The peak-end rule

Imagine Sarah, exhausted after hours of intense labor and seemingly never-ending contractions, experiencing waves of overwhelming pain. Yet, as she cradles her newborn baby, crying for the first time, all of the pain suddenly seems distant and insignificant. The joyful rush of holding her child creates a powerful, positive memory that overrides the intense discomfort she endured. This beautiful ending transforms her recollection of childbirth, allowing her to recall it as an incredibly positive experience despite its undeniable hardships.

Now, picture Alex, reflecting on a relationship that lasted several happy years filled with laughter, comfort, and mutual support. Yet, when the relationship ends abruptly in a painful breakup, Alex finds his memories tainted. Despite all the wonderful moments they shared, the intense emotions from their final arguments overshadow his past happiness. Whenever Alex thinks back on this relationship, it’s the sting of heartbreak and the harsh words exchanged at the end that dominate his memory. This overriding memory illustrates how a negative conclusion can dramatically alter the perception of an overall positive experience.²⁵

Both of these examples demonstrate that no one remembers every single moment of their life. When recalling memories, individuals are usually shocked when they understand how biased their memory of an event is. The peak-end rule influences our evaluations of experiences and can impact human behavior, decision making, and perceptions in both positive and negative ways.

But how does our brain decide which memories to keep and which to let fade away?

The peak-end rule is a specific manifestation of the snapshot model.  This framework, originally proposed by Daniel Kahnemann and Barbara Fredrickson, suggests that we remember events using a representational heuristic, where specific moments—akin to snapshots from a vacation—shape our overall perception and assign meaning to the experience.¹³ However, unlike the curated vacation photos on our smartphones, these defining moments are distinguished by their intensity rather than by being inherently positive or negative.

In the specific case of the peak-end rule, the snapshots we remember are more specific. We tend to recall an event based primarily on its most emotionally intense moments (both good and bad) and how it ends, rather than the entire experience as a whole. However, as the negativity bias tells us, we tend to remember negative experiences more vividly than positive ones.¹⁹