Selective Attention & Limits: Psychology

• Selective attention reduces sensory information by focusing on specific sensory input
• Brain structures select and divert incoming sensory messages during selective attention, narrowing the information channel that links senses to perception

Limits of Attention: Multitasking

• Dividing attention results in poor consequences because it is not possible to do multiple things at one time when they require focus
• When dividing attention to complete multiple things at once, you are likely task-switching
• Task-switching is moving attention rapidly between each thing you're working on
• Task-switching does not work well when tasks demand significant attentional resources
• Well-practiced tasks can be carried out with more attention-demanding tasks with some success, making it seem like multi-tasking

Influencing Selective Attention

• Attentional resources are limited and need allocation

How to Select What We Attend To

• Intense stimuli such as brighter, louder, larger, or sharper command attention
• Attention relates to contrast or change in stimulation like bold, italics, capitals, and lowercase, because they change from the usual pattern and are unexpected
• Humans divert attention toward things that are important, called "Cocktail Party Effect"

Goals and Attention

• Attention is purposefully directed to meet goals
• Inattentional blindness: Failure to notice a stimulus because attention is focused elsewhere
• Change blindness: Failure to notice that the background in the field of vision is changing, because focused on one specific element of the scene
• Blindness occurs when attention is narrowly focused to address a goal
• People miss things that are not expected

Attention in Everyday Life: Mind-Wandering

• Mind-wandering is the tendency for attention to stray to internal things unrelated to stimuli in the environment
• Mind-wandering is beneficial and associated with increased creativity and relief from boredom
• Mind-wandering allows planning and goal setting because it is future-oriented
• Sometimes mind-wandering is intentional and may arise when people believe the task requires full attention

Perception

• Perception is when the brain organizes and interprets impressions into meaningful patterns
• "Seeing" and "hearing" take place in the brain, not in the eyes or ears
• Perceptual misconstruction leads to illusions
• Illusion: Information sent to the brain from the senses that is interpreted inconsistently with objective reality
• Illusions are distorted perceptions of stimuli that exist
• Hallucination: Perceiving objects or events that have no external reality
• Synesthesia: Perceptual constructions or mental models of external that are actively created by the brain
• Synesthesia reveals how powerfully the brain seeks meaningful patterns in sensory input to make perceptual experience

Processes That Underlie Perceptual Construction

• Perceptions are constructed in both a bottom-up and top-down fashion
• Bottom-up Processing: Constructing at the "bottom" with raw materials by using sensory impressions, and putting them together to build a complete perception
• Top-down Processing: Uses prior knowledge and experience that provides an "overall building plan" for a rapid guide for the perception of meaningful wholes without distinctly processing the individual components

Applying Perceptual Construction

• Faces are perceived holistically as a complete unit
• Past experience guide perception of a face, providing instant information about familiarity

Figure-Ground Organization

• The simplest organization involves grouping some sensations into an object, or figure, that stands out against a plainer background (Gestalt Psychology)
• Top-down perceptual processes are apparent for ambiguous stimuli (patterns allowing more than one interpretation)

Actively Constructing Meaningful Perceptions

• Meaningful perceptions are actively constructed using past experience as a guide

Similarities and Differences in People's Perception

• Similarities and differences in perception stem from sensory organs and past experiences

Perceptual Similarities Due to Transduction

• Common perceptual experiences result from normally functioning sensory organs transducing information the same way

Perceptual Similarities Due to Experience

• Many perceptual experiences are the same because of perceptual constancies or the "rules of thumb" the brain develops based on years of experience interpreting the world Shape Constancy: The shape of an object remains stable, even though the shape of its retinal image changes Size Constancy: The perceived size of an object remains the same, even though the size of its image on the retina changes Brightness Constancy: The brain have learned that the relative brightness of objects stays the same even as lighting conditions change

Perceptual Differences Due to Transduction

• Same sensory experience can result in very different perceptions and stem from differences in the sensory impressions that come transducers
• Differences can happen due flaws in the genetic code for the sense organs (ex., color blindness or weakness)
• Differences can also happen due to environmental trauma (ex., Childhood abuse or repeated exposure to very loud music)
• Differences can also happen due to age for compromise their ability to transduce environment stimuli

Perceptual Differences Due to Experience

• Past experience can also shape differences in perception, since brains are different and interpret what’s seen as if it's the default setting that's present

Diversity and Perceptual Differences

• Müller-Lyer illusion has horizontal lines with arrowheads that appear shorter than lines
• Richard Gregory believes that we see the line with the arrowheads as if it were the nearby corner of a room, joining two walls receding from it
• Size-distance invariance: If two objects make images of the same size, the more distant object must be larger
• Perceptual habits misperceive the Müller-Lyer lines we acquire while living in a "carpentered world"

Depth Perception

• Depth perception is the ability to see space and to accurately judge distances for a 3-D experience of the world around us
• Depth perception begins to develop as early as within two weeks of age and continues to improve up until six months of age

Depth Perception and the World of Art

• Depth cues are features of the environment and messages from the body to supply information about distance and space
• Our visual system uses two cues: binocular and monocular

Binocular Depth Cues

• Require two eyes and is based on the fact that the eyes are about 2.5 inches apart and project slightly different images of the world to the retina, called retinal disparity
• When the images fuse into an overall image, stereoscopic vision (3-D sight) occurs results
• Convergence: The degree to which the eyes turn in to focus on a close object
• Muscles attached to the eyeball feed information on eye position to the brain to judge distance

Monocular Depth Cues

• Can be perceived with just one eye
• Accommodation: Bending of the lens to focus on nearby objects
• Monocular depth cues referred to as pictorial depth cues
• Linear perspective: Apparent convergence of parallel lines in the environment
• Relative Size: More distant object made smaller
• Height in the plane: Objects that are placed higher/closer to the horizon line tend to be perceived as more distant
• Light and shadow: Most objects are lighted in ways that create clear patterns of light and shadow
• Overlap: (or interposition) occurs when one object partially blocks another.
• Texture Gradients: Changes in texture also contribute to depth perception
• Relative Motion: [Motion parallax] can be seen by looking out a window and moving your head side to side