2.1 Perception

Perception is how we make sense of what our senses pick up. It's a mix of bottom-up processing (starting with raw sensory data) and top-down processing (using what we already know to interpret things).

Our perception is shaped by mental shortcuts (schemas), what we expect to see (perceptual sets), and outside factors like context and culture. Gestalt principles explain how we organize visual info, and attention determines what we focus on and process.

Influences on perception

Bottom-up vs top-down processing

Bottom-up processing begins with sensory input from the environment, while top-down processing starts with our existing knowledge and expectations. These two processes work together to create our perceptual experiences.

Key aspects of each type:

• Bottom-up processing:
  • Relies on sensory receptors detecting stimuli
  • Focuses on details and individual elements
  • Processes raw sensory data
• Top-down processing:
  • Draws on prior knowledge and expectations
  • Uses context and memory
  • Helps interpret ambiguous information

Schemas and perceptual sets

Schemas are organized patterns or frameworks of thought that help us categorize and interpret information. They develop through experience and learning, becoming more complex over time.

Perceptual sets influence how we interpret sensory information by creating expectations about what we will perceive. These predispositions can:

• Cause us to see what we expect to see
• Lead to selective attention
• Result in misinterpretation of ambiguous stimuli
• Be influenced by motivation and emotion

External factors in perception

Our environment and experiences significantly shape how we perceive the world. Context plays a crucial role in interpretation, as the same stimulus can be perceived differently depending on its surroundings.

Cultural influences affect perception through:

• Social norms and values
• Cultural expectations
• Communication styles
• Interpretation of symbols and gestures

Personal experiences shape perception by:

• Creating expectations
• Forming biases
• Developing emotional associations
• Building knowledge frameworks

Gestalt principles of perception

The Gestalt approach emphasizes that we perceive whole patterns rather than individual elements. These principles explain how we organize visual information into meaningful patterns.

Key principles include:

• Closure: completing incomplete figures mentally
• Figure-ground: distinguishing objects from their background
• Proximity: grouping nearby elements together
• Similarity: grouping similar elements together

Additional organizational principles:

• Continuity: perceiving continuous patterns
• Common fate: grouping elements that move together
• Good form: organizing elements into simple and regular figures

Attention in perception

Attention acts as a filter that helps us focus on relevant information while ignoring distractions. This process is essential for effective perception and processing of information.

Types of attention include:

• Selective attention: focusing on specific stimuli
• Divided attention: processing multiple inputs
• Sustained attention: maintaining focus over time

Attention limitations can lead to:

• Change blindness (missing big changes in a scene)
• Inattentional blindness (not seeing something obvious because we're focused elsewhere)
• Missed important information
• Reduced processing accuracy

Visual perception processes

Binocular depth cues

Depth perception relies heavily on info from both eyes working together. This binocular vision gives us crucial info about distance and spatial relationships.

The two main binocular cues are:

• Retinal disparity: differences in images between eyes
• Convergence: inward turning of eyes for close objects

Monocular depth cues

Monocular cues allow us to perceive depth using just one eye. These cues are particularly important for creating depth in 2D representations like paintings and photographs.

Primary monocular cues include:

• Relative clarity (distant mountains appearing hazier than nearby trees)
• Relative size (a car looking smaller when far away than when close by)
• Texture gradient (grass appearing more detailed up close but blending together in the distance)
• Linear perspective (railroad tracks appearing to converge as they extend toward the horizon)
• Interposition or objects in front blocking objects behind (a person standing in front of a building partially hiding it from view)

These cues work together to create convincing depth perception, even when viewing flat images or using only one eye.

Visual perceptual constancies

Perceptual constancies help us to maintain stable perceptions despite changing sensory input. This helps us recognize objects and navigate our environment effectively.

Three main types of constancy:

• Size constancy: maintaining perceived size regardless of distance
• Shape constancy: recognizing objects from different angles
• Brightness constancy: accounting for different lighting conditions

Perception of apparent movement

The perception of movement can occur even when viewing static images or discrete stimuli. This phenomenon underlies many forms of visual media and entertainment.

Two key types:

• Stroboscopic movement: created by rapid succession of still images
• Phi phenomenon: illusion of movement between stationary stimuli

These principles are the foundation for:

• Film and animation
• Digital displays
• Electronic signage
• Visual effects