Final answer:
Warning signals are not always required for the perception of a stimulus. Our perception can be influenced by motivation, with concepts like signal detection theory and sensory adaptation showing that humans can perceive stimuli without explicit warnings. Habituation and innate responses to environmental changes further demonstrate our ability to detect and respond to stimuli without being warned.
Step-by-step explanation:
We do not always need a "warning" signal to warn us of a stimulus. This is evident in concepts such as signal detection theory, where motivation can influence our perception of stimuli amidst background noise. For instance, the anticipation of a crucial phone call can make us think we hear the phone, even when no call is taking place. Similarly, a mother might wake up to her baby's soft sounds, but not to other background noises.
Sensory adaptation is another reason we do not necessarily need a warning signal. When exposed to a continuous stimulus, like a flashing light, we eventually stop perceiving it even though the sensation is still being sensed by our eyes. Furthermore, subliminal messages are stimuli presented below the threshold of conscious awareness, indicating that we do not always need to be warned to perceive or respond to stimuli.
Moreover, animals and humans demonstrate behaviors like habituation, where organisms learn to ignore stimuli that are not harmful, circumventing the need for a warning.
Lastly, our sensory systems are primed to assist us in detecting and interacting with our environment, often without explicit warnings. Many animals are equipped with innate abilities to detect changes in the environment, such as earthquake tremblings, which enable them to react without the need for a traditional warning signal.