By Pete Dyson, Senior Behavioural Strategist at Ogilvy Consulting's Behaviour Change Practice

Do Replays Make Juries and Referees Harsher?

You’d think that a slow motion replay improves decision making; giving the eye a chance to see more of what’s going on, spotting motion that’s otherwise missed, identifying precisely when an action started and whether or not contact was made.

It turns out it does all this, but at a cost.

A study published last August in the Proceedings of the National Academy of Sciences USA suggests that slow motion leads a courtroom jury to perceive the people involved were acting with greater intent.

An experiment recruited subjects to be jurors and watch a video of a convenience store robbery and shooting, either in slow motion or in real time. Those who watched the slow-motion video reported thinking the robber had more time to act and was acting with greater intent. The effect persisted even when the researchers displayed a timer on the screen to emphasize exactly how much time was passing. Even when juries saw both the slow and the regular speed CCTV they were still 50% more likely to agree the first degree murder verdict than those that just saw the normal speed.

The study’s author Prof Caruso explains that showing both normal and slow motion “doesn’t actually eliminate the subjective feeling or the sense that he really had a lot of time, and those feelings of the amount of time he had to act are really predictive of their intentionality judgments.”

The sporting world is now embracing slow motion replays, including the new VAR system used in the 2018 World Cup.

In 2017 the an experiment showed 88 elite football referees from 5 European countries 60 video clips of foul situations from football matches in real time or slow motion.Judgements were validated by two independent ex-international referees.

The researchers found no significant difference in the accuracy of a referee’s decision about if a foul had occurred or not, with slow-motion videos (63% accurate) compared to the real-time videos (61% accurate). However, the judgement of intention or force behind a foul differed. More red cards were given by referees watching in slow motion compared to those watching real time video playbacks.

In all instances, slow motion increases accuracy but at the cost of biasing towards severity. The best explanation is that when we watch footage in slow motion, we cannot help but assume that because we as viewers have more time to think through the events as they unfold, the same holds true for the people in the video. Our eyes never evolved to be objective, they see through memory, context and circumstance.

So what can we do about it?

All studies have concluded that slow motion should be used more cautiously and the referees/jurors be educated on its effects.

We can only expect slow motion to reach further, wider and deeper into our lives.

As more cameras are used, I would like to question the validity of showing events in multiple angles. As the famous Guardian ‘Points of View’ 1986 TV ad showed, perspective is everything; a pedestrian can look like a saviour or a criminal depending on the shot used.

I would advocate for a symbol to be shown in the bottom corner, identifying the video as ‘slow motion’ to improve salience and ensure viewers know their judgement is likely to be shifted.


For more on behavioural science read Sam Tatam's piece on seeing the unseen here.

Jochim Spitz, Koen Put, Johan Wagemans, A. Mark Williams & Werner F. Helsen (2017) Does slow motion impact on the perception of foul play in football?, European Journal of Sport Science, 17:6, 748-756, DOI: 10.1080/17461391.2017.1304580
Caruso, E. M., Burns, Z. C., & Converse, B. A. (2016). Slow motion increases perceived intent. Proceedings of the National Academy of Sciences, 113(33), 9250-9255.