Sensory Processing and Perception

Definition of Senses: Our senses include vision, hearing, smell, taste, and body (skin) sensations.
Nature of Stimuli for Each Sense:
- Vision: Stimulus is waves of electromagnetic radiation.
- Body Sensations (Skin, Muscles, Organs): Triggers specific receptor types embedded in tissues that detect sensations such as pain or pressure.
- Sound: Compression waves traveling through a medium, most commonly air. Sound can also be processed through other mediums, such as water (e.g., underwater in a swimming pool, though it may be distorted).
- Smell: Triggered by volatile chemicals present in the air.
- Taste: Triggered by chemicals present in the mouth.

Limited Information Processing: Humans only process a limited amount of the information available in the world.
Species-Specific Processing: Other species possess sensory capabilities beyond human limits:
- They can hear ranges of sound frequencies that humans cannot.
- They can see ranges of electromagnetic radiation that humans cannot.
- They can detect odors that humans cannot.
Reason for Limitation: This selective processing prevents the sensory system from becoming completely overwhelmed. If the brain attempted to process all available information, it would be unmanageable.
Dampening Mechanisms: The sensory system not only dampens the signal from the outset, processing only a subset of what's present, but also employs additional mechanisms further up the processing pathway to filter information.

Concept: The just noticeable difference refers to the minimum amount of change required for a person to detect that two stimuli are, in fact, different.
Factors Affecting JND:
- Range of Processing: The ability to detect a difference is dependent on whether the stimuli fall within the individual's sensory processing range (e.g., one must be able to see wavelengths to differentiate them).
- Energy Level: JND is affected by the energy level of the stimulus. It's often easier to detect a difference between two stimuli that are very high in energy compared to very low-energy stimuli. For example, it's harder to differentiate between two very dim light sources than between two brighter ones that differ by the same absolute amount of energy.

Definition: The idea that an individual may perceive things without being consciously aware that they have processed that information.
Possibility: Yes, it is possible to perceive things subliminally.
Historical Example (Vance Packard/James Vicary):
- Claim: In the late 1950s, it was claimed that flashing messages like "Drink Coca-Cola" or "Eat Popcorn" for a single frame during movies could subliminally influence audience behavior.
- Methodology: These messages were inserted so briefly (e.g., 1 frame) that viewers could not consciously report seeing them.
- Reported Outcome: It was claimed that these subliminal messages increased the sales of the advertised items.
- Reality: In actual films, approximately 12 frames are typically needed for an image to be consciously perceivable. Therefore, single-frame insertions would likely only create an unspecific awareness of 'something' without conscious recognition.
Modern Example (Priming Tasks):
- Procedure: A word (e.g., "chair") is flashed to a participant too quickly for conscious processing. The participant might report not being sure what they saw.
- Effect: Later, when given a fill-in-the-blank task with the first few letters (e.g., "CH_ _ _"), the participant is more likely to complete it with the previously flashed word ("chair") due to the subliminal prime.

Nature of Stimulus: Waves of electromagnetic radiation.
Visible Light Spectrum (Human Perception):
- Slide Indication: Approximately 400 to 700 nanometers in wavelength.
- Accurate Range: More precisely, the human eye processes wavelengths from about 380 to 760 nanometers.
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