The infant does not need to grasp tightly or walk in the first few months after birth -- instead, it needs to feed and develop. Only when those basic functions are complete does the brain kick in for further development (Kalat, pp 124-5). Part 3 - Haloperidol is a drug that blocks dopamine synapses. What effect would it be likely to have in someone suffering from Parkinson's disease?

Dopamine is an organic chemical that is a neurotransmitter and hormone. It is responsible for a number of neurological functions: reward-driven learning, motor function, voluntary movement, cognition, and mood. Parkinson's disease is an age-related degenerative condition that causes tremors, motor impairment, and lack of the individual's ability to control which muscles react to stimuli. Scientists believe that Parkinson's is caused by the loss of dopamine-secreting neurons in a part of the brain called the substantia nigra. This is an area of the midbrain that plays an important role in...

If a Parkinson's patient already has a loss of dopamine, then the use of haloperidol would have a negative effect, likely increasing the symptoms of the disease (Kalat, p. 261).
Part 4 - Neurologists assert that if people lived long enough, sooner or later everyone would develop Parkinson's disease. Why?

Many researchers believe that Parkinson's is a genetic disorder that occurs in 20 times more of the population than is diagnosed. They believe it is both age and environmentally related, and that a combination of environment stress, the body's inability to repair cells as one ages, means that eventually, this gene would be expressed more if people lived longer. It would simply be a matter of statistics: the older the patient, the more likelihood of environmental damage and the less ability to repair cellular mechanisms (Kalat, p. 249, 256).

Source:

Kalat, J. (2010). Biological Psychology, 11th ed.…