Current theory proposes that baseball outfielders catch fly balls by selecting a running path to achieve optical acceleration cancellation of the ball. Yet people appear to lack the ability to discriminate accelerations accurately. This study supports the idea that outfielders convert the temporal problem to a spatial one by selecting a running path that maintains a linear optical trajectory (LOT) for the ball. The LOT model is a strategy of maintaining "control" over the relative direction of optical ball movement in a manner that is similar to simple predator tracking behavior.

We tested a finding by E. S. Robinson (1933) that people have a bias to turn right upon entering a building. We hypothesized that this bias is attributable to learning derived from traffic rules that specify driving on the right side of the road and that it also could be related to handedness. We tested participants in both the United States and England in a simple "T-maze" task in order to compare their directional preference. Handedness was the best predictor of participants' directional preference. However, U.S. participants also were statistically more likely to turn right than were English participants. The preference to turn right was not found to be significantly related to eye dominance or reading direction of the primary written language of the participant, although in the case of reading direction, the sample size of right-to-left readers was too small to be conclusive. The findings support that walking direction preference is an additive function of both learned driving patterns and genetic handedness. These findings have practical implications for the design of public spaces such as schools, businesses, and urban centers.

Using micro-video cameras attached to the heads of 2 dogs, we examined their optical behavior while catching Frisbees. Our findings reveal that dogs use the same viewer-based navigational heuristics previously found with baseball players (i.e., maintaining the target along a linear optical trajectory, LOT, with optical speed constancy). On trials in which the Frisbee dramatically changed direction, the dog maintained an LOT with speed constancy until it apparently could no longer do so and then simply established a new LOT and optical speed until interception. This work demonstrates the use of simple control mechanisms that utilize invariant geometric properties to accomplish interceptive tasks. It confirms a common interception strategy that extends both across species and to complex target trajectories.

The authors investigated whether behavior of fielders pursuing uncatchable fly balls supported either (a) maintenance of a linear optical trajectory (LOT) with monotonic increases in optical ball height or (b) maintenance of optical acceleration cancellation (OAC) with simultaneous lateral alignment with the ball. Past work supports usage of both LOT and OAC strategies in the pursuit of catchable balls headed to the side. When balls are uncatchable, fielders must choose either optical linearity or alignment at the expense of the other. Fielders maintained the LOT strategy more often and for a longer period of time than they did the OAC alignment strategy. Findings support the LOT strategy as primary when pursuing balls headed to the side, whether catchable or not.

Four studies illustrate a new auditory illusion associated with the Doppler effect and demonstrate a new influence of dynamic intensity change on perceived pitch. Experiment 1 confirmed the existence of a popular belief that the pitch of a moving sound source rises as the source approaches. Because there is no corresponding rise in frequency, the authors refer to the perceived pitch rise as the Doppler illusion. Experiment 2 confirmed that the effect occurs perceptually, so the belief in a "naive principle" of physics has a perceptual basis. Experiment 3 confirmed the effect does not occur under matched static conditions. Experiment 4 showed that the influence of dynamic intensity change on perceived pitch occurs outside the realm of Doppler stimuli. The findings support a dynamic dimensional interaction of pitch and loudness, with marked differences in the perception of pitch and loudness under static and dynamic conditions. For 2 days in 1845 a locomotive pulled an open car of trumpeters past a group of observers to demonstrate a new principle of wave mechanics derived by Johan C. Doppler (Doppler, 1842). The Doppler effect, as it came to be known, refers to the change in frequency that occurs when there is relative motion between a wave-emitting source and an observer. Familiar examples may be the pitch change heard in a train's horn as it passes a crossing or an ambulance siren as it passes on the street. The Doppler effect has since become a valuable tool in various fields that use wave mechanics, including astronomy, communications, meteorology, and medicine. Applications range from tracking the movement of galaxies to monitoring fetal heart activity.In the auditory domain a sound source traveling at a constant velocity past a stationary observer will drop in observed frequency both as it approaches and departs. Here, the term observed frequency refers to the physical frequency of the sound, measured at the point of observation. The present work introduces and investigates a perceived rise in pitch for a passing sound source as it approaches an observer. Because no rise in frequency actually occurs, we call this perception the Doppler illusion. In addition, we begin to explore how these findings may relate to auditory localization, current models of pitch perception, and how the dy-

Three experiments showed that dynamic frequency change influenced loudness. Listeners heard tones that had concurrent frequency and intensity change and tracked loudness while ignoring pitch. Dynamic frequency change significantly influenced loudness. A control experiment showed that the effect depended on dynamic change and was opposite that predicted by static equal loudness contours. In a 3rd experiment, listeners heard white noise intensity change in one ear and harmonic frequency change in the other and tracked the loudness of the noise while ignoring the harmonic tone. Findings suggest that the dynamic interaction of pitch and loudness occurs centrally in the auditory system; is an analytic process; has evolved to take advantage of naturally occurring covariation of frequency and intensity; and reflects a shortcoming of traditional static models of loudness perception in a dynamic natural setting.

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When an occlitded horizontal row of shapes is shifred laterally, apparenr motion can be experienced in either the lefrward or the rightward direction. Foitr experiments provide evidence for a motion bias in the direction that shapes appear to face. The bias tended to be largest when directionality was specified geometrically (e.g.. triangles), next largest when it was specified biologically (e.g., mice). and absent when it was speciBed calligraphically (e.g., letter R). The bias increased parametrically as a fiinction of triangle pointedness and was consistent with th< directional interpretation of an ambigiioirs diick-rabbit. The results support the existence of a cognit ively specified fonvard-facing attribute that can injlrtence experienced direction of motion.