What is the fundamental difference between sensation and perception?

Sensation is the biological process of detecting physical stimuli through sensory receptors, whereas perception is the psychological process of organizing and interpreting that sensory information to give it meaning.

How does bottom-up processing differ from top-down processing?

Bottom-up processing starts with the raw sensory data and builds up to a complete perception (data-driven), while top-down processing uses pre-existing knowledge, expectations, and context to interpret incoming data (concept-driven).

When would a person rely more heavily on bottom-up processing than top-down processing?

A person relies on bottom-up processing when encountering a completely new or ambiguous stimulus for which they have no prior experience or mental framework to guide their interpretation.

What is a common mistake when identifying sensory adaptation?

A common error is confusing it with a conscious choice to ignore something. Sensory adaptation is an involuntary physiological reduction in receptor sensitivity due to constant, unchanging stimulation.

Why is it incorrect to say that we 'see' with our eyes?

Biologically, our eyes only perform sensation (detecting light). We actually 'see' with our brain, which performs the perception (interpreting the neural signals sent from the eyes).

What error occurs if one assumes the absolute threshold is a fixed, unchanging number for everyone?

The absolute threshold is not absolute; it is defined as the point of detection 50% of the time and can vary based on a person's psychological state, fatigue, and motivation (Signal Detection Theory).

Define 'Transduction' in the context of sensory systems.

Transduction is the process of converting physical energy, such as light waves or sound vibrations, into electrical neural impulses that the brain can process.

What is the 'Absolute Threshold'?

The absolute threshold is the minimum intensity of a stimulus required for a person to detect its presence at least 50 percent of the time.

State Weber's Law regarding the difference threshold.

Weber's Law states that for an average person to perceive a difference between two stimuli, they must differ by a constant minimum percentage (a ratio) rather than a constant fixed amount.

What is a 'Perceptual Set'?

A perceptual set is a mental predisposition or readiness to perceive one thing and not another, usually driven by top-down factors like expectations, culture, or emotions.

The Difference Between Sensation & Perception | AQA GCSE Psychology

The Difference Between Sensation & Perception

Summary

Sensation and perception are two distinct yet inseparable stages of processing environmental information. Sensation involves the biological detection of physical stimuli by sensory receptors, while perception is the psychological process of organizing and interpreting that data to create meaningful experiences.

1. Definition & Core Concepts

Sensation is the initial process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment. It is the purely biological phase where physical energy (like light or sound) is captured by specialized cells.
Perception is the subsequent cognitive process of organizing and interpreting sensory information. It allows us to recognize meaningful objects and events, transforming raw data into a coherent mental representation of the world.
While sensation provides the 'raw materials' of experience, perception provides the 'finished product' or the meaning behind those materials.

A flowchart showing the progression from physical stimulus to sensation, then transduction, and finally perception in the brain.

2. Underlying Principles: Processing Directions

Bottom-up processing is analysis that begins with the sensory receptors and works up to the brain's integration of sensory information. It is data-driven, meaning the perception is constructed entirely from the incoming stimulus features.
Top-down processing is information processing guided by higher-level mental processes, such as experience and expectations. It is concept-driven, where our brains use what we already know to fill in gaps or interpret ambiguous sensations.
Most everyday experiences involve a combination of both; bottom-up processing detects the lines and colors of a face, while top-down processing recognizes that face as a friend.

3. The Process of Transduction

Transduction is the critical conversion of one form of energy into another. In the context of sensation, it refers to the transformation of stimulus energies (like light waves or chemical molecules) into neural impulses.
This process occurs at the level of the sensory receptors, which act as biological transducers. Without transduction, the brain would have no way to 'read' or understand the physical world.
Once transduction is complete, the resulting electrical signals travel via specialized neural pathways to specific regions of the brain for perceptual analysis.

4. Key Distinctions

5. Thresholds & Adaptation

6. Exam Strategy & Tips