Modifications of the Poggendorff effect as a function of random dot textures between the verticals

In the present research, we investigated the modification of the strength of the Poggendortf illusion as a function of different densities ofrandom dot textures failing the space between the verticals. The results ofExperiment 1 show that the illusory effect is a nonlinear function ofthe texture parameterr, the ratio of black pixels to white and black pixels, with a minimum forr=0.5, approximately, and a maximum forr=0 andr=1. The results may be interpreted by an analytical model of perceptual space dynamics, in which the effect dependson the amount of interaction between points of different light intensity. A computer simulation performed by applying the analytical model to different values ofr shows a good agreement between the predictions and the experimental data. To test the hypothesis underlying the model, a second experiment was carried out to measure the magnitude of the expansion ofthe space between the verticals as a function of the parameterr. The results are consistent with the hypothesis of the model. The overall data are discussed in terms of their implications on various theories proposed for the Poggeadorff illusion.     

Do locally defined feature discontinuities capture attention?

Results from previous visual search studies have suggested that abrupt onsets produce involuntary shifts of attention (i.e., attentional capture), but discontinuities in simple features such as color and brightness do not (Jonides & Yantis, 1988). In the present study we tested whether feature discontinuities (i.e., “singletons”) can produce attentional capture in a visual search task if defined “locally” or over a small spatial range. On each trial, a variable number of letters appeared, one of which differed from the others in color or intensity. The location of this singleton was uncorrelated with target location. Local discontinuities were created by embedding the letters in a dot texture. In Experiment 1, display size effects for singleton targets were not reduced with the addition of a background dot texture. Similar results were obtained in Experiment 2, regardless of variations in texture density. Experiment 3 confirmed that when targets are defined by a color or intensity singleton, they are detected preattentively, and that increasing texture density yields faster detection. We conclude that the spatial range over which feature discontinuities are defined may influence the guidance of spatial attention, but it has no influence on their ability to capture attention.     

Explanation and the theory of questions

In The Scientific Image B. C. van Fraassen argues that a theory of explanation ought to take the form of a theory of why-questions, and a theory of this form is what he provides. Van Fraassen's account of explanation is good, as far as it goes. In particular, van Fraassen's theory of why-questions adds considerable illumination to the problem of alternative explanations in psychodynamics. But van Fraassen's theory is incomplete because it ignores those classes of explanations that are answers not to why-questions but to how-questions. In this article I provide a unified theory of explanatory questions that comprehends both how-questions and why-questions, and I show that a question-theoretic approach to explanation can be defended independently of van Fraassen's programme of Constructive Empiricism.     

Intelligence and the Frontal Lobe: The Organization of Goal-Directed Behavior

Basic to the study of individual differences is the concept of “general intelligence” or Spearman'sg.In this article we suggest thatgis largely a reflection of the control functions of the frontal lobe. A series of experiments investigates a phenomenon we callgoal neglect:disregard of a task requirement even though it has been understood and remembered. Subjectively it is as though the neglected requirement “slips the subject's mind.” Previously described in frontal patients, we show that goal neglect can also be seen in some members of the normal population. In line with conventional distinctions between controlled and automatic processing, eliciting conditions for goal neglect include novelty, weak error feedback, and multiple concurrent task requirements. Under these conditions neglect is linked closely togand extremely common after frontal lesions. Following many other models, we suggest that behavior in any task is structured by a set of action constraints or requirements, derived in part from verbal instructions and specified at multiple levels of abstraction. A frontal process of constraint or requirement activation is fundamental to Spearman'sg.     

Eyewitness testimony and memory distortion

Abstract: Do memories change as we acquire new information? Recent research on memory distortion using implicit tests along with research using confidence is reviewed and new studies are presented. Two new studies asked misinformed subjects to provide reasons for their answers. In each study 15% to 27% of subjects said they remembered seeing items they had only read about. In another study subjects were asked to identify the source of misleading items they had seen in slides or read in misleading questions. Subjects were more likely to say they had seen in slides something they read about in the questions than they were to confuse information from two nearly identical sets of slides. Recent work shows that, not only is it possible to distort memory for events, it is possible to implant an entire memory for something that never happened. The evidence is now clear that we can become mentally tricked into making large as well as small changes in the way we recall the past.