The closer you get, the harder you push. Always.
Motivation to complete a goal increases. As people approach completion. Effort and engagement accelerating proportionally. To perceived proximity. To goal achievement.
Hull's original behavioral research (1932) demonstrated the pattern. Rats ran faster approaching food rewards. Speed increasing systematically. As they neared goals. Establishing that proximity drives motivation enhancement.
Kivetz, Urminsky, and Zheng's modern research (2006) validated persistence. This effect persists in human behavior. Coffee shop loyalty card holders accelerated purchases. As they approached reward thresholds. Visit frequency increasing 20%. Between first and last stamps required for free coffee.
The principle: Show progress. Proximity motivates. Harness acceleration.
Hull's pioneering experiments (1932) observed rats learning to navigate mazes toward food rewards. Through systematic measurement, he documented that rats accelerated as they approached goals—running faster in maze sections near food than distant sections despite identical physical effort requirements. This acceleration pattern emerged reliably across different rats and maze configurations, establishing goal proximity as fundamental motivational variable. Hull formulated this observation as the goal-gradient hypothesis: the tendency to approach a goal increases with proximity to that goal, creating predictable behavioral intensification as organisms near objectives.
Hull's Principles of Behavior (1943) positioned the goal-gradient within comprehensive learning theory explaining how reinforcement strengthens behavior. His mathematical formalization demonstrated that response strength increases as a function of decreased distance to reinforcement, providing quantitative framework for predicting motivation levels based on goal proximity. This theoretical foundation explained why partially completed tasks feel more compelling than not-yet-started tasks—psychological distance to completion serves as primary motivational driver regardless of absolute effort invested.
Kivetz, Urminsky, and Zheng's landmark study (2006) resurrected Hull's hypothesis demonstrating its continued relevance in modern consumer behavior contexts. Their coffee shop loyalty card experiment revealed customers receiving 12-stamp cards (requiring 10 purchases, 2 pre-stamped) completed programs significantly faster than customers receiving 10-stamp cards (requiring identical 10 purchases, none pre-stamped). The artificial endowment of two "free" stamps created illusory progress making goals feel closer despite equivalent actual requirements. This demonstrated that perceived proximity—not just actual progress—drives goal-gradient effects, validating strategic use of artificial progress in interface design.
Their research documented purchase acceleration patterns—coffee buyers increased visit frequency as they approached reward thresholds, with average time between purchases decreasing from 2.9 days (between stamps 1-2) to 2.0 days (between stamps 9-10). This 31% acceleration occurred despite identical reward (free coffee) and remaining effort (one purchase) throughout program. The systematic acceleration pattern confirms goal-gradient operates continuously rather than threshold effects activating only near completion.