Pain experiments are hampered by serious ethical considerations and the difficulty of recruiting suitable subjects without psychological baggage. Most experiments concern pain thresholds – the measurement of the least noxious stimulus that causes pain. A lesser number of experiments involve measure pain tolerance – the point at which willing volunteers are no longer willing.
Punishments are likely to exceed the pain tolerance, perhaps by an increasing degree with an increasing number of strokes. Under such circumstances, the last strokes may hurt the most. However, the pain intensity eventually plateaus and extra strokes will have little further effect beyond causing further wounding.