Jose is attending an outdoor concert and suddenly a loud crack, flying sparks, and a deafening boom fill the arena. Automatically, Jose's heart rate shoots up and a surge of adrenaline incites his desire to flee. The natural or inborn, automatic response to a stimulus or event-such as a spike in heart rate at hearing a loud and unexpected boom-is called a(n) __________.
◦ unconditioned stimulus
◦ conditioned stimulus
◦ unconditioned response
◦ conditioned response