During the First World War, British and US ships were painted in high contrast “dazzle” patterns, which were believed to confuse submariners aiming torpedoes at them by distorting the perception of the vessel’s heading .

But new research suggests the strategy may have only provided protection for fast moving, distant ships. It appears this week in the journal Royal Society Open Science.

“We investigated the effects of different camouflage patterns, including versions used in the war, on the perceived direction of travel for a 3-dimensional computer model of the RMS Mauretania,” the authors of the paper write.

The RMS Mauretania was used as a troop ship during WWI.

The 16 participants in the study viewed the simulated ship through a periscope-like window replicating real conditions, such as distance and periscope height. The digitised ships appeared pointed in a randomised direction and were coloured either a neutral grey or 1 of 5 different camouflage patterns.

“We found both benefits and problems associated with the dazzle approach,” the authors write, “particularly due to the interactive effects of hysteresis and twist.”

They found dazzle camouflage patterns that incorporated texture gradients “twisted” the perceived direction of the ship. However, another “hysteresis” effect made it look like ships were moving across the horizon rather than towards or away from the viewer, regardless of dazzle camouflage.

Interestingly, this hysteresis effect decreased as participants’ years of sailing experience increased. Though the reason for this remains unclear.

“We cannot know whether subtle visual cues were more readily available to experienced participants compared to others, or whether they simply put more effort into giving precise responses,” the authors write.

In separate torpedo aiming computer simulations the researchers showed that, depending on the heading of the ship, the effects of twist and hysteresis combined to either enhance or diminish their protection from accurate torpedo aiming.

“Our work suggests that many WWI dazzle patterns would have been of limited benefit in systematically deceiving the enemy about a target ship’s direction,” the authors conclude.

“Indeed, our application of [the] pattern for RMS Mauretania produced only 1° more twist than the neutral grey condition.”

Instead, the camouflage that provided the most twist was that of regular circles increasing in size in a gradient across the length of the ship.

“If fast ships were painted with camouflage that introduced a strong twist, it might have introduced targeting errors for experienced submariners which could have saved lives.”