**Drowsiness** negatively affects the driver, as it causes an **increase in reaction time** and **difficulty in making decisions** at the wheel. This is because the state of drowsiness generates a feeling of **tiredness and heaviness in the body**, which makes movements slower and clumsier. Additionally, drowsiness can lead to the driver falling asleep for a few seconds without realizing it, increasing the risk of making mistakes.

Drowsiness can be caused by several factors, such as sleeping fewer hours than usual, changing sleep schedules, driving on roads with little traffic, or consuming alcohol and medications before driving. It is also more likely to experience drowsiness when driving at dawn or after eating.

Therefore, under the effects of sleep, it takes longer to make decisions and more mistakes are made, which confirms that **answer 1** is correct.