In basic psychology and sensory physiology, the process in which receptors in our sense organs are first activated or triggered directly by external stimuli is called what?

Introduction / Context:
Human experience of the world begins with our senses. Light, sound, pressure, chemicals, and other forms of energy reach specialised receptors in our eyes, ears, skin, nose, and tongue. The first step in this chain is simply detecting the presence of a stimulus. Psychology textbooks distinguish between sensation, the initial detection, and perception, the later interpretation and conscious awareness. This question asks which term best describes the activation of receptors by stimuli.

Given Data / Assumptions:
- Receptors in sense organs respond to external physical or chemical stimuli.
- The question focuses on the initial activation step, not later stages like interpretation.
- Options include perception, habituation, adaptation, and sensation.
- We assume standard introductory psychology definitions of these terms.

Concept / Approach:
Sensation refers to the process by which sensory receptors and the nervous system receive and represent stimulus energies from the environment. When light strikes photoreceptors in the retina or sound waves move hair cells in the inner ear, these receptors convert physical energy into neural signals. Perception is the process of organising and interpreting those sensory signals to recognise objects, sounds, and events. Habituation is a psychological process in which response to a repeated non threatening stimulus decreases over time. Adaptation may refer to sensory adaptation, where receptor sensitivity changes after continuous stimulation (for example, getting used to a smell). The question asks specifically about activation or triggering of receptors by stimuli, which matches the definition of sensation, not perception or the other processes.

Step-by-Step Solution:
Step 1: Identify the key phrase in the question: activation of receptors by stimuli. Step 2: Recall that sensation is defined as the detection of physical energy by sense organs and the transmission of this information to the brain. Step 3: Recognise that perception involves interpreting the sensory information, which happens after receptors have already been activated. Step 4: Note that habituation is about decreasing response to repeated stimuli, not initial activation. Step 5: Remember that sensory adaptation describes changes in sensitivity with continuous stimulation, again not the first moment of activation, and select sensation as the correct term.

Verification / Alternative check:
Introductory psychology books often present a simple chain: stimulus → sensation → perception. They give examples such as light waves becoming neural impulses in the retina (sensation) and then being organised to recognise a face (perception). Separate sections describe habituation and adaptation as different phenomena that modify responses over time. Definitions and examples clearly show that sensation is the specific word used when talking about receptors being activated by stimuli and starting neural transmission.

Why Other Options Are Wrong:
- Perception, the interpretation and meaning given to sensory input, occurs after the receptors have already been activated and signals have reached brain areas.
- Habituation, a decrease in response after repeated exposure, describes how reactions change with repetition, not the basic detection process.
- Adaptation, a change in sensitivity after continuous stimulation, modifies how receptors respond over time but is not the same as the initial activation by a new stimulus.

Common Pitfalls:
Students sometimes use sensation and perception as if they mean the same thing, but in psychology they refer to different stages. Others may confuse adaptation or habituation with initial sensing because all involve changes in response to stimuli. A helpful way to remember is that sensation is the raw data coming from the senses, while perception is the meaning given to that data. When a question mentions activation of receptors by stimuli, think of the first step—sensation—which starts the whole process of experiencing the world.

Final Answer:
The activation of receptors by stimuli is called Sensation, the initial detection of energy by sensory receptors.