Sensation and Perception Exam 1

Perception (stage)

Becoming consciously aware of a stimulus

PP relationship

The stimulus ↔ perception linkage measured with psychophysical methods

PH1 relationship

The stimulus ↔ physiological response linkage

PH2 relationship

The physiological response ↔ perception linkage

Describing (response)

Verbally reporting a perceived quality (e.g.

Recognizing (response)

Categorizing or identifying a stimulus

Detecting (response)

Judging the presence or absence of a stimulus

Perceiving magnitude

Estimating the intensity or size of a stimulus

Searching

Locating a target among distractors

Response criterion

The internal decision threshold for saying a stimulus is present

Perception

Conscious experience created by the brain from sensory input and prior knowledge

Perceptual process

The sequence stimulus → electricity → experience/action → knowledge that produces perception

Environmental stimulus

Everything in the environment that could be sensed at a moment

Attended stimulus

The specific environmental item you focus your attention on

Stimulus on the receptors

The pattern of energy that falls on sensory receptors (e.g.

Transduction

Conversion of environmental energy (e.g.

Transmission

Movement of electrical signals from receptors through neurons to the brain

Processing

Neural interactions that transform and interpret signals across networks

Perception (stage)

Becoming consciously aware of a stimulus

Recognition

Identifying or categorizing what the perceived stimulus is

Action

Behavioral response guided by perception (e.g.

Knowledge

Prior information

Bottom-up processing

Data-driven processing that starts at the receptors

Top-down processing

Knowledge-based processing that uses expectations and experience

Cognitive influences

Effects of memory/expectations on perception and neural activity

Psychophysical approach

Studying the relationship between physical stimuli and perceptual experience

Physiological approach

Studying relationships among stimuli

Absolute threshold

Minimum stimulus intensity detected 50% of the time

Difference threshold (JND)

Smallest detectable change in stimulus intensity

Weber’s Law

The JND is a constant proportion of the standard (ΔI / I = K)

Magnitude estimation

Judging perceived intensity across a range of physical intensities

Stevens’ power law

P = K·Sⁿ relating perceived magnitude (P) to physical intensity (S)

Reaction time

Time from stimulus onset to response (simple vs. choice RT)

Signal detection theory

Framework separating sensitivity from decision criterion/bias

Hit

“Yes” response when the signal is present

Miss

“No” response when the signal is present

False alarm

“Yes” response when the signal is absent

Correct rejection

“No” response when the signal is absent

Response criterion

Internal decision threshold for saying a stimulus is present

Method of limits

Ascending/descending series used to estimate thresholds

Method of adjustment

Observer adjusts intensity to the just-detectable level

Method of constant stimuli

Randomized

Neuron

Cell that receives

Cell body (soma)

Neuron’s metabolic center containing the nucleus

Dendrites

Branches that receive inputs from other neurons

Axon (nerve fiber)

Long process that conducts action potentials

Receptor (sensory)

Specialized neuron that transduces environmental energy

Photoreceptors

Light-sensitive receptors in the eye (rods and cones)

Hair cells

Mechanoreceptors for hearing that transduce vibration

Mechanoreceptors

Touch receptors that transduce pressure/stretch

Olfactory receptors

Smell receptors for airborne chemicals

Taste receptors

Receptors on the tongue for dissolved chemicals

Microelectrode

Fine electrode for recording from single neurons

Resting potential

About –70 mV; stable internal voltage when the neuron is inactive

Action potential

• spike that propagates along the axon

Propagated response

Action potential maintains its size as it travels down the axon

All-or-none principle

Action potentials have fixed amplitude; stronger stimuli increase rate

Rate of firing

Information coded by impulses per second (spikes/second)

Refractory period

Brief time after a spike when no new spike can occur

Spontaneous activity

Baseline firing without external stimulation

Synapse

Gap between neurons where chemical transmission occurs

Neurotransmitter

Chemical released into the synapse to influence the next neuron

Excitatory transmitter

Causes depolarization

Inhibitory transmitter

Causes hyperpolarization

Depolarization

Positive shift in membrane potential (e.g.

Repolarization

Return toward resting potential (e.g.

Sodium–potassium pump

Active transport restoring Na⁺/K⁺ gradients after spikes

Neural circuit

Interconnected group of neurons that process information

Convergence

Multiple neurons sending input to a single neuron

Receptive field

Region on a sensory surface where stimulation changes a neuron’s firing

Electromagnetic spectrum

The full range of electromagnetic energy; visible light is a small band

Wavelength

Distance between peaks of a wave; determines perceived color for light

Visible light

~400–700 nm wavelength range that humans can see

Photon

Smallest packet (quantum) of light energy

Cornea

Transparent front surface providing most of the eye’s focusing power (fixed)

Lens

Adjustable focusing element that fine-tunes focus on the retina

Retina

Light-sensitive layer containing rods and cones

Optic nerve

Bundle of ganglion cell axons carrying signals to the brain

Rods

Photoreceptors specialized for dim light; high sensitivity

Cones

Photoreceptors specialized for bright light and color/detail

Accommodation

Lens shape change via ciliary muscles to focus near/far objects

Near point

Closest distance at which accommodation can maintain sharp focus

Presbyopia

Age-related loss of lens flexibility that increases the near point

Myopia (nearsightedness)

Distant objects blur because focus is in front of the retina

Axial myopia

Eye is too long

Refractive myopia

Cornea/lens bends light too strongly

Hyperopia (farsightedness)

Near objects blur because focus is behind the retina

LASIK

Surgical reshaping of the cornea to correct refractive errors

Opsin

Protein component of the visual pigment embedded in receptor discs

Retinal

Light-sensitive molecule attached to opsin that isomerizes with light

Isomerization

Shape change of retinal when absorbing a photon; triggers transduction

Enzyme cascade

Amplifying biochemical chain reaction following pigment activation

Fovea

Small central retinal area with only cones; highest acuity

Peripheral retina

Area outside the fovea with many rods; higher sensitivity and motion detection

Macular degeneration

Degeneration of fovea/nearby cones causing central vision loss

Retinitis pigmentosa

Genetic degeneration starting with rods

Blind spot

Location where the optic nerve exits; no receptors

Dark adaptation

Increase in visual sensitivity over time in darkness

Rod–cone break

Point during dark adaptation when rods become more sensitive than cones

Rod monochromat

Person with only rods; used to study rod adaptation in darkness