Sensation and Perception Overview

Sensation and Perception Overview

• Sensation is the detection of physical energy emitted or reflected by objects. External energy stimulates receptors in sense organs
• Perception is the process by which individuals organize and interpret sensory information to give meaning to their environment.
• Perceptions differ from person to person. Each individual perceives the same situation differently
• Group perceptions can influence an individual's perception
• Past experiences and important values influence how individuals organize and interpret sensory information.

Psychophysics

• Psychophysics is the branch of psychology that studies the effects of physical stimuli on sensory perceptions and mental states.
• Gustav Fechner (1801-1887) is credited with founding the scientific study of psychophysics. Their research focused on studying the relationship between the strength of stimuli and a person's ability to detect the stimulus.
• Absolute threshold of sensation is the smallest amount of a stimulus that can be detected.
• The difference threshold (JND) is the smallest change in a stimulus that can be detected. Weber's Law is relevant here- the JND depends not on the size of change, but rather the proportion of the initial stimulus.

Absolute Thresholds

• The human eye can detect the equivalent of a single candle flame burning 30 miles away and can distinguish among over 300,000 different colors.
• The ear can detect sounds as low as 20 hertz and as high as 20,000 hertz. A quiet room's clock ticking 20 feet away can be heard also.
• The sense of taste can detect a teaspoon of sugar dissolved in 2 gallons of water
• Perfumes can be detected at quantities of one drop in a 3 room apartment
• The touch can feel the wing of a bee dropped from 1 centimeter

Transduction and Coding

• Transduction is the conversion of stimuli detected by receptor cells into electrical impulses that travel to the brain.
• Coding occurs when the brain transforms these electrical impulses into specific sensations.

Perception Summarized

• Stimuli such as light or sound travel to sensory receptors
• Then signal travels along neural pathways to the brain
• Based on the stimuli the brain makes sense of the stimuli leading to sensation and eventually perception.
• Both sensation and perception are needed to give meaning to the environment.

Perception: Distal and Proximal Stimuli

• Distal stimulus: external object sensed
• Proximal stimulus: representation of the distal stimulus on the sensory apparatus. (e.g., on the retina)

Functions of Perception

• Five major functions that a perceptual system performs include:
  • Attention: determining which part of the sensory environment to attend to
  • Localization: determining the location of objects
  • Recognition: determining what the object is
  • Abstracting: taking critical information from the objects
  • Perceptual Constancy: maintaining a constant appearance or perception of objects despite changes in retinal images of the objects.

1. Attention

• Focused attention is a part of the perceptual experience that aids in distinguishing an object from the surroundings, keeping us alert, and focusing on task-relevant information
• Attention is a part of perceiving the environment, allowing a person to selectively focus on information and select relevant information

2. Localization

• Localizing objects involves determining their position in the up-down and left-right dimensions
• Depth perception (e.g., distance cues) and direction in which an object moves
• Locating things requires knowing how far away they are

Perceptual Grouping

• Gestalt's laws of grouping describe how parts of a scene group pre-attentively according to certain laws and principles. Factors to consider for grouping include:
• Continuity: elements that appear to form a smooth continuation are perceived as a single unit
• Proximity: elements that are close together tend to be perceived as a group
• Similarity: elements that are similar tend to be perceived as a group
• Closure: elements are perceived as a closed unit despite the interruptions

3. Recognition

• Recognition involves correctly establishing the various features of an object.
• Example: knowing an object is a loaf of bread rather than a mailbox
• Perception is pre-processed to a point where features are recognized based on context.

4. Abstraction

• Abstraction is the process of converting sensory information (like lines and shapes) into abstract categories.
• Example: converting raw sensory information to recognized forms like letters, words, or objects.
• It requires less storage space than raw information.

5. Perceptual Constancy

• Perceptual constancy allows us to perceive objects (e.g., their color, size, and shape) as remaining largely constant across variations in sensory conditions.
• Various factors like color, brightness, and size influence perception.

Explore the concepts of sensation and perception in psychology. This quiz covers the definitions, influences on perception, and the basics of psychophysics introduced by Gustav Fechner. Understand how sensory information is processed and interpreted to create individual experiences.