Persons may or may not express their sexual orientation in their behaviors. In most people, sexual orientation is shaped at an early age. There is also considerable recent evidence to suggest that biology, including genetic or inborn hormonal factors, play a significant role in a person's sexuality. In summary, it is important to recognize that there are probably many reasons for a person's sexual orientation and the reasons may be different for different people. No, human beings can not choose to be either gay or straight.
Sexual orientation emerges for most people in early adolescence without any prior sexual experience.
Although we can choose whether to act on our feelings, psychologists do not consider sexual orientation to be a conscious choice that can be voluntarily changed. Even though most homosexuals live successful, happy lives, some homosexual or bisexual people may seek to change their sexual orientation through therapy, sometimes pressured by the influence of family members or religious groups to try and do so. The reality is that homosexuality is not an illness. It does not require treatment and is not changeable. However, not all gay, lesbian, and bisexual people who seek assistance from a mental health professional want to change their sexual orientation.