Fig 1.
The experimental condition for speed perception tasks.
Visual stimuli were moved from far to near and eye movements during the task were measured.
Fig 2.
A two-alternative forced-choice paradigm.
World constant task (A): the green circle (visual target) moved from far to near at constant velocity in the real world, while participants kept their eyes on the red circle (fixation point). Retinal constant task (B): visual target moved from far to near at constant velocity on the retina, while participants kept their eyes on the fixation point. In both speed perception tasks, participants compared the target speed between the standard and comparison stimuli.
Fig 3.
Target velocity of a speed perception task in the real world and on the retina.
In the world constant task, the far (A), middle (B) and near (C) conditions are shown, and the target moves at a constant speed in the real world (physically), but it moves with acceleration on the retina. In the retinal constant task, the far (D), middle (E). and near (F) conditions are shown, and the target moves at a constant speed on the retina, but it moves with deceleration in the real world. The dotted, dashed-dotted, solid, short dashed and long dashed lines represent the order of speed. The blue, black and red lines indicate the far, middle and near conditions, respectively. The black solid lines indicate standard stimuli.
Fig 4.
A typical example of psychometric functions for the world constant task.
Colors indicate the three different initial positions of the target from the participants: blue, black and red lines are the far, middle and near conditions, respectively.
Fig 5.
The comparison of the PSE between the far, middle and near conditions in the world constant task.
Error bars indicate the standard deviation. *: p < 0.05.
Fig 6.
The comparison of the probabilities between the far, middle and near conditions in the retinal constant task.
Colors indicate the three different initial positions of the target from the participants: blue, black and red bars are the far, middle and near conditions, respectively. Error bars indicate the standard deviation. *: p < 0.05.
Fig 7.
A two-alternative forced-choice paradigm.
Fixation task (A): a green circle (visual target) moved from far to near at constant velocity in the real world and participants kept their eyes on the red circle (fixation point) in both standard and comparison stimuli. Eye movements task (B): a visual target moved from far to near at constant velocity in the real world, and participants kept their eyes on the fixation point in the standard stimulus and pursued the target with their eyes in the comparison stimulus. For both speed perception tasks, the participants compared the target speed between the standard and comparison stimuli.
Fig 8.
Typical examples of psychometric functions for the eye movements tasks.
The blue, black and red lines indicate the far, middle and near conditions, respectively.
Fig 9.
Comparisons of psychometric functions between the fixation and eye movements tasks in the far (A), middle (B) and near (C) conditions. The light colored and dark colored lines indicate the fixation and eye movement tasks, respectively. The blue, black and red lines indicate the far, middle and near conditions, respectively.
Fig 10.
The comparison of the PSE between the far, middle and near conditions in the fixation and eye movements tasks.
Error bars indicate the standard deviation. *: p < 0.05.
Fig 11.
Typical examples of the velocity of convergence eye movements at target velocity of 25.0 cm/s for the eye movement task in the far (A), middle (B) and near (C) conditions. The thin and thick lines indicate the velocity for each trial and the mean velocity, respectively. The dotted lines indicate target velocity.
Table 1.
Mean values (± SD) of the mean velocity of convergence eye movements from 100 to 400 ms after the motion onset at each target velocity in three different conditions.