Module 7: Sensation and Perception

Understanding How We Experience the World

Every second of every day our brains are receiving an incredible amount of information from the world around us. From the colours we see and the sounds we hear, to the smells, textures and tastes we experience, our senses constantly gather information that our brain must interpret. This process is known as sensation and perception.

In this module I explored how sensory information travels from the environment, through our nervous system and brain, before becoming the meaningful experiences that shape how we understand and interact with the world. I also learned that perception is not always an accurate reflection of reality, but is influenced by our experiences, expectations, emotions and biological processes.

---

What is Perception?

Perception is the process of organising and interpreting information gathered through our senses so that we can understand our environment and respond appropriately.

Rather than simply detecting sights, sounds or smells, perception allows us to recognise objects, identify danger, understand speech, remember faces and navigate everyday life.

The perceptual process follows several stages:

• Environmental stimulus
• Detection by sensory receptors
• Transduction (conversion into electrical signals)
• Neural processing
• Recognition
• Action or response

Without this process our senses would simply collect meaningless information.

---

Bottom Up and Top Down Processing

One of the most interesting concepts in this module was learning that perception works in two different ways.

Bottom Up Processing

Bottom up processing begins with the sensory information itself.

The brain builds an understanding starting with the information received by the sensory receptors before gradually recognising what the object or event is.

This approach is data driven.

Top Down Processing

Top down processing works in the opposite direction.

The brain uses previous knowledge, memories, expectations and experiences to interpret incoming sensory information.

This explains why two people can experience the same situation but interpret it differently.

In reality, our perception usually combines both bottom up and top down processing.

---

Levels of Perceptual Analysis

The module introduced two ways psychologists study perception.

Psychophysical Level

This examines the relationship between environmental stimuli and what we consciously perceive.

It focuses on questions such as:

• Can a person detect the stimulus?
• How strong does it need to be?
• How accurately can it be identified?

Physiological Level

This examines what happens inside the nervous system and brain during perception.

Researchers investigate how electrical activity in neurons and different brain regions relates to perception.

---

The Psychophysical Approach

The psychophysical approach studies the relationship between physical stimuli and human perception.

Researchers measure several different aspects of perception including:

Description

Describing what we see or hear.

Recognition

Correctly identifying an object or stimulus.

Detection

Determining whether a stimulus is present.

This includes:

• Absolute Threshold, the minimum intensity needed to detect a stimulus.
• Subjective Threshold, the point where the stimulus can be identified.
• Differential Threshold (Just Noticeable Difference), the smallest difference between two stimuli that can be detected.

Magnitude Estimation

Estimating how intense or strong a stimulus appears.

Searching

Finding a particular stimulus among many others, such as locating a friend in a crowded room.

---

The Physiological Approach

The physiological approach focuses on how the nervous system and brain create perception.

Key concepts include:

Neurons

Neurons are specialised nerve cells that transmit electrical signals throughout the nervous system.

Each neuron contains:

• Cell body
• Dendrites
• Axon

Resting Potential

The resting electrical state of a neuron before it becomes active.

Action Potential

The rapid electrical impulse that travels along a neuron allowing information to be transmitted.

Synapses

The tiny gaps between neurons where neurotransmitters carry messages from one neuron to another.

Neurotransmitters may either excite or inhibit the next neuron, influencing how information is processed.

---

The Brain and Perception

The cerebral cortex plays a central role in perception.

It processes sensory information while also supporting higher cognitive functions including:

• Memory
• Thinking
• Decision making
• Interpretation

Perception therefore depends on both incoming sensory information and the brain's existing knowledge.

---

Factors That Affect Perception

Perception is influenced by far more than the physical stimulus itself.

Several cognitive factors shape what we notice and how we interpret it.

Attention

Because our brains cannot process every piece of information simultaneously, attention selects what receives conscious awareness.

Anne Treisman's Attenuation Theory suggests that unattended information is not completely ignored but reduced in importance, allowing significant information, such as hearing our own name in a crowded room, to still capture our attention.

Constancy

Our brain perceives objects as remaining stable even when sensory information changes.

For example, a door that is slightly open is still recognised as rectangular despite the changing retinal image.

Motivation

Our needs influence what we notice.

Someone who is hungry is more likely to notice food related stimuli than someone who has recently eaten.

Organisation

The brain naturally organises separate pieces of sensory information into meaningful wholes.

Attitude

Our beliefs and expectations influence how we interpret situations and other people.

Different attitudes can cause two individuals to perceive the same event differently.

Learning

Learning changes perception by providing new knowledge and experiences that influence future interpretation.

---

Distortions of Perception

Perception is not always accurate.

Hallucinations

Hallucinations occur when a person experiences perceptions without an external stimulus.

They may result from:

• Certain drugs
• Sleep deprivation
• Sensory deprivation
• Extreme stress
• Psychotic disorders

Illusions

Illusions occur when a real external stimulus is interpreted incorrectly.

These demonstrate that perception depends on brain processing rather than simply receiving sensory information.

---

Key Learning Points

• Perception is the process of interpreting sensory information.
• Sensation gathers information, while perception gives it meaning.
• Bottom up processing relies on sensory input, whereas top down processing uses prior knowledge and experience.
• Psychophysical psychology measures the relationship between physical stimuli and perception.
• Physiological psychology examines how the brain and nervous system create perception.
• Neurons communicate through electrical signals and neurotransmitters.
• The cerebral cortex is essential for interpreting sensory information.
• Attention, motivation, learning, attitudes and expectations all influence perception.
• Hallucinations and illusions demonstrate that perception is not always an accurate reflection of reality.
• Human perception is an active process that combines sensory input with previous knowledge and cognitive processes.

---

Final Reflection

This module has shown me that perception is much more complex than simply seeing or hearing something. Our brains actively construct our experience of reality by combining information from our senses with memories, expectations, emotions and prior knowledge. Understanding how perception works helps explain why people can experience the same event differently and highlights the remarkable complexity of the human brain. It has also reinforced the importance of considering both biological processes and psychological influences when studying human behaviour.