Psych 384: Sensation and Perception. Dr. Matthews

Sensation

The ability to detect a stimulus and turn that detection into a private experience.

Perception

The act of giving meaning to a detected sensation.

Transduction

The conversion of a physical stimulus, such as light or sound, into a neural response through the activity of sensory receptors.

Interoception

The sense of the internal state of the body.

Method of limits

A psychological method in which the particular dimension of a stimulus is varied incrementally until the participant responds differently.

Just noticeable difference (JND)

The smallest detectable difference between two stimuli.

Psychophysics

The science of defining quantitative relationships between physical and psychological events.

Absolute Threshold

The minimum amount of stimulation necessary for a person to detect a stimulus 50% of the time.

Weber's law

The principle that states the just noticeable difference is a constant fraction of the comparison stimulus.

Fechner's law

The principle that says the magnitude of subjective sensation increases proportionally to the logarithm of the stimulus intensity.

Signal detection theory

A psychophysical theory that quantifies the response of an observer to the presence of a signal in the presence of noise.

Cranial Nerves

Twelve pairs of nerves that originate in the brainstem and reach sense organs and muscles through openings in the skull.

Neuron

The fundamental type of cell in the nervous system, collecting signals from sense organs and transmitting signals to muscles.

Neurotransmitter

A chemical substance used in neuronal communication at synapses.

Magnetoencephalography (MEG)

A technique that measures changes in magnetic activity across populations of many neurons in the brain.

Functional Magnetic Resonance Imaging (fMRI)

An imaging technology that measures localized patterns of activity in the brain.

Bloch's Law

The detection threshold for a brief flash of light is the product of the luminance of the light and its duration.

Cranial Nerve I: Olfactory

The first cranial nerve responsible for the sense of smell.

Cranial Nerve II: Optic

The second cranial nerve that carries visual information from the retina.

Cranial Nerve VII: Facial

The seventh cranial nerve responsible for taste sensations from the anterior tongue and facial expressions.

Sensation

The process of detecting physical energy or stimuli from the environment through sensory organs and converting that detection into private neural experiences.

Perception

The cognitive process of selecting, organizing, and interpreting raw sensory inputs to give them meaningful interpretation and subjective experience.

Transduction

The biological conversion of physical energy or environmental stimuli—such as photons, sound waves, or chemical molecules—into electrical signals by specialized sensory receptor cells.

Interoception

The sensory system and sense responsible for perceiving the physiological condition and internal signals of the body, such as heart rate, hunger, respiration, and visceral sensations.

Psychophysics

The scientific discipline that investigates quantitative and mathematical relationships between physical properties of stimuli and the resulting psychological or subjective sensations.

Absolute Threshold

The minimum intensity of a stimulus required for a sensory system to detect its presence 50% of the time under controlled conditions.

Just Noticeable Difference (JND)

The smallest magnitude of change in stimulus intensity that an observer can reliably discriminate as being different from a standard stimulus.

Method of Limits

A psychophysical measurement technique in which a specific stimulus property is varied incrementally in ordered ascending or descending steps until the participant reports a change in perception.

Method of Constant Stimuli

A psychophysical procedure where a predetermined set of stimulus intensities is presented many times in random order to determine detection thresholds or psychometric functions.

Method of Adjustment

A psychophysical technique where the participant directly controls and continuously manipulates the stimulus intensity until it is barely detectable or matches a comparison standard.

Weber's Law

The psychophysical principle stating that the difference threshold is a constant fraction of the comparison stimulus intensity, represented as $\frac{\Delta I}{I} = K$.

Fechner's Law

The psychophysical principle describing subjective sensation magnitude as proportional to the logarithm of physical stimulus intensity, expressed as $S = k \log(I)$.

Stevens' Power Law

A psychophysical relationship describing subjective magnitude as a power function of stimulus intensity, expressed as $S = a I^b$, accommodating non-linear sensation changes across various sensory modalities.

Signal Detection Theory (SDT)

A framework for measuring perceptual sensitivity and decision-making biases by quantifying an observer's ability to discriminate target signals from background noise.

Criterion ($\beta$)

In signal detection theory, the internal threshold or bias setting an observer uses to decide whether a detected response was generated by a signal plus noise versus noise alone.

Sensitivity ($d'$)

In signal detection theory, the quantitative measure of an observer's perceptual ability to distinguish between target signals and background noise, independent of decision bias.

Bloch's Law

The principle of visual temporal integration stating that the detection threshold for a brief flash of light is determined by the constant product of luminance and exposure duration ($I \times t = C$).

Neuron

The primary electrical and signaling cell of the nervous system, responsible for receiving, integrating, and transmitting electrochemical information across specialized networks.

Neurotransmitter

A specialized chemical messenger released by presynaptic terminal boutons to transmit signals across synaptic clefts to target cells.

Cranial Nerves

Twelve paired sets of peripheral nerves originating directly from the brainstem and brain, passing through foramina in the skull to innervate sensory organs and facial structures.

Cranial Nerve I (Olfactory Nerve)

The first pair of cranial nerves composed entirely of sensory fibers that transmit chemosensory information regarding odorants from the nasal mucosa to the brain.

Cranial Nerve II (Optic Nerve)

The second pair of cranial nerves consisting of sensory fibers originating from retinal ganglion cells that convey visual information to the brain.

Cranial Nerve V (Trigeminal Nerve)

The fifth pair of cranial nerves supplying somatosensory innervation to the face, scalp, and mouth, as well as motor control to the muscles of mastication.

Cranial Nerve VII (Facial Nerve)

The seventh pair of cranial nerves mediating taste sensation from the anterior two-thirds of the tongue and providing motor control for facial expression muscles.

Cranial Nerve VIII (Vestibulocochlear Nerve)

The eighth pair of cranial nerves conveying auditory and vestibular information from the inner ear to the brain stem for hearing and balance control.

Functional Magnetic Resonance Imaging (fMRI)

A non-invasive neuroimaging technique that tracks blood-oxygenation-level-dependent (BOLD) signal changes to map active brain regions with high spatial resolution.

Magnetoencephalography (MEG)

A non-invasive neuroimaging technique that measures weak magnetic fields generated by synchronized ionic electrical currents in large populations of neurons, offering high temporal resolution.