This study examines the Theta/Beta Ratio (TBR) in EEG measurements to infer the cognitive load during decision-making across different attachment styles. Participants’ EEGs were analyzed within the secretary problem framework while they were at rest and making decisions. The secure attachment group demonstrated higher TBR difference medians, suggesting a lower cognitive load. Conversely, the fearfully avoidant group exhibited significantly lower medians, indicating a heightened cognitive load. The anxiously attached group’s TBR varied widely, suggesting inconsistent cognitive engagement, while the avoidant group’s levels were moderate. These results imply that attachment style determines the cognitive load experienced during decision-making, with fearfully avoidant individuals bearing the highest load. This research elucidates the neurobiological links between attachment styles and cognitive processing.