2.1

Influences on Perception: Selective Attention

  • Selective Attention Definition and Mechanism

    • Selective attention acts like a flashlight beam, focusing conscious awareness on a minute aspect of all experienced sensory input.
    • Consciousness focuses on only one item at a time; multitasking between complex cognitive tasks (e.g., attending a lecture while reading/replying to text messages) involves rapid toggling rather than simultaneous conscious processing.
    • Sensory processing capacity versus conscious awareness:
    • Human sensory organs take in approximately 11,000,000 bits11,000,000\,\text{bits} of information per second (Wilson, 2002).
    • Conscious processing accounts for approximately 40 bits40\,\text{bits} per second.
    • The mind's unconscious track intuitively processes the remaining 10,999,960 bits10,999,960\,\text{bits} per second.

  • Research Methods in Selective Attention

    • Experimental Design Example:
    • Sample: 5050 students who watch a 10-minute10\text{-minute} lecture video.
    • Population: The broader population of students to whom findings might be generalized.
    • Study Design: Experimental, as participants are randomly assigned to distinct conditions (texting vs. silenced phones) prior to testing on lecture content via a post-video quiz.
    • Independent Variable (IV): Texting condition (replying to text messages vs. silenced phones).
    • Dependent Variable (DV): Quiz performance score evaluating lecture retention.
    • Causal Conclusions: Valid because random assignment controls for confounding variables, isolating the IV as the source of variation in the DV.

  • Auditory Selective Attention and the Cocktail Party Effect

    • Cocktail Party Effect: The ability to focus visual or auditory attention on a single voice within a noisy environment.
    • Cognitive Radar: Operating on the unconscious track, hearing one's name spoken in an unattended conversation instantly shifts that voice into conscious awareness.
    • Real-World Incident: In 2009, two Northwest Airlines pilots lost track of time while focused on laptops and personal conversation, ignoring air traffic controllers and overflying their Minneapolis destination by 150 miles150\,\text{miles}.

  • Selective Attention and Driving Accidents

    • Distraction Prevalence: 60%60\% of American drivers reported reading/sending texts or viewing phone maps while driving within the preceding month (Gliklich et al., 2016).
    • Attentional Switching Study: Participants spent 28 minutes28\,\text{minutes} in a room with internet and television access (Brasel & Gips, 2011):
    • Self-reported estimate: Participants guessed their attention switched 1515 times on average.
    • Operational definition: Attentional shifts operationally defined using eye-tracking measurements.
    • Objective result: Eye-tracking revealed an average of 120120 attentional switches (8×8\times the estimated amount).
    • Cognitive and Delay Tolls:
    • Rapid toggling between tasks creates switching delays when navigating complex environments (Rubenstein et al., 2001).
    • Brain activity in areas vital to driving decreases by an average of 37%37\% when a driver attends to a conversation (Just et al., 2008).
    • Fatality and Collision Statistics:
    • Distracted driving causes approximately 99 deaths per day in the United States (CDC, 2018a).
    • Video analysis of teen drivers showed passenger or phone distraction occurred immediately prior to 58%58\% of crashes (AAA, 2015).
    • Conversation with passengers increases crash risk 1.6×1.6\times above normal.
    • Cell phone use (including hands-free devices) increases crash risk 4×4\times above normal, equivalent to driving drunk (McEvoy et al., 2005, 2007).
    • Texting while driving increases collision risk by 23×23\times for long-haul truck drivers over an 18-month18\text{-month} observation period (Olson et al., 2009).
    • Academic Application: Dividing attention between studying and social networking reduces focus. Optimal learning strategy involves 25 minutes25\,\text{minutes} of uninterrupted study followed by a short break.

  • Inattentional Blindness

    • Definition: Failing to see visible objects when attention is directed elsewhere.
    • Basketball Video Demonstration: Ulric Neisser (1979), as well as Robert Becklen and Daniel Cervone (1983), showed a 1-minute1\text{-minute} video of two teams (33 players in black shirts, 33 in white shirts) passing a ball. Viewers counting passes by black-shirted players regularly failed to notice a woman carrying an umbrella sauntering across the screen (Mack & Rock, 2000).
    • Gorilla Experiment: Simons and Chabris (1999) repeated the pass-counting experiment with a gorilla-suited assistant who walked into the scene for 5–9 seconds5\text{--}9\,\text{seconds}, chest-thumped, and exited. 50%50\% of pass-counting participants missed the gorilla.
    • Radiology Study: When scanning lung images for cancer nodules, 2020 out of 2424 radiologists (83.3%83.3\%) failed to notice a tiny gorilla image superimposed on the upper right scan (Drew et al., 2013).
    • Practical Exploitations:
    • Magicians manipulate selective attention to perform misdirection (Teller, 2009).
    • Pickpockets utilize distraction; e.g., a Swedish psychologist in Stockholm was pickpocketed after being distracted by an exposing woman (Gallace, 2012).

  • Change Blindness

    • Definition: Failing to notice visual changes in the environment following a brief interruption.
    • Empirical Demonstrations: Viewers fail to notice the disappearance of a large Coca-Cola bottle, a rising railing, color changes in clothing, or the replacement of a direction-seeking stranger with a completely different person after two experimenters interrupt the conversation carrying a door (Chabris & Simons, 2010; Resnick et al., 1997; Simons & Levin, 1998).

Factors Shaping Perception: Expectations, Context, Motivation, and Emotion

  • Processing Orientations

    • Bottom-Up Processing: Begins at sensory receptors and works up to brain integration of sensory input.
    • Top-Down Processing: Constructs perceptions from sensory input by drawing on experience, schemas, and expectations.

  • Perceptual Set

    • Definition: A mental predisposition or assumption that affects (top-down) what we see, hear, taste, touch, and smell.
    • Visual Perceptual Set:
    • Boring (1930) ambiguous figures: Exposure to unambiguous drawings establishes expectations, leading viewers to perceive either an old woman or a young woman's profile in an identical ambiguous image. Similarly, reading left-to-right leads viewers to see a middle figure as the letter B, while reading top-to-bottom leads to perceiving the number 13.
    • Loch Ness Monster Photo: In 1972, a British newspaper published unretouched photos of a supposed monster in Loch Ness. Expectations led readers to perceive a monster, whereas skeptical re-examination revealed a curved tree limb (Campbell, 1986).
    • Auditory Perceptual Set:
    • Mishearing spoken phrases based on expectation (e.g., 'stuffy nose' vs. 'stuff he knows').
    • An airline co-pilot mistakenly raised the landing gear before takeoff after hearing 'Cheer up' and expecting 'Gear up' (Reason & Mycielska, 1982).
    • Misheard lyrics (mondegreens), such as 'José, can you see?' instead of 'O say can you see' (KissThisGuy.com).
    • Taste Perceptual Set:
    • Preschoolers preferred identical french fries by a 6–to–16\text{--}\text{to}\text{--}1 margin when served in a McDonald's branded bag compared to a plain white bag (Robinson et al., 2007).
    • MIT students sampling free beer preferred vinegar-laced 'MIT Brew' unless they were told in advance about the vinegar, in which case expectations led to lower taste ratings (Lee et al., 2006).
    • Schemas and Stereotypes:
    • Schemas organize and interpret unfamiliar information.
    • Cultural, gender, and social stereotypes shape perception top-down. For example, adults and children perceive an infant named 'David' as bigger and stronger than the exact same infant when introduced as 'Diana' (Stern & Karraker, 1989).

  • Context Effects

    • Auditory Context: Hearing 'eel is on the wagon' leads the brain to perceive 'wheel', whereas 'eel is on the orange' leads to perceiving 'peel' (Grossberg, 1995).
    • Cultural Context: Rural East Africans viewing a drawing perceived a woman balancing a metal box or can on her head under a tree. Westerners, accustomed to tap water and box-like architecture with corners, perceived the family indoors under a window (Gregory & Gombrich, 1973).
    • Social Context: Driving versus walking changes perception of crosswalk interactions (Lee Ross; Jaffe, 2004).
    • Blinded Auditory Evaluation: In blind tests, expert solo violinists preferred modern violins over multi-million-dollar classic Italian violins (Fritz et al., 2017).
    • Blind and Double-Blind Controls:
    • Single-Blind Procedure: Participants are uninformed about which treatment condition they are receiving.
    • Double-Blind Procedure: Neither the participants nor the research staff know which condition participants are in.

  • Motivational Influences

    • Desirability Bias: Desirable items (e.g., a water bottle viewed by a thirsty individual) are perceived as physically closer (Balcetis & Dunning, 2010).
    • Interpersonal Proximity: Heterosexual men judge women who are physically closer as more attractive (Shin et al., 2019).
    • Physical Effort Demands:
    • A hill appears steeper when carrying a heavy backpack or when fatigued (Burrow et al., 2016; Philbeck & Witt, 2015; Proffitt, 2006a,b).
    • Weight loss causes stairs and hills to appear less steep (Taylor-Covill & Eves, 2016).
    • Athletic Performance:
    • A softball appears larger to players who are hitting well (Witt & Proffitt, 2005).
    • Visually focusing on a target makes it appear larger, which reciprocally improves performance (Witt et al., 2012).

  • Emotional Influences

    • Auditory Interpretation: Listening to sad music inclines listeners to perceive homophonic words with sad meanings (e.g., 'mourning' instead of 'morning', 'die' instead of 'dye', 'pain' instead of 'pane') (Halberstadt et al., 1995).
    • Word Recognition: Upbeat music (e.g., Beyoncé's 'Single Ladies') speeds up identification of positive emotion words (Tay & Ng, 2019).
    • Threat Perception: Angry individuals are more likely to misperceive neutral objects as weapons (Baumann & DeSteno, 2010).
    • Attraction: Hunger increases the perceived attractiveness of larger body types (Saxton et al., 2020).
    • Subliminal Priming: Brief, subliminal exposure to a scowling face leads individuals to perceive a subsequent neutral face as less attractive and likable (Anderson et al., 2012).

Gestalt Principles and Perceptual Organization

  • Gestalt Psychology Fundamentals

    • Gestalt: A German term meaning 'form' or 'whole'. Gestalt psychologists emphasized that the brain organizes sensations into an integrated whole.
    • Core Principle: In perception, the whole may exceed the sum of its parts. Perception is an active construction, not a passive recording.

  • Sensation versus Perception Distinction (Necker Cube)

    • Necker Cube: An ambiguous figure constructed from eight hexagons containing three converging white lines (Bradley et al., 1976).
    • Sensory Input: The physical sensation consists strictly of line segments and uncolored wedges on a page.
    • Perceptual Output: The mental construction yields a continuous 3D cube floating in space, which periodically shifts orientation in conscious awareness.

  • Form Perception: Figure-Ground Separation

    • Figure-Ground: The organization of the visual field into objects (the figures) that stand out from their surroundings (the ground).
    • Cross-Modal Application: Applies to vision (words as figure, white page as ground) and audition (a single attended voice as figure, ambient noise as ground).
    • Reversibility: Stimuli such as the classic Rubin vase/faces illusion demonstrate that the same visual input can yield reversing figure-ground relationships.

  • Form Perception: Grouping Principles

    • Proximity: Grouping nearby figures together. Six individual lines arranged as three pairs are seen as three sets of two lines.
    • Similarity: Grouping similar items together. An array of circles is grouped into distinct vertical or horizontal columns based on color.
    • Closure: Filling in visual gaps to construct a complete, enclosed object. Mind-generated contours (such as an illusory white triangle blocking incomplete black circles) disappear if thin lines close off the open circles.
    • Impossible Structures: Gestalt grouping principles (proximity and closure) lead observers to perceive impossible 3D objects, such as the illusion of a continuous doghouse.

Spatial Depth Cues and Motion Perception

  • Depth Perception

    • Definition: The ability to see objects in three dimensions despite the images that strike the retina being two-dimensional; allows distance estimation.
    • Visual Cliff Research:
    • Conducted by Eleanor Gibson and Richard Walk (1960) at Cornell University using a miniature cliff with a glass cover.
    • Participants: Infants aged 6–14 months6\text{--}14\,\text{months}.
    • Results: Most infants refused to crawl onto the glass drop-off area when coaxed by parents, demonstrating depth perception.
    • Developmental & Evolutionary Findings: Crawling experience increases height wariness as infants gaze downward at upcoming hazards (Karen Adolph & Hoch, 2019; Adolph et al., 2014; Campos et al., 1992; Kretch et al., 2014). Mobile newborn animals without prior visual experience (kittens, 1-day-old goats, newly hatched chicks) also refuse to cross the visual cliff.

  • Binocular Cues

    • Definition: Depth cues that depend on the simultaneous use of two eyes.
    • Convergence: Neuromuscular cue where the eyes rotate inward to focus on closer objects, combined by the brain to gauge distance.
    • Retinal Disparity: The difference between the two images generated by the space between the eyes. The brain compares images from both retinas; greater disparity indicates closer proximity.
    • Floating Finger Sausage Demonstration: Holding index fingers 12 cm12\,\text{cm} (5 inches5\,\text{inches}) in front of the eyes with tips 1 cm1\,\text{cm} apart creates a floating 'sausage' segment due to retinal disparity.
    • Applications: 3D cinema technologies and 3D street paintings (e.g., Saumya Pandya Thakkar and Shakuntala Pandyaand's crosswalk art).

  • Monocular Cues

    • Definition: Depth cues available to either eye individually, essential at distances ranging from 10 m10\,\text{m} to over 100 m100\,\text{m} where retinal disparity becomes negligible.

  • Motion Perception

    • Default Motion Assumptions: The brain computes motion on the assumption that enlarging objects are approaching and shrinking objects are retreating.
    • Developmental Lag: Young children have underdeveloped capabilities to accurately judge the speed of approaching (enlarging) vehicles, raising pedestrian collision risks (Wann et al., 2011).
    • Size-Speed Illusion: Larger objects moving at the same speed as smaller objects appear to move slower (e.g., jumbo jets appearing slower than small planes, trains appearing slower than cars).
    • Visual Interruptions: Blinking interrupts vision for 0.1 second0.1\,\text{second} roughly 1515 times per minute (15,00015,000 unnoticed interruptions per day) without disrupting motion continuity (Grossman et al., 2019).
    • Stroboscopic Movement: Perception of continuous motion from a rapid series of slightly varying still images (e.g., projection at 24 frames/second24\,\text{frames/second} in animation).
    • Phi Phenomenon: An illusion of movement created when two or More adjacent stationary lights blink on and off in quick succession.
    • Autokinetic Effect: The apparent movement of a stationary point of light in an otherwise dark room, caused by tiny, involuntary eye movements.

Perceptual Constancies in Visual and Auditory Domains

  • Perceptual Constancy Overview

    • Definition: A top-down process enabling the perception of objects as unchanging in shape, size, brightness, and color despite changes in sensory illumination, perspective, and distance.

  • Color Constancy

    • Mechanism: Perceiving consistent color in familiar objects under changing illumination.
    • Ecological Perspective: Context governs color perception (James Gibson, 1979).
    • Relative Reflectance: Wavelengths reflected by an indoor blue poker chip match those of a sunlit gold chip (Jameson, 1985). Color is not an inherent trait of an object in isolation, but a brain computation relative to surrounding context.

  • Brightness (Lightness) Constancy

    • Relative Luminance: The amount of light an object reflects relative to its surroundings.
    • Reflectance Factors: White paper reflects 90%90\% of light; black paper reflects 10\%$.\n * **Contextual Shifts**: Sunlit black paper reflects 100\times more light than indoor white paper, yet looks black because surrounding sunlit objects reflect proportionally more light (McBurney & Collings, 1984).\n * **Checkerboard Illusion**: Edward Adelson's illusion shows identical grey shades (Square A and Square B) appearing completely different due to surrounding shadows and contrast contexts.\n\n* **Shape and Size Constancies**\n * **Shape Constancy**: Perceiving the form of familiar objects as constant despite changes in retinal image (e.g., an opening door projects an increasingly trapezoidal retinal image but is perceived as rectangular) (Li & DiCarlo, 2008).\n * **Size Constancy**: Perceiving an object as having a constant size regardless of distance.\n * **Size-Distance Interplay**: Perceived distance informs size estimation, and known size informs distance estimation.\n * **Moon Illusion**: The horizon Moon looks up to 50\% larger than the zenith Moon. Monocular distance cues make the horizon Moon seem farther away; the brain infers that a more distant object projecting the same retinal size must be larger (Kaufman & Kaufman, 2000).\n\n* **Auditory Perceptual Constancy and Organization**\n * Unfamiliar languages sound like continuous streams of acoustic energy.\n * Familiar languages are organized automatically into distinct words (e.g., parsing the letter string 'THEDOGATEMEAT' into 'The dog ate meat').\n\n# Perceptual Interpretation, Critical Periods, and Adaptation\n\n* **Philosophical Debates on Perception**\n * **Immanuel Kant (1724–1804)**: Argued for nativism (Nature), asserting that knowledge and perceptual organization stem from inborn capacities.\n * **John Locke (1632–1704)**: Argued for empiricism (Nurture), asserting that the mind begins as a blank slate (*tabula rasa*) and perception is learned through experience.\n * **Molyneux’s Problem**: William Molyneux asked Locke whether a man born blind who learned to identify a sphere and cube by touch could visually distinguish them if his sight were restored. Locke answered 'No', concluding he would lack visual experience.\n\n* **Restored Vision and Sensory Restriction**\n * **Congenital Cataract Studies**: Individuals born blind due to cataracts who gained sight in adulthood (Gandhi et al., 2017; Gregory, 1978; von Senden, 1932):\n * Innate capacities: Could immediately distinguish figure from ground, differentiate colors, and distinguish human faces from non-faces.\n * Acquired capacities: Could not visually recognize objects previously known exclusively through touch.\n * **The Case of Mike May**: Blinded at age 3 by an explosion; underwent cornea restoration decades later. Could see motion and dust floating in sunlight, but could not recognize faces or expressions visually without relying on isolated feature cues like hair (Abrams, 2002; Gorlick, 2010; Huber et al., 2015).\n * **Animal Deprivation Experiments**: Infant kittens and monkeys fitted with goggles allowing only diffuse, unpatterned light (Hubel & Wiesel, 1963):\n * Results: Retinal signals reached the visual cortex, but without early structured stimulation, cortical networks failed to form normal connections, leaving the animals functionally blind to shape.\n * **Ethical Guidelines**: Animal research must adhere to APA ethical standards regarding humane treatment.\n * **Critical Period**: An optimal period early in life when exposure to specific sensory stimuli or experiences is required for normal perceptual development (Chatterjee, 2015; Gandhi et al., 2014).\n * **Adult Resilience**: Cataract removal or eye patching in adulthood causes no permanent neural damage because early critical periods were successfully completed.\n\n* **Perceptual Adaptation**\n * **Definition**: In vision, the ability to adjust to an artificially displaced or inverted visual field.\n * **Species Differences**: Baby chicks fitted with distorting lenses cannot adapt and continue pecking where food erroneously appears to be (Hess, 1956; Rossi, 1968).\n * **Human Displacement Adaptation**: Humans wearing glasses that shift vision 40^\circ to the left initially misthrow objects or veer left, but adapt within minutes. Removing the glasses produces an aftereffect in the opposite direction (sailing off to the right) before quick readaptation occurs.\n * **Inversion Experiments**:\n * George Stratton (1896) invented optical headgear that flipped the visual field left-to-right and top-to-bottom, wearing it continuously for 8\,\text{days}$$.
    • Symptoms: Initial disorientation, nausea, depression, and severe motor impairment.
    • Outcome: By day 8, Stratton achieved fluid motor coordination and readapted quickly upon removing the device.
    • Subsequent Studies: Replicated by individuals performing active tasks like motorcycle riding, skiing, and flying airplanes while wearing inverting goggles (Dolezal, 1982; Kohler, 1962; Hubert Dolezal).
    • Perceptual Maintenance: Professional practice (e.g., radiologists evaluating complex visual scans) continuously shapes, maintains, and sharpens visual recognition pathways throughout life (Hussain, 2020).