Effective as the spoon is, the reason for its effectiveness is uncertain. The lure doesn't resemble a bait fish as some artificial lures do. However, being shiny, the reflections may imitate those from a floundering bait fish. An injured baitfish is an invitation to a strike by any predator seeking a meal. Because spoons are designed to wobble or revolve, their effectiveness depends upon the speed of their gyrations.
Different shapes cause various spoons to react differently at various speeds.
To use them properly, you have to control their actions by the speed of your trolling. When first using a spoon, test it at various speeds in the water to determine at which it functions best. Some demand extremely high speeds. Others perform best at slow ones. The individual design is a big factor in this variation.