Lecture 4: Sensation and Perception

Comprehensive practice flashcards covering sensation and perception, psychophysics, vision, audition, somatosensation, pain, olfaction, and gustation from Lecture 4 of PSYC 1010.

What is the primary distinction between sensation and perception?

Sensation is the simple stimulation of a sense organ as parts of the body interact with the physical world, whereas perception is the organization, identification, and interpretation of a sensation to form a mental representation.

What is transduction in the context of sensory systems?

Transduction is the process where sensors in the body convert physical signals from the environment into encoded neural signals that are transmitted to the central nervous system.

What is sensory adaptation, and why is it biologically beneficial?

Sensory adaptation is the decline in sensitivity to prolonged, unchanging stimulation over time. It reduces constant environmental distractions so sensory systems can respond more strongly to changes that signal a need for action.

What visual adaptation phenomenon is demonstrated when fixating on the central black dot causes the surrounding gray field to fade away?

Troxler Fading.

How is psychophysics defined?

Psychophysics refers to methods that systematically relate the physical characteristics of a stimulus to an observer’s perception.

What is an absolute threshold in sensory measurement?

The minimal intensity needed to just barely detect a stimulus, typically defined as the point of detection on $50\%$ of trials.

What are the classic absolute thresholds for vision and hearing?

For vision, detecting a candle flame $30\text{ miles}$ away on a clear, dark night; for hearing, detecting a clock's tick $20\text{ feet}$ away when all is quiet.

What are the classic absolute thresholds for touch, smell, and taste?

For touch, a fly’s wing falling on the cheek from $1\text{ centimetre}$ away; for smell, a single drop of perfume diffused through the volume of six rooms; for taste, a teaspoon of sugar dissolved in two gallons of water.

What is the Just Noticeable Difference (JND), and what does Weber’s Law state about it?

The JND is the minimal change in a stimulus that can be reliably detected. Weber’s Law states that for every sense domain, the change required for a just noticeable difference is a constant proportion regardless of variations in intensity.

According to Signal Detection Theory (SDT), what two factors determine an observer's response to a stimulus?

The person's sensitivity to the stimulus in the presence of noise and their internal decision criterion.

In Signal Detection Theory, what explains why two observers with identical sensory sensitivity might produce different detection rates?

Differences in their internal decision criteria: a more liberal responder with a lower criterion will report detection more often than a conservative responder with a higher criterion.

Which psychological dimensions correspond to the physical properties of light wave length, amplitude, and purity?

Length corresponds to hue (perceived colour), amplitude corresponds to brightness, and purity corresponds to saturation (richness of colour).

How does accommodation maintain a clear retinal image for objects at varying distances?

Muscles change the shape of the eye's lens, making it flatter to focus on far objects and rounder to focus on nearby objects.

How do myopia and hyperopia differ in terms of image focus and eyeball shape?

In myopia (nearsightedness), images focus in front of the retina because the eyeball is too long; in hyperopia (farsightedness), images focus behind the retina because the eyeball is too short.

What are the structural and functional differences between rods and cones?

The retina contains about $120\text{ million}$ rods (active in low light for night vision, absent in the fovea) and about $6\text{ million}$ cones (densely packed in the fovea, active in daylight for colour detection and fine detail).

What is the fovea, and what photoreceptor distribution characterizes it?

The fovea is the region of the retina where visual acuity is clearest; it contains approximately $6\text{ million}$ densely packed cones and zero rods.

How do visual signals flow through the cellular layers of the retina to leave the eye?

Signals pass from photoreceptor cells (rods and cones) to bipolar cells, then to retinal ganglion cells (RGCs), whose $1.5\text{ million}$ axons bundle to form the optic nerve.

What causes the anatomical blind spot in the visual field?

The point where the optic nerve exits the eyeball through a hole in the retina that completely lacks photoreceptor cells.

What subcortical and cortical pathways carry visual signals from the optic nerve into the brain?

Signals pass through the lateral geniculate nucleus (LGN) located in the thalamus and continue to Area V1 (primary visual cortex) in the occipital lobe.

What is Trichromatic Colour Representation?

The pattern of responding across three distinct cone types—S-cones (short/blue), M-cones (medium/green), and L-cones (long/red)—that provides a unique neural code for each perceptible colour.

How does the colour-opponent system account for negative colour afterimages?

Visual neurons operate in opposing pairs (such as red-sensitive L-cones vs. green-sensitive M-cones). Prolonged viewing of red fatigues L-cones; when subsequently viewing a neutral white or grey surface, the unfatigued M-cones respond more strongly, producing a green afterimage.

What are feature detectors in Area V1 specialized to detect?

Neurons in Area V1 have receptive fields tuned to respond specifically to edges and bars at particular spatial orientations.

What are the anatomical routes and primary functions of the ventral and dorsal visual streams?

The ventral stream ("what" pathway) travels from the occipital lobe into the lower temporal lobe to identify object shape; the dorsal stream ("where" or "how" pathway) travels to the parietal lobe to identify object location and guide action.

What dissociation between visual perception and action was demonstrated by Patient D.F. following temporal lobe damage?

Patient D.F. could not consciously match the orientation of a handheld card to a slot (impaired ventral/perception pathway), but could accurately orient and insert ("mail") the card into the slot (intact dorsal/action pathway).

What is the binding problem in visual processing, and what neural mechanism helps resolve it?

The question of how the brain links separate features (such as orientation, shape, and colour) into unified objects. It is addressed through parallel processing and binding neurons in the ventral stream that receive simultaneous inputs representing different features.

Which six Gestalt principles of perceptual grouping are represented in this figure?

(a) Simplicity, (b) Closure, (c) Continuity, (d) Similarity, (e) Proximity, and (f) Common fate.

What classic reversible figure–ground illusion is shown here?

Rubin's Vase, which illustrates how ambiguous edges allow perceptual switching between a central figure (a vase) and its ground (two facing profiles).

What are five monocular depth cues used by the visual system?

Familiar size, linear perspective, texture gradient, interposition, and relative height.

How does binocular disparity generate depth perception?

Because the eyes are horizontally separated, the retinal image of an object falls on a slightly different position in each retina; the brain uses this positional difference (disparity) to calculate distance and depth.

What visual principle produces the dramatic size illusion depicted in the Ames Room?

Forced perspective illusions: when two objects project the same retinal image size, the object perceived as being farther away is interpreted as physically larger.

Which brain region is specialized for visual motion perception, and how does the brain adjust for self-movement?

Area MT in the dorsal stream (temporal lobe); the visual system subtracts intentional movements of the observer's own eyes, head, and body from changes in the retinal image.

How do the waterfall illusion and apparent motion demonstrate motion perception?

The waterfall illusion is a motion aftereffect driven by opponent-process neurons after prolonged viewing of directional motion; apparent motion is the perception of movement resulting from stationary lights flashing in rapid succession at different locations.

How do vision and audition differ in terms of their primary acuity strengths?

The visual system has superior spatial acuity (resolving stimuli close together in space), whereas the auditory system has superior temporal acuity (resolving stimuli close together in time).

What is the difference between change blindness and inattentional blindness?

Change blindness is the failure to detect differences in similar scenes presented consecutively, whereas inattentional blindness is the complete failure to perceive fully visible objects because attention is focused elsewhere.

Which perceptual auditory dimensions correspond to the physical properties of sound frequency, amplitude, and complexity?

Frequency corresponds to pitch, amplitude corresponds to loudness, and complexity corresponds to timbre.

What anatomical structures comprise the outer, middle, and inner ear?

Outer ear: pinna, auditory canal, and eardrum; Middle ear: ossicles and oval window; Inner ear: cochlea and basilar membrane.

How does auditory transduction occur within the inner ear?

Vibrations from the ossicles cause fluid inside the cochlea to move, undulating the basilar membrane in a traveling wave and bending inner hair cells, which generates action potentials along auditory nerve axons.

How do place code and temporal code explain pitch perception?

Place code states that different sound frequencies vibrate specific regions of the basilar membrane (high frequencies at the base, low frequencies at the apex); temporal code registers lower frequencies through the synchronous firing rate of auditory nerve axons.

What is Area A1, and how is it organized?

Area A1 is the primary auditory cortex located in the temporal lobe; it is tonotopically organized, mapping frequencies along a gradient from low to high.

What is the difference between conductive hearing loss and sensorineural hearing loss?

Conductive hearing loss results from mechanical damage to the eardrum or ossicles (often treatable by surgery or hearing aids); sensorineural hearing loss results from damage to the cochlea, hair cells, or auditory nerve (common with aging and treated with cochlear implants).

What are three key principles governing the somatosensory cortex's representation of the body?

Contralateral representation (left body mapped to right hemisphere and vice versa), cortical magnification (more cortex dedicated to areas with high tactile acuity), and distinct "what" (object properties) and "where" (body location) pathways.

What does the two-point discrimination threshold measure, and where is it smallest?

It measures the minimum distance required between two contact points to perceive them as separate; it is smallest (highest acuity) on the fingertips and lips, and largest on the back and calf.

What does the somatosensory homunculus demonstrate about cortical organization?

It illustrates the relative amount of somatosensory cortex devoted to different body parts; regions with high sensitivity and low two-point thresholds (like the hands, lips, and tongue) occupy disproportionately large areas of the brain map.

What are the roles of A-delta fibres versus C fibres in transmitting pain?

A-delta fibres transmit rapid, initial sharp pain, whereas C fibres transmit slower, prolonged dull or aching pain.

What are the two anatomical pain pathways in the brain?

The first sends sensory/discriminative information to the somatosensory cortex to identify where pain is located and its quality; the second sends motivational/emotional signals to the hypothalamus, amygdala, and frontal lobe to drive escape or relief behaviors.

How does the gate-control theory explain pain modulation?

Signals arriving from pain receptors can be inhibited or "gated" by interneurons in the spinal cord through competing feedback from tactile skin receptors (e.g., rubbing an injury) or descending signals from the brain.

What sensory systems are responsible for proprioception and vestibular balance?

Proprioception uses receptors in muscles, tendons, and joints to sense limb and body position; the vestibular system uses three fluid-filled semicircular canals and adjacent organs in the inner ear to detect head motion and maintain balance.

How do Olfactory Receptor Neurons (ORNs) initiate the sense of smell?

Odourant molecules bind to receptor sites on approximately $10\text{ million}$ ORNs (across roughly $350$ receptor types) via a lock-and-key mechanism, transmitting unique combinatorial patterns of action potentials to the olfactory bulb.

Why does smell have such a direct connection to memory and emotional responses?

Olfactory bulb axons bypass initial relays in the thalamus, projecting directly to the frontal lobe, amygdala, and hippocampus, which are central to emotion, memory, and social behavior.

What are the basic taste receptor types, and where are they located?

The five primary taste sensations are salt, sour, bitter, sweet, and umami (with fat/oleogustus as a potential sixth). Receptors are housed in $5,000\text{ to }10,000$ taste buds distributed across papillae on the tongue, palate, and upper throat.

How do tasters, nontasters, and supertasters differ in population distribution and bitter perception?

Tasters ($50\%$ of the population) experience mild bitterness from substances like caffeine and green vegetables; nontasters ($25\%$) perceive no bitterness; supertasters ($25\%$) experience extreme bitterness.

What is the difference between taste and flavour?

Taste is produced strictly by chemical stimulation of taste receptor cells in the mouth, whereas flavour is a multisensory perceptual experience combining taste, smell (olfaction), mouthfeel/texture, and visual cues.