A stimulus is anything that induces a reaction or change in a specific organ or tissue. Sensitivity, which is the ability of an organism to respond to any stimulus, plays a fundamental role in them .

Stimuli are classified as:

• Internal : changes occur within the body, for example, homeostatic imbalance and blood pressure in our body.
• External : changes occur around us, for example, stimuli originated and perceived by touch and pain.

There are a series of receptors in the body that are responsible for capturing stimuli and processing them, these are:

• • Chemoreceptors detect the presence of chemicals.
  • Thermoreceptors detect changes in temperature.
  • Mechanoreceptors detect mechanical forces.
  • Photoreceptors detect light during vision.
  • More specific examples of sensory receptors are baroreceptors, proprioceptors, hyporeceptors, and osmoreceptors . Which perform innumerable functions in our bodies, such as, for example, mediate vision, hearing, taste and touch.

Examples of Stimuli

1. Hitting the skin with a needle or pin is a good example of encouragement. The sudden withdrawal of the hand is the response to this stimulus.
2. When someone knocks on a door, you jump if you weren’t conscious from the sound. The jump is the response to a stimulus.
3. If you’re holding a hot plate, keep your hand away from it. The encouragement here is to hold the hot plate while the removal of the hand is the response.
4. An example of a stimulus is a shiny object for a baby.
5. An example of a stimulus is a cash inflow into the economy that is designed to help the economy gain momentum or energy.
6. An example of a stimulus used to great effect could be a study whereby eye tracking is used to identify the brand new logo design that customers are most interested in. In this case, the stimulus would be the logo that is presented to the respondents with their response. measured by gaze.
7. Stimuli can also be used in a clinical research setting. For example, after a treatment intervention for acluophobia (fear of the dark), a participant may be exposed to a dark room and their bodily response can be captured at all times. In this case, the darkroom acts as the stimulus.
8. Traffic intersection: Imagine a person driving through an intersection on a green light and being hit sideways by another driver who ran a red light in your direction. A unique experience like this can turn a traffic intersection into a conditioned stimulus for the driver who was hit.

From then on, approaching an intersection, now the neutral stimulus, can cause them to have sweaty palms, grip the steering wheel more tightly, and have an increased heart rate and dilated pupils. The latter are all unconditioned responses that are not learned and occur naturally in response to fear and anxiety.

9. Higher-order or second-order conditioning: The reaction of pets to the sound of a can opener is another classic example of a conditioned stimulus that elicits an unconditioned response. Second-order conditioning can be demonstrated by placing another conditioned stimulus before the sound of the can opener.

Suppose pet food is stored in a cupboard that has developed squeaky hinges. Over time, the animal may begin to associate the squeak with being fed and have the same reaction as if it had heard the can opener. This is second order conditioning.

However, there are limits to this chain reaction. If another neutral stimulus is added, say a bell rings, before the closet door squeaks, the pet is unlikely to begin to associate the bell with feeding, and will have the same brain reaction as with the can opener.