Consumer Behaviour & Buying Decision Process

Understanding why and how consumers buy is central to marketing strategy.

Kotler's Buying Decision Process (5 stages):

1. Need Recognition: Triggered by internal stimulus (hunger, thirst) or external stimulus (advertisement, word of mouth). Example: a Doordarshan ad for Colgate triggers the realisation that one's toothpaste is running low.
2. Information Search: Internal (memory) and external (friends, reviews, Google). The consideration set shrinks to 3–5 brands during search.
3. Evaluation of Alternatives: Consumers weigh attributes by importance. Multi-attribute model (Fishbein): overall attitude = Σ (importance × belief rating for each attribute).
4. Purchase Decision: Final choice, but can be disrupted by negative word of mouth or stock-out at point of purchase.
5. Post-Purchase Behaviour: Compare expectations vs. reality. Dissatisfied customers: voice (complain), exit (switch brand), loyalty (stay reluctantly). Net Promoter Score (NPS) = % Promoters − % Detractors — a widely used loyalty metric (Bain & Co., 2003).

Cognitive Dissonance: Post-purchase doubt ("Did I make the right choice?"). Marketers reduce it through reassuring after-sale communications, warranty cards, and follow-up calls.

Impulse buying accounts for 40–80% of all purchases in some categories (candy, magazines at checkout). Nudge Theory (Thaler & Sunstein, 2008 Nobel Economics Prize concept) is used in store layouts, default options in e-commerce to increase conversions.

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