Sensation and Perception Overview

Sensation and Perception

• Stimulus: Any physical energy that produces a response in a sense organ.
• Sensation: The reception of physical energy in the sense organ.
• Perception: Processing, interpretation, and integration of stimuli by sense organs and the brain.
• Stimulus energy is converted into neural impulses by sensory receptors. These impulses travel to specific areas of the brain (visual, auditory, olfactory, etc.).
• Different brain areas handle different senses, and even within a single area (like the visual cortex), different sub-areas specialize.
• Perception requires selection and prioritization of information from the vast amount of sensory input.

Visual Perception

• The human visual system only processes a specific range of wavelengths.
• Retina: A layer of photoreceptor cells in the eye.
• Fovea: A small pit in the retina providing the sharpest vision.
• Cones: Photoreceptors sensitive to color, primarily active in bright light.
• Rods: Photoreceptors sensitive to black and white, primarily active in dim light.
• Color perception depends on the comparison of activity among the three cone types.
• The brain actively processes visual information.

Colour Constancy

• Perceiving objects as having consistent color despite changing lighting conditions. This is not a sensory process but shows cognitive processing.

Gestalt Principles

• Gestalt psychology emphasizes the tendency to perceive organized wholes rather than just individual sensory elements.
• Perception is more than just the sum of its parts.

Depth Perception

• Depth perception involves recovering size and depth from a 2D retinal image. This requires cognitive processing to recover perception from a 2D sensory cue.
• Examples of cues used for depth perception include relative size, light and shadow, interposition (overlap), and texture. Size constancy is another cue related to pre-existing knowledge of the world.

Sensation-Perception-Cognition

• Sensation provides raw sensory information.
• Perception processes that information.
• Cognition further elaborates it.
• Ambiguity and assumptions are inherent at each stage.

Face Perception

• Humans have a strong preference for faces, both human and animal.
• This preference is present from birth.
• Studies (e.g., Valenza et al., 1996; Mondloch et al., 1999) show that infants prefer looking at face-like stimuli. They further show a preference for normal, positive faces as opposed to inverted or negative ones.
• Facial expressions convey emotions, eye contact is critical for communication, and eye direction helps understanding another's attention.
• Studies (Field et al., 1982) indicate that newborns can recognize and imitate facial expressions.
• Expertise with faces is likely due to extensive exposure and importance in our lives.

Face Inversion Effect

• Inverted (upside-down) faces are harder to recognize than upright faces.
• This inversion effect (Yin, 1966) suggests that face processing involves more than just recognition of individual features – the overall arrangement ("configuration") of those features is important too. The Thatcher Illusion (Thompson, 1980) is another example demonstrating this.

Face Recognition Model

• Bruce and Young (1986) proposed a model including stages such as structural encoding (recognizing as a face), face recognition units (FRUs; recognizing it as familiar), personal identity nodes (PINs; identifying the individual), and name generation (retrieving the name).
• Prosopagnosia ("face blindness") is a condition characterized by impaired face recognition.

Embodied Cognition

• Embodied cognition suggests that cognitive systems are fundamentally rooted in sensory and motor systems.
• Representations are distributed across sensory and motor regions.
• Thinking, acting, and interacting with an object activate the same brain regions.
• Cognition is akin to mental simulation, encompassing our perceptual and motor experience.

Body-Mind and Mind-Body Effects

• Studies like Witt & Brockmore (2012) and Tucker & Ellis (2004) show how our bodies can influence perception (body-mind) and vice versa (mind-body).
• Activating motor aspects of an object activates related memories, or activating perceptual aspects activates related motor actions.

Action Observation

• Studies (e.g., Helbig et al., 2010) demonstrate that observing actions primes related perceptual information about the objects involved.

• This supports the idea that cognition is closely tied to our sensory and motor experiences.