On “knowing your partner”: Dangerous illusions in the age of AIDS?

We identified two characteristics of the impression formation process that may cause people to underestimate the riskiness of potential sexual partners. In Study 1, participants were quite confident that they could determine whether someone was lying to them about risk-related behavior when, in reality, they could not. Particularly troubling was a “truth bias” that resulted in relatively high rates of truth detection, but poor lie detection. In Study 2, increased familiarity with a target person (who actually was HIV+) caused participants to lower their estimates of the target's riskiness, despite the fact that we explicitly warned them that the target might be HIV+. We suggest that such processes may foster the illusion of knowing one's partner when one does not.     

Suffering, sovereignty, and the purposes of God: Christian convictions and medical killing.

Despite a variety of "non-ecumenical" features in Christian arguments about suicide, assisted suicide, and euthanasia, there are obvious "ecumenical" aspects to be found in the general Christian prohibition of these practices. A fair reading of the Christian tradition requires that we acknowledge both the differences that distinguish particular perspectives and the fundamental themes that allow an identifiably Christian position to emerge in stark contrast to the secular discussion of these issues. Central to Christian interpretations of dying and death are an acknowledgment of God's sovereignty over human life, an understanding of suffering that stresses identification with Christ as the source of Christian hope, and the recognition that God's creative and redemptive purposes are generally (or always) at odds with the deliberate choice of assisted suicide or euthanasia.     

Active control in interrupted dynamic spatial orientation: The detection of orientation change

Gibson (1966, 1979) suggested that an important property of perception is that the observer is active. Two experiments were conducted to examine the benefits of active observation in determining dynamic spatial orientation. Subjects were presented with displays simulating locomotion through a three-dimensional environment. Active observers continuously controlled locomotion, whereas passive observers viewed the display. During the trial, the display was blacked out for a brief period, followed by a static image that was at either the correct or the incorrect orientation following the blackout. Subjects were required to indicate whether they were positioned at the correct extrapolated orientation. The presence or absence of orientation change, the type of change (changes in rotation about the depth axis [roll], horizontal axis [pitch], or forward translation), the duration of the blackout, and the consistency of change were varied. In addition, the experiments used either a compensatory or a pursuit tracking task. Active observers had greater sensitivity than did passive observers in detecting a change for both tracking tasks. Subjects in both experiments exhibited greater sensitivity in detecting inconsistent changes (relative to consistent changes), suggesting that the dynamics specified by optical flow were incorporated in extrapolated orientation. In addition, sensitivity decreased with an increase in blackout duration. The results are discussed in terms of an extrapolation model of perception that incorporates the responses executed by active observers.     

Target and nontarget grouping in visual search

Results recently reported by Driver, McLeod, and Dienes (1992) are used to contrast three accounts of visual search—in particular, their mechanism for easy conjunction search. In the Driver et al. study, the target was defined by a conjunction of form and movement; the key manipulation was phase in both target and nontarget motion sets. Mechanisms working separately on each display element (inhibition from nontarget features, facilitation from target features) are unable to explain large effects of phase, since this is defined only by relationships between one element and another. As implemented in the guided search model of Cave and Wolfe (1990), local suppression between similar elements is also unable to account for the results. More promising is an approach based on perceptual grouping: Elements moving in phase can be selected (target motion) or rejected (nontarget motion) as a group. Rather than a bias against elements that are similar to or grouped with their neighbors, there is a bias to treat grouped elements together.     

A pointing technique for rapidly collecting localization responses in auditory research

A technique is described for rapidly collecting responses in auditory-localization experiments. Subjects indicate the perceived direction of the sound by pointing at a 20-cm-diam spherical model. In Experiment 1, the subjects judged the direction of a broadband signal, which could originate from any of 239 directions ranging through 360° of azimuth and between ?45° and +90° of elevation. Using this technique, the subjects responded 2–8 times more rapidly than previous subjects who used either a verbal-reporting technique or a head-pointing technique. Localization judgments were as accurate as they had been with verbal reports, but were not as accurate as judgments collected using the head-pointing technique. In Experiment 2, the signal was turned off and the experimenter read the spherical coordinates of the signal location to the subjects. The subjects pointed to these coordinates more accurately than they had judged the direction of the sounds in Experiment 1, suggesting that the response technique had not been the limiting factor in that experiment. Circumstances relevant to the choice of response techniques for auditory-localization experiments are discussed.     

Use of a computer-controlled firearms training simulator in perception response time experiments

This paper describes the use of a custom-configured computer-controlled firearms training simulator to measure perception response (reaction) time (RT) to a stimulus in which the degree of threat presented is a manipulable variable across trials. The computer records the number of frames of videotape traversed between the point of presentation of the threat in the video stimulus and the point at which the subject responds by drawing the firearm. For the purposes of data analysis, these frame-count measures are converted to RT measurements. Example data are presented that capture perception RT at both thedraw-stimulus and thefire-stimulus points in situations for which either only one threat or more than one threat exists. Other elements, such as degree of threat and accuracy of response, provide additional data.     

Computer games: Paradigms of opportunity

Computer games offer unique opportunities to apply unobtrusive constraints to action that permit meaningful analysis without destroying the integrity of the game itself. To a much greater extent than most traditional laboratory tasks, computer games represent holistic, meaningful, and natural human activity. Considerable concern about the appropriate analysis and interpretation of results, however, remains. One strategy that addresses these concerns involves the adoption of separate but convergent analytic perspectives. This article suggests that three such perspectives (viz., the objective, the subjective, and the empirical) can be combined to provide the necessary logical leverage to allow meaningful research. Alternative analyses of data collected from the playing of a particular arcade-type computer game are used to illustrate this point.     

IDAC computer interfacing for an undergraduate learning laboratory

A hardware and software interface system from International Data and Acquisition and Control, Inc. (IDAC) is reviewed. The IDAC system comes with spreadsheet software compatible for either Macintosh or IBM microcomputers. I prefer to use the IDAC hardware with my own software written in TrueBasic and spreadsheet macros. The entire system is easy to use and is currently in use for our undergraduate Learning Laboratory.     

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.