MKTG2112 · Consumer Behaviour
Perception & Sensory Marketing: JND, Weber's Law, Gestalt & Semiotics
Perception, not objective reality, drives behaviour — and this final topic explains how stimuli become meaning. It covers sensation vs perception and the five senses, absolute and differential thresholds and the Just Noticeable Difference, Weber's Law (K = ΔI/I), the exposure–attention–interpretation–response pipeline, Gestalt principles of organisation, and semiotics (object/sign/interpretant), plus sensory, experiential and AR marketing. It is examined as short-answer / essay, so you apply JND logic to a pack or price change, or read an ad through Gestalt or semiotics.
What this chapter covers
- 011. Sensation vs perception: sensation is the raw receptor response; perception selects, organises and interprets it
- 022. The five sensory systems: sight, sound, smell, taste, touch (sensory/experiential marketing)
- 033. Absolute threshold (minimum detectable) vs differential threshold (detecting a difference)
- 044. Just Noticeable Difference (JND): the smallest change a consumer can detect
- 055. Weber's Law: K = ΔI/I — the change needed to be noticed is proportional to the original intensity
- 066. Subliminal perception (below conscious awareness — largely ineffective for persuasion)
- 077. Perceptual pipeline: stimuli + individual factors → exposure → attention → interpretation → response
- 088. Gestalt principles (closure, similarity, figure-ground, proximity, continuity) and semiotics (object/sign/interpretant)
JND & Weber's Law applied (short answer, 7 marks)
- 1 markDefine the JND: the minimum change in a stimulus that a consumer can detect (the differential threshold).
- 2 marksState Weber's Law: K = ΔI/I — the change ΔI needed to be noticed is proportional to the original intensity I (K is the Weber constant for that sense/dimension).
- 2 marksPack shrink: keep the size reduction below the JND (a small percentage off a relatively large pack) so the change isn't perceived, protecting loyalists.
- 2 marksPrice cut: make the reduction exceed the JND (a large, salient percentage drop) so the improvement is clearly noticed and drives a response.
Key terms
- Sensation vs perception
- Sensation is the immediate response of sensory receptors to basic stimuli (light, sound); perception is the process by which those sensations are selected, organised and interpreted into meaning. Perception, not objective reality, drives behaviour.
- Absolute vs differential threshold
- The absolute threshold is the minimum level of a stimulus that can be detected on a sensory channel; the differential threshold is the ability to detect a difference between two stimuli — the minimum detectable difference being the Just Noticeable Difference.
- Just Noticeable Difference (JND)
- The smallest change in a stimulus a consumer can detect. Marketers stay below the JND to make an unwelcome change (a shrink or price rise) unnoticed, and exceed it to make a welcome change (a discount or upgrade) obvious.
- Weber's Law
- K = ΔI/I — the change in intensity (ΔI) required to be noticed is a constant proportion (K) of the original intensity (I). The bigger the starting stimulus, the bigger the absolute change needed to cross the JND.
- Perceptual pipeline
- The sequence stimuli pass through to become a response: marketing stimuli plus individual factors → exposure (random or deliberate) → attention (selective, limited capacity) → interpretation (meaning via schemas) → behavioural response.
- Gestalt principles & semiotics
- Gestalt principles describe how we organise stimuli into wholes — closure, similarity, figure-ground, proximity, continuity ('the whole is greater than the sum of its parts'). Semiotics studies signs and meaning via the object (product), sign (sensory imagery) and interpretant (intended meaning).
Perception & Sensory Marketing: JND, Weber's Law, Gestalt & Semiotics FAQ
Why does the unit say perception, not reality, drives behaviour?
Because consumers act on the meaning they construct, not on objective stimuli. Two people exposed to the same ad attend to different parts, interpret it through different schemas, and respond differently. Sensation gives raw input, but the selecting–organising–interpreting of perception is where behaviour is decided — which is why marketers manage exposure, attention and interpretation, not just the stimulus.
How do I apply Weber's Law in an exam answer?
State K = ΔI/I, explain that the noticeable change scales with the starting intensity, then apply the strategic rule: to hide a negative change (shrinking a pack, raising a price) keep it below the JND; to make a positive change land (a discount, a quality upgrade) make it exceed the JND. The key insight is proportionality — a 5% change off a large base is harder to notice than the same absolute change off a small base.
What's the difference between Gestalt principles and semiotics?
Gestalt principles explain how the mind organises raw visual elements into a coherent whole — closure (filling gaps), similarity, figure-ground, proximity and continuity — useful for analysing logos and layouts. Semiotics explains how meaning is carried by signs, through the object (the product), the sign (the sensory imagery used) and the interpretant (the intended meaning). One is about organising perception; the other is about decoding meaning.
How is this topic examined?
As short-answer / essay: define and apply the JND and Weber's Law to a pack/price change, trace the perceptual pipeline for an ad, identify Gestalt principles in a design, or decode an ad with the semiotic triangle. The JND/Weber application is a near-certain favourite, and the absolute-vs-differential-threshold distinction is a common MCQ trap.
Exam move
Lead with the two quasi-formulas: be able to define the JND and write Weber's Law as K = ΔI/I, and rehearse the 'below to hide, above to highlight' application until it's instant. Learn the threshold vocabulary cleanly (absolute = detect at all; differential = detect a difference = JND) because it's a common trap. Memorise the perceptual pipeline as an ordered flow and the five Gestalt principles with a quick visual example each, and keep the semiotic triangle (object/sign/interpretant) ready to decode an ad. In the exam, name the principle or law and apply it to a concrete stimulus, finishing with the marketing implication.
