even if Davidson's theory is wrong‐headed, another kind of holism, more deeply ontological and less linguistic, regarding the mental seems to be true, and presents difficulties for Honderich's correlationism. Finally, it is contended that a panpsychist kind of identity theory escapes his strictures on identity theories and is probably true; however, the identity is, in virtue of certain synthetic necessities about the course of a stream of consciousness, either only between particular mental and physical events (and thus anomalously monist in Davidson's sense), or if it holds also between types of mental and of brain event then certain quite striking consequences follow as to the character of the fullest possible explanation of what goes on in the brain.     

Application of the rubber hand illusion paradigm: comparison between upper and lower limbs

The “rubber hand illusion (RHI)” is a perceptual illusion, which allows the integration of artificial limbs into the body representation of a person by means of combined visual and tactile stimulation. The illusion has been frequently replicated but always concerning the upper limbs. The present study verified an analog illusion that can be called the “rubber foot illusion” (RFI). In a conjoint experiment using both a rubber hand and a rubber foot, brushstrokes were applied to the respective real and rubber limb placed alongside the real one. However, only the artificial limb’s handling was visible. The brushstrokes were given either synchronously, with a delay of ±0.5 s, or without tactile stimulation of the real limb. Questionnaire data and the proprioceptive drift towards the rubber limb (determined by calling on the subjects to show where they locate their unseen limb) defined the illusion strength. Results revealed that the illusion was induced in both limbs with comparable strength, but only in the synchronous condition.     

Children's voluntary exploration and preference for tactually presented nonsense shapes differing in complexity

This study represents an extension of research on children's response to nonsense shapes varying in complexity to the tactual modality. Wooden cut-out shapes varying in number of turns from 3 to 40 were presented to children at Grades I, III, and VI, both for voluntary haptic exploration, and for preference choices. Both of these measures yielded monotonically increasing functions in the oldest group, while the youngest showed a similar but much flatter gradient for exploration times, and an inverted-U shaped preference function; data for the Third Grade subjects were in both cases intermediate. Supplementary data based on an analysis of preference choice latencies for stimulus pairs of adjacent levels of complexity, as well as on ratings of subject's mode of exploration of the stimuli under both response sets showed a marked shift from a predominantly passive to an increasingly active mode of exploration. These results are related to the age differences for the exploration-time and preference data, and discussed in relation to Schachtel's differentiation between allocentric and autocentric modes of perception.     

Carnap's inductive probabilities as a contribution to decision theory

Common probability theories only allow the deduction of probabilities by using previously known or presupposed probabilities. They do not, however, allow the derivation of probabilities from observed data alone. The question thus arises as to how probabilities in the empirical sciences, especially in medicine, may be arrived at. Carnap hoped to be able to answer this question byhis theory of inductive probabilities. In the first four sections of the present paper the above mentioned problem is discussed in general. After a short presentation of Carnap's theory it is then shown that this theory cannot claim validity for arbitrary random processes. It is suggested that the theory be only applied to binomial and multinomial experiments. By application of de Finetti's theorem Carnap's inductive probabilities are interpreted as consecutive probabilities of the Bayesian kind. Through the introduction of a new axiom the decision parameter λ can be determined even if no a priori knowledge is given. Finally, it is demonstrated that the fundamental problem of Wald's decision theory, i.e., the determination of a plausible criterion where no a priori knowledge is available, can be solved for the cases of binomial and multinomial experiments.     

What determines the detection of changes in motion velocity? A comment on Dzhafarov,Sekuler, and Allik (1993)

We comment on a recent model aimed at explaining data on speed of reaction to motion onset and to changes in motion velocity. The model is based on calculating the running variance of the stimulus positions passed during the motion. We show that although the model is successful in explaining data on motion onset and suprathreshold velocity changes, it may not be able to explain data on time of reaction to changes in velocity when these are near the detection threshold.