Untitled Quiz

Psychology: Sensation and Perception

• Psychology is the scientific study of mental processes and behaviour.
• Behaviour is the output, while the outside world is the input to the brain (knowledge, memories, etc.).
• Humans, like other animals, have evolved systems for sensing and responding to the environment.
• Psychology also includes sensory modalities like vision, hearing, and other senses.

Lecture Overview

• Part 1: Sensing and the Environment
• Part 2: Vision
• Part 3: Hearing
• Part 4: Other Senses
• Part 5: Perception

Sensation and Perception

• Sensation is the process by which the body gathers environmental information and transmits it to the brain for initial processing.
• Perception is the active process by which the brain selects, organizes, and interprets sensory information.
• Psychological processes are enabled by physical organs such as the brain.
• Systems and mechanisms convert physical stimuli into information understandable by the brain.

Five Basic Senses

• There are five main senses: Vision, Somatosensation (Touch), Audition (Hearing), Gustation (Taste), Olfaction (Smell)
• Each sense modality has specialized receptors for converting physical stimuli into signals.
• These senses are crucial for gathering survival-relevant information.

What Do All the Senses Have in Common?

• All senses use transduction to convert physical stimuli into neural signals.
• All senses have thresholds, including absolute thresholds and just noticeable differences (JNDs).
• Sensory adaptation is a common process of filtering irrelevant information.

Thresholds

• Sensory systems require a minimum amount of energy to be activated (absolute threshold).
• Receptor potentials: Gradual depolarization or hyperpolarization of sensory receptors before and after threshold is reached.
• Average absolute thresholds vary by sense (e.g., hearing, smell, taste, touch, vision).

Sensory Adaptation

• Sensory systems may reduce their response to continuous stimuli.
• This filtering helps concentrate on relevant changes in the environment.

Application: Hearing Tests

• Audiometry tests sound detection thresholds.
• Thresholds vary between individuals and can change over time.

Difference Thresholds

• Difference threshold: minimum difference between two stimuli for a difference to be detected.
• Just Noticeable Difference (JND): Amount of change detectable in different stimuli, varying across stimuli and modalities.

Threshold Laws

• Weber's Law: the size of a JND is a constant proportion of the initial stimulus.
• Fechner's Law: the subjective experience of intensity increases logarithmically as the stimulus intensity increases linearly.
• Steven's Power Law: subjective intensity increases exponentially as actual intensity increases linearly.

Signal Detection Theory (SDT)

• SDT: sensation and perception depends on stimulus characteristics, background stimulation, and the individual.
• Explains why thresholds vary, both across and within individuals.

The Eye

• The eye is the primary visual organ.
• Components include the cornea, pupil, lens, retina, and optic nerve.
• Transduction processes light into neural signals for perception.

The Eye – Blind Spot

• The blind spot is the area where the retina's optic nerve exits the eye, lacking photoreceptors.
• Other information compensates for these gaps.

The Retina

• The retina contains specialized photoreceptors. • Rods: sensitive to low light. • Cones: sensitive to different wavelengths, concentrating in the fovea for detailed vision.

Receptive Fields

• Receptive fields are regions within sensory cells that influence firing rate.
• Convergence and neural interactions form receptive fields across the sensory system.
• Lateral inhibition enhances contrast and sharpens perception.

Neural Pathways

• Impulses sent from the retina to the brain via the optic nerve, following specific pathways.
• Information is processed along “what” and “where” pathways in the brain.

The What and Where Pathways

• "What" pathway identifies objects; "where" pathway localizes objects and guides movement.
• Further processing is done in other parts of the brain.

Perceiving in Colour

• Colour is a psychological property related to wavelengths of light.
• Three dimensions of colour: hue, saturation, and lightness.
• Colour perception is mostly consistent across cultures.

Retinal Transduction of Colour

• Different types of cones in the retina are sensitive to different wavelengths of light.
• Combinations of cone activation create the perception of color.

Theories of Colour Vision

• Young-Helmholtz Trichromatic Theory and Opponent-Process Theory explain colour vision, each accounting for different aspects of color perception.
• Negative afterimages may be explained by opponent-process theory.

Negative Colour Afterimages

• These are a perceptual process following colour stimulation.

Other Senses

• Other senses besides vision and audition include olfactory (smell), gustatory (taste), somatosensory (touch), proprioceptive, and vestibular.
• Each sense modality has specialized receptors and pathways.

Olfaction (Smell)

• Olfactory stimuli are odorants that elicit a chemical response.
• Receptor cells transduce the odor into neural signals for perception.

Gustation (Taste)

• Chemical sense; Tastants binding with receptors in taste cells, causing neural signal transmission.
• There are five basic tastes, but combinations produce more complex sensations.

Somatosensation (Touch)

• A variety of receptors detect touch, pressure, temperature, and pain
• Somatosensory information comes from the body

Nociception (Pain)

• Pain informs of tissue damage or destruction.
• It's a survival mechanism that can be influenced by various factors.

Proprioception

• Refers to sensing the position and movement of the body in space.
• Vestibular sense interprets gravity and movement.
• Kinesthesia interprets movement and position of body parts relative to each other.

Facial expressions and emotions

• Related to the psychological perception and interpretation of an object or stimuli

Perception

• Perception is the interpretation of our sensory experiences.
• Combining sensory data into more meaningful organized patterns creates more profound perceptions.
• Organizing sensory data can create interpretations.

Gestalt Principles

• Our minds group sensations into meaningful patterns using Gestalt principles: figure-ground, proximity, similarity, closure, and good continuation.

Perception Illusions

• Visual illusions emphasize the complex interplay of sensation and interpretation.
• They demonstrate the way we organize and perceive our senses.

Depth or Distance Perception

• Retinal images are two-dimensional, but we perceive the world in three dimensions using visual cues like binocular and monocular clues.

Motion Perception

• Perception of movement occurs when the visual system detects changes in stimulation across the retina.
• Rods respond to motion, or other sensory receptors.

Perceptual Constancy

• Perceptual constancy allows for stable perceptions of objects despite changes in sensory information (such as size, shape, and color).

The Influence of Experience

• Memory and expectation strongly influence how we interpret perceptions.

Top-Down and Bottom-Up Processing

• Top-down processing involves interpreting information based on expectations.
• Bottom-up processing involves interpreting information based on the sensory inputs.