According to attentional control theory (ACT; Eysenck et al. in Emotion 7(2):336–353, 2007) anxious individuals recruit motivation on demanding tasks, which helps prevent performance shortfalls. We used a quasi-experimental design to examine the relationship between trait anxiety (operationalised using questionnaire scores), situational stress (manipulated using ego threat instructions) and motivation (indexed using a self-report goal-commitment scale) in predicting effectiveness (accuracy) and efficiency (accuracy divided by RT) on the reading span task. After controlling for depression, the variables were not related to effectiveness; however there was a significant trait anxiety × goal-commitment interaction on reading span efficiency. Higher trait anxiety predicted better efficiency at higher goal-commitment, and poorer efficiency at lower goal-commitment, and these relationships were independent of situational stress. Results are interpreted in terms of ACT.