Question

Often motion sickness is relieved when a person looks at far distance objects, such as things located on the far horizon. Why does far distance viewing help in motion sickness while close distance view (like reading a map or book) make it worse?

Answer 1

The nausea or vomiting sensation that is caused by travelling is referred as motion sickness.
Motion sickness is evoked from a mismatch in sensory cues between vestibular, visual, and proprioceptive signals.

If a person views the nearby objects or reads a book, it can produce motion sickness because the accelerations experienced by the vestibular system do not match the visual input.
If a person looks out at the farther distances during the same travel, no sickness occurs because the visual and vestibular cues are in alignment.

Supportive information:

The vestibular system functions to detect head motion and position relative to gravity. This vestibular system is primarily involved in the fine control of visual gaze, posture, orthostasis, spatial orientation, and navigation. Vestibular signals are highly processed in many regions of the brain and are involved in many essential functions.

Motion sickness is vestibular related sensation. Motion sickness is actually one of the side effects of vestibular system's functions, as vestibular signals very much involved in the brain’s information processing that controls such fundamental functions as balance, posture, gaze stabilization, spatial orientation, and navigation etc.

Thus, in many regions of the brain, vestibular information is combined with signals from the other senses as well as with motor information to give rise to motion perception, body awareness, and behavioral control.
The vestibular receptors lie in the inner ear next to the auditory cochlea. They detect rotational motion (head turns), linear motion (translations), and tilts of the head relative to gravity and transduce these motions into neural signals that can be sent to the brain.

The cerebellum forms important regulatory mechanisms for the control of eye movements, head movements, and posture. Many vestibular nuclei neurons have reciprocal connections with the cerebellum.
Damage or disease that interrupts inner ear signal information from one side of the head can change the normal resting activity in the VIIIth nerve afferent fibers and it will be interpreted by the brain as a head rotation, even though the head is stationary. These effects often lead to illusions of spinning or rotating that can be quite upsetting and may produce nausea or vomiting.

The vergence angle is the angle between the lines of sight for each eye. Visual objects that are far away (2 meters or more) require no vergence angle, but as the visual objects get closer (e.g., when holding your finger close to your nose), a large vergence angle is needed. During translational motion, the eyes will change their vergence angle as the visual object moves from close to farther away (or vice versa). These responses are a result of activation of the otolith receptors, with connections to the oculomotor nuclei.
With tilts of the head, the resulting eye movement is termed torsion, and consists of a rotational eye movement around the line of sight that is in the direction opposite to the head tilt. There are major reciprocal connections between the vestibular nuclei and the cerebellum.