Visual pursuit biases tactile velocity perception

During a smooth pursuit eye movement of a target stimulus, a briefly flashed stationary background appears to move in the opposite direction as the eye's motion ― an effect known as the Filehne illusion. Similar illusions occur in audition, in the vestibular system, and in touch. Recently, we found that the movement of a surface perceived from tactile slip was biased if this surface was sensed with the hand. This suggests a common process of motion perception between the eye and the hand. In the present study, we further assessed the interplay between these effectors by investigating a novel paradigm that associated an eye pursuit with a tactile motion over the skin of the fingertip. We showed that smooth pursuit eye movements can bias the perceived direction of motion in touch. Similarly to the classical report from the Filehne illusion in vision, a static tactile surface was perceived as moving rightward with a leftward pursuit eye movement, and vice versa. However, this time the direction of surface motion was perceived from touch. The biasing effects of eye pursuit on tactile motion were modulated by the reliability of the tactile and visual estimates, as predicted by a Bayesian model of motion perception. Overall, these results support a modality- and effector-independent process with common representations for motion perception.

Modulation of Velocity Perception by Engine Vibration While Driving

While driving a vehicle, perceiving velocity is important for appropriate operation and is one of the most important factors for preventing collisions and traffic congestion. In contexts where perceiving velocity changes is difficult, such as on an undulating road, the velocity may exceed the speed limit or traffic congestion may occur due to heavy braking to avoid a collision. Hence, we proposed a method of modulating the perception of velocity through tactile stimulation to promote adequate operation for the driver. In contrast to methods using visual and auditory stimulation, this method has advantages of not increasing the visual cognitive load, not disturbing the enjoyment of music, and reliably stimulating the driver. In this study, we constructed a velocity perception model based on vibrotactile stimulation induced by the engine speed and proposed a method of changing the vibrotactile stimulation by altering the shift position of the transmission to modulate the perception of velocity without additional vibration actuators, regardless of the actual velocity. We measured the seat and engine vibration using two different vehicles. The results demonstrated that the peak acceleration frequencies are proportional to engine speed, indicating that the vibration depends upon the engine speed, not the velocity. We implemented a method of changing the shift position in an actual vehicle and verified the feasibility of the method through a psychophysical experiment. The results showed that drivers perceived a higher velocity with increasing engine speed and lower velocity with decreasing engine speed.

Elements of a stochastic 3D prediction engine in larval zebrafish prey capture

The computational principles underlying predictive capabilities in animals are poorly understood. Here, we wondered whether predictive models mediating prey capture could be reduced to a simple set of sensorimotor rules performed by a primitive organism. For this task, we chose the larval zebrafish, a tractable vertebrate that pursues and captures swimming microbes. Using a novel naturalistic 3D setup, we show that the zebrafish combines position and velocity perception to construct a future positional estimate of its prey, indicating an ability to project trajectories forward in time. Importantly, the stochasticity in the fish’s sensorimotor transformations provides a considerable advantage over equivalent noise-free strategies. This surprising result coalesces with recent findings that illustrate the benefits of biological stochasticity to adaptive behavior. In sum, our study reveals that zebrafish are equipped with a recursive prey capture algorithm, built up from simple stochastic rules, that embodies an implicit predictive model of the world.

An Effect of Acceleration on Passively-Changed Arm-Velocity Perception

In recent years, the methods of motor learning using haptic devices that can give motion-related stimuli to learners have been studied. In order to design control systems of the haptic devices that can give learners stimuli so that they can perceive them with proprioception, we need to understand the characteristics of human’s position and velocity sensations. Then, in this study, we examined velocity JNDs (Just Noticeable Differences), in order to understand human velocity-change perception. We, in particular, focused on an effect of acceleration during velocity-change to human velocity-change perception. In the experiment, we enforced subjects to accelerate their hands with a constant acceleration of 1, 8, 16, 32 deg/s2 from before-acceleration velocity of 10 deg/s. Subjects answered whether they perceived velocity-change or not, and we measured velocity JNDs. As a result, it was found that, while the accelerations increased by 32 times, the velocity JNDs decreased by only about 1/2, i.e., from 8.1 to 4.2 deg/s. From this result, it was concluded that the magnitude of acceleration is not a determinative factor for velocity-change perception but a supplementary one.