Understanding how humans adapt to streaky performance under uncertainty is central to research on belief updating, attention, and decision-making. Professional basketball provides a naturalistic setting in which these processes can be observed under real incentives and time pressure. Using NBA player-tracking data, we examine how defenders adjust their behavior in response to offensive shooting outcomes, shifting focus from shooter performance to defensive adaptation. We conduct three complementary studies relating multiple spatial defensive metrics to recent shooting history, including asymmetric responses to makes versus misses, cumulative success over short memory windows, and escalation during extended streaks. Across analyses, we estimate regression-based models with appropriate clustering and controls to isolate behavioral updating from contextual factors. The results show clear evidence of asymmetric updating: defenders tighten coverage more after made shots than they relax following misses, with effects strongest for the closest defender. Defensive adjustments are driven primarily by short recency windows of approximately three to five shots. Escalation during long hot streaks is limited, with defensive responses stabilizing rather than increasing indefinitely. Together, these findings suggest that defensive behavior reflects psychologically structured but bounded belief updating rather than full rational inference or indiscriminate overreaction to streaks.
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