Sensation and Perception: An Overview

• Sensation involves sensory organs (eyes, ears, nose, mouth, skin) detecting stimuli.

Sensation vs. Perception

• Data-based processing is earlier and more biological than other forms of processing.
• Psychophysics studies the relationship between physical stimuli and psychological experiences.
• Absolute threshold is the minimum stimulation needed to detect a stimulus 50% of the time.
• Just Noticeable Difference (JND) / Difference Threshold is the minimum difference between stimuli required for detection 50% of the time.
• Weber's Law states that JNDs are proportional to the size of the original stimuli.
• Human sensory systems include vision/hearing (energy), smell/taste (chemical), and somatosenses (touch, balance, kinesthesis).
• Receptor cells for each sense stimulate neurons in the CNS.
• Receptor cells translate sensory input (sights, sounds, smells) into action potentials.

The Human Eye

• The cornea is a transparent covering that focuses light onto the back of the eye.
• The pupil controls the amount of light entering the eye.
• The iris is the colored part of the eye.
• The lens becomes thinner to focus on distant objects.
• The retina contains receptor cells (rods and cones) and is located at the back of the eye.
• The central fovea contains only cones.
• The optic disc has no rods or cones, creating a blind spot.
• The optic nerve acts as a power cord, transmitting visual information.
• Receptor cells for vision include rods and cones.
• Rods are concentrated in the periphery of the retina, enable black and white vision, and are most active in dim illumination.
• Cones are concentrated in the fovea, enable color vision, and are most active in bright illumination.

The Human Ear

• Sound waves travel through the pinna (funnel), auditory canal, eardrum, and ossicles.
• The cochlea contains receptor cells (hair cells).
• The auditory nerve transmits auditory information to the brain.
• Receptor cells for hearing are hair cells.
• The stirrup vibrates, causing the jello in the cochlea to move/jiggle..
• Hair cells in the cochlea fire action potentials and the thalamus distributes frequency information
• The auditory cortex interprets sound, leading to perception.
• Perception is the organization and interpretation of sensory stimuli by the brain.
• Perception involves knowledge-based processing and creates a "mental image".
• It includes processing, organizing, and interpreting sensory signals, resulting in an internal representation of stimuli and perceptual organization.

Bottom-Up & Top-Down Processing

• Bottom-up processing starts with sensory input, where the brain interprets raw data without prior knowledge.
• Top-down processing involves using prior knowledge, experiences, and expectations to interpret sensory information.
• Perceptual parsing is the process by which the brain organizes visual elements into meaningful groups or objects and helps separate objects from the background (figure-ground distinction).

Gestalt Principles of Organization

• Gestalt principles are rules that explain how people naturally organize visual information into meaningful patterns or wholes.
• Examples include proximity, similarity, closure, continuity, and common fate.

Depth Cues

• Depth cues are visual signals that help us perceive depth and distance.
• They include monocular cues (e.g., linear perspective, texture gradient) and binocular cues (e.g., retinal disparity, convergence).
• Perceptual Constancies refers to our ability to perceive objects as unchanging despite variations in sensory input.
• Examples include size, shape, brightness, and color constancy.

Visual Pathway

• Light stimulates photoreceptor cells (rods and cones) in the retina.
• These cells transmit signals to bipolar cells, which relay signals to ganglion cells.
• Axons of ganglion cells bundle together to form the optic nerve, which carries visual information to the brain.

Consciousness, Sleep and Dreams

• Circadian rhythms are daily biological cycles that are about 24 hours long.
• Circadian rhythms are regulated by the suprachiasmatic nuclei (SCN) in the hypothalamus (nature).
• Environmental factors like the day-night cycle also affect circadian rhythms (nurture).
• A typical night's sleep is from 11pm-7am.
• Sleep researchers use EEG's
• Sleep stages include N1 (first falling asleep, 10-15 mins), N2 (transitional, 40% of time), and N3 (deep sleep, slow wave sleep).
• We cycle through all the stages during the course of the night.
• More N3 (deep sleep) occurs earlier in the night.
• More and longer REM sleep occurs later in the night.
• REM sleep is often called paradoxical sleep and includes rapid eye movement, vivid dreaming, physiological arousal, and muscle paralysis.
• Changes in REM sleep with age: As people get older, there are fewer hours of sleep and less time spent in the REM stage.
• Restorative theory suggests that sleep allows us to recharge our bodies and recover from fatigue.
• Evolution theory suggests that sleep's main purpose is to increase a species' chances of survival.
• Consolidation theory suggests that sleep helps strengthen neuronal connections for learning and memory.

Sleep Disorders

• Insomnia is a chronic inability to sleep normally, characterized by difficulty falling asleep/onset, frequent waking, difficulty returning to sleep, or early morning awakening, and can be caused by anxiety and depression.
• Narcolepsy is an irresistible compulsion to sleep during the daytime.
• Sleep apnea causes a person to stop breathing while sleeping.
• Activation synthesis theory suggests that the brainstem (pons) bombards higher brain centers with random neural activity, which the cerebral cortex interprets as a dream.
• Freud's psychoanalytic theory suggests that dreams symbolize fulfillment (royal road to unconsciousness) and have manifest (story narrative) vs. latent (hidden, underlying meaning) content.

Mind-Altering Drugs

• Psychoactive drugs are chemicals that affect mental processes and behavior by temporarily changing conscious awareness.
• Tolerance occurs when an individual requires greater doses of drugs to get the same effect.
• Withdrawal occurs after reducing or ceasing drug intake, causing physical or psychological symptoms.
• Tolerance + withdrawal = physiological dependence (addiction).
• Depressants/sedatives decrease CNS activity and include alcohol, barbiturates (seconal), and benzodiazepines (valium).
• Stimulants increase CNS activity and include amphetamines, caffeine, nicotine, cocaine/crack, and Ecstasy (MDMA).
• Hallucinogens include marijuana, LSD, and PCP.
• Opiates (narcotics) include morphine, heroin, and codeine.
• Learning is a relatively enduring change in behavior that results from experience.
• Types of learning include classical conditioning (learning via associations between two stimuli), operant conditioning (learning via consequences), and observational learning (learning via imitation).

Classical Conditioning

• Ivan Pavlov (1849-1936) was a Russian psychologist who studied digestion in dogs.
• Pavlov's dog salivated in anticipation of being fed and events cued the dogs that feeding was imminent.
• An unconditioned stimulus does not require any prior learning (comes 2nd).
• An unconditioned response is an action in response to the stimulus.
• A conditioned stimulus becomes associated with the US (comes 1st).
• A conditioned response is the unconditioned response in response to the conditioned stimulus.

Major Phenomena of Classical Conditioning

• Acquisition (CS+US) is the initial learning of a conditioned response (CR).
• Acquisition includes the learning curve, which shows how quickly learning takes place, and steep learning curve happens when learning happens quickly
• Extinction (CS alone) is the diminishing of a conditioned response and is when the CS is repeatedly presented without the US.
• Spontaneous recovery is the reappearance, after a pause, of an extinguished response (CR) but it comes back not as strong.
• Generalization is the tendency for stimuli similar to the original CS to elicit a CR and happens when an organism learns to respond to more than one CS with a CR.
• Discrimination happens when an organism learns to discriminate between CS and stimuli that do not signal a US.
• John B. Watson's "Little Albert" experiment demonstrated that emotional responses can be classically conditioned by associating a neutral stimulus (a white rat) with an unconditioned stimulus (a loud noise) to create a conditioned fear response.

Operant Conditioning

• Reward acts increase frequency
• Punishment acts decrease frequency
• Positive reinforcement strengthens a response by presenting a stimulus while Negative Reinforcement strengthens a response by removing an aversive stimulus.
• Positive punishment weakens a response by presenting a stimulus, while negative punishment weakens a response by removing a stimulus.
• Reinforcers guide behavior toward closer and closer approximations of the desired behavior.
• Complex targets can be shaped by rewarding successive approximations, rewarding "baby steps."
• Primary reinforcers are innate reinforcers, such as biological needs (food, water), while Secondary reinforcers serve as reinforcers through their repeated pairing with primary reinforcers
• Reinforcement schedules dictate how often reinforcement should be given.

Reinforcement Schedules

• Continuous reinforcement reinforces behavior each and every time it occurs.
• Partial reinforcement reinforces behavior intermittently and is administered through reinforcement schedules (ratio and interval).
• Ratio schedules are based on the number of responses
• Interval schedules are based on time since the last reward.
• Observational learning involves four steps: paying attention to a model's behavior, retaining information in memory, being physically capable of reproducing the behavior, and being motivated to display the behavior.

Memory

• Explicit memory involves conscious effort, while implicit memory does not.
• Declarative memory is memory for facts and events (episodic/semantic), while procedural memory is memory for how to do things (skills/behaviors).
• Memory process includes encoding (data entry), storage ("save"), and retrieval ("open").
• Information processing model involves sensory memory (iconic/echoic), short-term memory (working memory, limited capacity), and long-term memory (nearly unlimited capacity, consolidation).
• The serial position effect includes the primacy effect (enhanced recall of information at the beginning of the list, rehearsal) and the recency effect (enhanced recall of information at the end of the list, in short-term memory).
• We can typically hold 5-9 pieces of information in short-term memory.
• Chunking (reconfiguring items by grouping them) can help us hold more pieces of information.
• Levels of processing theory suggests that shallow (visual), intermediate (rhyme), and deep (semantic/meaning) processing influence memory.
• Ebbinghaus's forgetting curve shows that we lose ⅔ of information within the first hour if we don't encode it.
• Interference includes proactive (old information interferes with new information) and retroactive (new information interferes with old information).
• Retrograde amnesia is a loss of previously stored memories, but the ability to form new memories exists.
• Anterograde amnesia can retrieve old memories but cannot form new memories.
• Regions of the brain such as the cerebellum, cerebral cortex (sensory memories), amygdala and hippocampus (declarative memories) and the hippocampus (factual memories) are involved in memory.
• Primary reinforcers are innately reinforcing (food, water), while secondary reinforcers serve as reinforcers through their repeated pairings with primary reinforcers.