Effects of task-irrelevant texture motion on time-to-contact judgments

We investigated the effect of local texture motion on time-to-contact (TTC) estimation. In Experiment 1, observers estimated the TTC of a looming disk with a spiral texture pattern in a prediction-motion task. Rotation of the spiral texture in a direction causing illusory contraction resulted in a significant TTC overestimation, relative to a condition without texture rotation. This would be consistent with an intrusion of task-irrelevant local upon task-relevant global information. However, illusory expansion did not cause a relative TTC underestimation but rather also a tendency towards overestimation. In Experiment 2, a vertical cylinder moved on the frontoparallel plane. Observers judged its TTC with a finish line. The cylinder was textured with stripes oriented in parallel to its longitudinal axis. It was either not rotating, rotating such that the stripes moved towards the finish line (i.e., in the same direction as the contour), or rotating such that the stripes moved away from the finish line. Both types of texture motion caused TTC overestimation compared to the static condition. Experiment 3 showed that the different effects of task-relevant and task-irrelevant texture motion are not a mere procedural effect of the prediction-motion task. In conclusion, task-irrelevant local motion and global motion are neither averaged in a simple manner nor are they processed independently.     

A perception experiment with time-critical graphics animation on the World-Wide Web

The World-Wide Web offers a potentially interesting tool to collect data from a large and heterogeneous audience. While questionnaires have become rather common on the Internet, its potential reaches far beyond text processing. In principle, it is possible not only to perform interactive, dynamic experiments on the Web, but also to include graphical animation and time-critical responses, such as reaction times. We implemented a visual motion extrapolation task on the Web using the programming language Java, which can be interpreted by standard Web browsers such as Netscape or Internet Explorer. The data collected with this method turned out to be reliable and differed little from data obtained in a controlled laboratory setting, with the exception of conditions with fixation instruction. Thus, the Web can, generally speaking, be used for data collection of large sample sizes. The strengths and weaknesses of dynamic visual simulation experiments on the Internet are discussed.     

Frequency of dream recall by children and their mothers

The present study investigated frequency of dream recall in children and their mothers. Overall, 88 mothers (M age: 38.7 yr., SD=5.0) and their children (45 girls, 43 boys; M age: 9.9 yr., SD= 1.3) participated. A small but significant positive Pearson correlation of .19 between the frequency of dreams reported by mothers and by their children is consistent with Cohen's 1973 hypothesis of a socialization effect on the frequency of dream recall.     

The end is the beginning – the role of residual affective commitment in former interns’ intention to return and word-of-mouth

Interns are ubiquitous in organizations, yet relatively rarely studied, particularly after their temporary organizational membership has ended. Adopting an organizational commitment perspective, we conducted two studies to investigate two important outcomes of former interns’ membership: intention to return to their former employer, and word-of-mouth, that is, promoting the organization as an employer. In Study 1 (N = 436; lagged design), we found that residual affective commitment, that is, the remaining commitment after leaving an organization, related to former interns’ subsequent intention to return and word-of-mouth. In Study 2 (N = 236; cross-sectional design), we replicated our findings, and further found that intention to return was related to (lack of) alternative employment, hiring expectation, and attractiveness of the organization’s location. Location attractiveness also interacted with residual affective commitment on both intention to return and word-of-mouth, albeit in different directions. Overall, our findings suggest that the internship experience relates to future behaviours important for recruiting new (and old) employees. We discuss theoretical and practical implications of our studies.     

Cross-ethnic assessment of body weight and height on the basis of faces

Previous research has revealed a strong relationship between mere visual facial cues and body weight. They can be exploited to validly judge the weight of the human body. We tested to what extent observers are able to judge body weight and height on the basis of same-ethnicity and different-ethnicity faces. Caucasian and Asian observers saw Caucasian and Asian faces and estimated the person’s weight and height – merely on the basis of greyscale photographs of the face. These height and weight estimates were influenced by ethnocentric specifics of familiar face proportion and face–body relationship. Own-ethnicity weight estimations showed higher accuracy than foreign-ethnicity estimations. Observers ignored the changed base-rate for weight of other-culture faces in a culture-egocentric fashion. Height judgments, in contrast, reflect a higher degree of sophistication. A bias toward the own, familiar body proportion was visible here, especially for Japanese observers—however, the height judgments showed that observers were able to incorporate the other-ethnicity height proportion to some extent.     

Who is looking at me? The cone of gaze widens in social phobia

Gaze direction is an important cue that regulates social interactions and facilitates joint attention. Although humans are very accurate in determining gaze directions in general, they have a surprisingly liberal criterion for the presence of mutual gaze. Using an established psychophysical task that required observers to adjust the eyes of a virtual head to the margins of the area of mutual gaze, we examined whether the resulting cone of gaze is altered in people with social phobia. It turned out that during presence of a second virtual person, the gaze cone's width was specifically enlarged in patients with social phobia as compared to healthy controls. The size of this effect was correlated with the severity of social anxiety. As this effect was found for merely virtual lookers, it seems to be a fundamental mechanism rather than a specific effect related to the fear of being observed and evaluated by others.     

Heading backward: Perceived direction of movement in contracting and expanding optical flow fields

Two goals were pursued in an investigation of possible visual sources for directionality judgments of ego-motion. First, J. J. Gibson’s (1950) global radial outflow hypothesis was contrasted with a simple extrapolation strategy. Second, backing-direction judgments capitalizing on the informational equivalence of global radial outflow created during forward ego-motion and global radial inflow during backward ego-motion were explored. In comparing the accuracy of heading and backing judgments, new insights about global flow and extrapolation strategies were found. Consistent with the hypothesis of an extrapolation strategy, Experiment 1 demonstrated that backing judgments were more accurate than heading judgments when linear observer motion was simulated by means of a point-light flow field. In this case, accuracy was higher with two-point-light displays (extrapolation) than with more complex displays (global flow). Experiment 2 showed that in cases where extrapolation was not possible, such as circular motion, no advantage of backing judgments could be found and judgments were generally less accurate. We conclude that, whenever possible, observers use extrapolation to determine their heading/backing. Only when global flow is the only good source of information do they rely on it.     

Time-to-passage judgments on circular trajectories are based on relative optical acceleration

Current theories of arrival time have difficulty explaining performance in the common but neglected case of nonlinear approach. Global tau, a variable supposed to guide time-to-passage (TTP) judgments of objects approaching on linear trajectories, does not apply to circular movement. However, TTP judgments are surprisingly accurate in such cases. We simulated movement through a three-dimensional cloud of point-lights on various circular trajectories. Arrival-time judgments were found to be above chance when observers had to determine which of two expansionless targets would pass them first. Similar to the inside bias observed in heading studies on circular trajectories, observers showed a strong bias to select the target on the inside of their own curved motion path as passing by first. Analysis of the projected target motion revealed that targets on the inside had lower optical velocities and relatively high optical acceleration rates. Empirical TTP judgments agreed best with a strategy based on relative optical velocity changes.     

Differentiating the differential rotation effect

As an observer views a picture from different viewing angles, objects in the picture appear to maintain their orientation relative to the observer. For instance, the eyes of a portrait appear to follow the observer as he or she views the image from different angles. We have explored this rotation effect, often called the Mona Lisa effect. We report three experiments that used portrait photographs to test variations of the Mona Lisa effect. The first experiment introduced picture displacements relative to the observer in directions beyond the horizontal plane. The Mona Lisa effect remained robust for vertical and/or diagonal observer displacements. The experiment also included conditions in which the portrait had averted gaze directions. An interaction between picture position relative to the observer and gaze direction was found. The second experiment followed up on very pronounced individual differences, suggesting that the Mona Lisa effect is even stronger than it should be for half of all observers (over-rotators). These individual differences do not correlate with any of the standard personality dimensions (Big Five) or with spatial intelligence. In the third experiment, we extended the experiment to virtual 3D heads using the same gaze directions and picture displacements as for the 2D portrait faces. Besides the picture displacements relative to the observer, we also added observer displacements relative to the picture. 3D pictures showed the Mona Lisa effect, but to a smaller extent than did 2D pictures.