Which of the following is a common effect of nicotine?

Increased attention and concentration is a common effect of nicotine, primarily due to its stimulant properties. When nicotine enters the body, it stimulates the release of neurotransmitters like dopamine and norepinephrine, which enhance alertness and cognitive functioning. This stimulation can lead to improved focus and a heightened ability to concentrate on tasks.

Nicotine acts on the central nervous system and can create a feeling of increased mental clarity. This is particularly relevant in contexts where individuals might seek to stay alert or improve task performance. The acute effects of nicotine can lead to temporary enhancements in attention span, which is why it is commonly associated with greater cognitive engagement during use.

In contrast, heightened relaxation, substantial sedation, and deep sleep are not typical effects of nicotine. In fact, nicotine's stimulant effects are generally opposite to these states, making the choice of increased attention and concentration the most fitting answer for this question.