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Showing posts with label speed. Show all posts
Showing posts with label speed. Show all posts

Monday 6 December 2021

Looks fast, feels faster - why the speed gun is only part of the story

Data on release points and trajectory are helping to break down the mysteries of why some bowlers are harder to face than others writes Cameron Ponsonby in Cricinfo



Shubman Gill ducks a Pat Cummins bouncer during India's Test tour of Australia in 2020-21 AFP/Getty Images
 
 


South Africa's Andrew Hall is on strike against Brett Lee at the Wanderers stadium in Johannesburg. The ball is bowled and Hall tucks it into the leg side before setting off for a gentle single.

As he jogs to the other end he hears a belated cheer from the crowd. Confused, he looks around to see the big screen displaying an announcement. He has just faced the fastest ball ever to have been bowled at the Wanderers.

Still confused, Hall's eyes move from the screen to Lee and they trade a quizzical look: "There's no way that was that quick."

The next ball, Lee runs in and bowls a bouncer to Gary Kirsten that flies past his face. Lee and Hall catch each other's eye once more,

"That one was."

You see, the speed gun is the movie adaptation of your favourite book. Yes, it tells the story. But it doesn't tell the full one.

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"A lot of what makes Test players special happens before the ball comes out of a bowler's hand."

Those are the words of England analyst Nathan Leamon, speaking on Jarrod Kimber's Red Inker podcast. As a starting point, it shines a light on one of the limitations of the speed gun. It only tells us how fast a ball is at the point of release and tells us nothing about what has happened before or what happens after.

And what happens before is crucial. It is very easy to think of facing fast bowling as primarily a reactive skill. In fact, read any article on quick bowling and it will invariably say you only have 0.4 seconds to react to a 90mph delivery.

But what does that mean? No one can compute information in 0.4 seconds. It's beyond our realm of thinking in the same way that looking out of an aeroplane window doesn't give you vertigo because you're simply too high up for your brain to process it.

However, the reason it's possible is because, whilst you may only have 0.4 seconds to react, you have a lot longer than that to plan. And the best in the world plan exceptionally well.

Hall describes a training method that South Africa would use in order to be able to associate a bowler's release point with length. After a ball was bowled, they'd walk down the wicket and place a cone or mark a spot with their bat where they believed the ball had landed. The coach would confirm it or correct what the player thought.

The idea is in essence basic trigonometry. Over time, you learn to associate that if a bowler releases the ball with his arm at 12 o'clock, the delivery would be full. If he releases the ball at 1 o'clock, it would be short. It's a process designed to consciously train the subconscious, and Jacques Kallis was the best at it.

"Whether he played and missed," Hall says, "or left it, or ducked out the way, he'd be able to come down the track and isolate a rough area of where that ball had landed. And the reason he was so good at it is he became really sharp at picking up length and he made some bowlers look slower because of that. Because as they let go of the ball, he knew within a couple of inches where it was going to land."


Jasprit Bumrah roars after having Joe Root caught in the slips AFP/Getty Images



There are a number of pre-delivery cues that Hall, as an international player, would be looking out for. Some were obvious tells, such as a bowler running in that bit harder before bowling a bouncer; others more subtle, like a bowler's head falling away in their action so they were able to push the ball into the batter and bowl an inswinger.

These cues weren't restricted to fast bowlers either. When talking about how to face Muthiah Muralidaran, Hall explains that one of the cues the South Africans would look out for was where his right elbow would be pointing as he entered his delivery stride. If it was pointing out at 90 degrees with his hand by his ear lobe, that was the sign that Muralitharan was going to bowl his off-spinner. If his elbow was pointing down towards the batter, it was probably a doosra coming up.

"You still wouldn't be able to play it half the time," Hall adds, "but you had an idea."

And some bowlers give you more of these cues than others, meaning a bowler at 87mph may feel quicker than one at 90mph if they give the batter fewer clues in their action.

Mark Ramprakash spoke of this when comparing his experience of facing Lee and Jason Gillespie in the 2001 Ashes. Lee was the faster bowler of the two, but his textbook action, with the ball always in sight, meant that Ramprakash felt he could consistently time his pre-delivery movement. But when he faced Gillespie, despite his being slower on the speed gun, it felt quicker. And this was because Gillespie would appear almost to release the ball before he'd really landed on the ground, throwing off Ramprakash's timings. When facing Lee, Ramprakash was planning. But when he was facing Gillespie, he was reacting.

In simple terms, there's a correlation between a bowler being "different" and the feeling that they are faster than they actually are. Batters are brought up on a diet of right-arm-over bowling that is released from nigh-on the same area, ball after ball after ball. Remove that familiarity, and the feeling of speed goes up.

In the Caribbean in 2019, TV showed Jasprit Bumrah's release point was half a metre closer to the batter than Kemar Roach's. This gave Bumrah the effect of bowling 3.7mph faster than the speed gun was showing

"Take Lasith Malinga," Hall says. "If you've not faced him before, you're literally going 'what am I supposed to watch?' But you soon get told, when he gets into his action, to watch the umpire's chest and neck. If you're watching his arm, you're struggling. And that's why in the beginning he'd clean people up and they'd say 'ah, he's quick'. He's not that quick. You just couldn't follow the ball."

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Another quirk of how we consider pace is that by measuring the speed at which a ball is released, we're not actually measuring how long it takes to reach the batter. And there's a difference.

For instance, if you set up a bowling machine at 85mph and deliver three balls in a row, one of which is a full toss, the second a good length delivery and the third a bouncer, each of the three balls will reach the other end in a different amount of time because when the ball hits the pitch, it slows down. And the steeper that impact is, the more it will slow. So counterintuitively, the bouncer, cricket's scariest delivery, is actually the slowest of the three, whereas the full toss, cricket's worst delivery, is the fastest.

But what we don't know is how different bowlers compare to each other in terms of how much pace they lose off the wicket. The information is out there, but it's just not readily available. Angus Reid from VirtualEye - the company that provides ball-tracking data for Test matches in Australia - recalls how, during Naseem Shah's Test debut for Pakistan, they did a piece for broadcast comparing how he and Australia's Pat Cummins were releasing the ball at very similar speeds, but Shah was reaching the batter faster due to a combination of his height, ball trajectory and "skiddy" nature.


Steven Smith was pinned by a Jofra Archer bouncer at Lord's in 2019 Getty Images


And we know from player anecdotes that these things matter. Hall explains how bowlers will sometimes bowl their bouncer with a cross-seam in the hope that the ball lands on the lacquer and loses less pace when it pitches. It is the same notion that Joe Root expressed earlier this year when he said India's spinner Axar Patel was beating England for pace in the pink-ball Test at Ahmedabad, because the skid off the lacquer gave the feeling that the ball was "gathering pace" off the wicket.

Conversely, many bowlers are said to bowl a "heavy ball", whereby batters feel that the ball is "hitting the bat harder" than expected. One such bowler was New Zealand bowler Iain O'Brien, who believes this was a consequence of the ball kicking up off the pitch and striking the blade higher than anticipated, due to more backspin being imparted upon release. Such was the backspin that Andrew Flintoff imparted on the ball, in the lead up to the 2005 Ashes he was accused of chucking as his wrist would snap so dramatically at the point of delivery.

This is one of the difficulties of trying to express the feeling of speed to a wider audience. For the spectator, it's merely a number because we have no other frame of reference. But for the batter, it's an experience. A moment in time that is almost over before it's begun.

One former international cricketer laughed when asked whether he would check the speed gun after facing a delivery. "Why would I need the speed gun to tell me if a ball was fast? I was the one who just faced it."

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The final piece of the puzzle concerns the ball's release point.

When India were touring the Caribbean in 2019, TV showed an overlay of Jasprit Bumrah's release point compared to Kemar Roach's, demonstrating that Bumrah was bowling the ball half a metre closer to the batter than Roach. Some quick maths showed that this gave Bumrah the effect of bowling 3.7mph faster than the speed gun was showing. Cricket has long been played on a pitch that is 22 yards. Bumrah plays on one that is 21.5.

Admittedly, this advantage was spotted because Bumrah is on the extreme, gazillion-jointed end of the scale, enabling him to bowl closer than anyone else in a way that other bowlers can't. But given we pay attention to how wide on the crease a bowler will bowl and also how high a bowler's release point is, surely we should know how close a bowler is bowling to the batter, given it is the single easiest way of apparently increasing pace.

This effect is measured in baseball. In fact, everything is. While cricket shrugs its shoulders and says "I guess we'll never know, folks" for a myriad of data-points, every intangible detail in baseball is known and measured.

How close a pitcher releases the ball to a batter is known as "Extension" and translates to what's known as "Perceived Velocity". Famed pitching coach Tom House believes that, if you can throw the ball one foot closer to the batter, then it equals an extra 3mph for the person at the other end. Tyler Glasnow and Luis Castillo are two pitchers who both throw their fast-ball at 97mph. Glasnow's extension is one of the best in the league and Castillo's is one of the worst. As a result, Glasnow feels like he is throwing at 99mph and Castillo feels like he is throwing at 95mph.Spin rates, which could resolve cricket's heavy-ball phenomenon, are a hugely important measurement in baseball - so much so that they can now be taken into consideration in the selection process.

Even the ultimate intangible, the impact an action has on a batter before the ball has been released, is beginning to be quantified by a biomechanics company known as ProPlayAI, who have started tracking what they call a "deception metric", which measures the amount of time a batter has to see the ball in a pitcher's hand before release.


Mitchell Johnson was ferociously quick during the 2013-14 Ashes Getty Images



The culmination of all these factors comes in the form of a pitcher named Yusemeiro Petit, described by baseball writer Ben Lindbergh as "the poster boy for the power of deception".

Petit's average fast-ball is 87mph. A whole 7mph slower than the rest of the league. He is 37 years old and over 500 games into his career. And he has made it this far, not by being a force of nature but by representing the mystery of it. He is one of those alien fishes at the bottom of the ocean that has lived forever and we don't know why.

In the 2005 edition of the Prospect Handbook, Baseball America, which is the sport's annual guide on the young players to look out for, Petit was described as leaving "batters and scouts scratching their heads ... Nothing about it [his fast-ball] appears to be exceptional - except how hitters never seem to get a good swing against it."

Fast forward to the present day and the reasons for Petit's success are beginning to be decoded. Simply put, Lindbergh describes him as a "hider and a strider". Throwing the ball far closer to home plate than would be expected and giving the batter little to no sight of the ball in the process. The result of which is a pitcher who is far quicker than the speed gun would lead you to believe.

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All of this isn't to say that the speed gun is useless. It isn't. But it represents different things to different people. As a broadcasting tool, it's an excellent way of telling a story in a bite-size chunk. And for a bowler, it represents the result of their process. Get everything right and watch that number go up.

For batters, however, it represents part of the process that leads to their result. Yes, the speed of a ball upon release is important. But we know that there are other factors at play, because the players at the receiving end of it say so. And ultimately, who would you rather face? A bowler that a machine says is fast? Or one that a human says feels even faster?

Tuesday 21 June 2016

Seven tricks to speed up Google Chrome

Samuel Gibbs in The Guardian

Many would say Chrome is the best browser out there. It’s certainly the most popular, used by more than half of the online world. But it’s a beast that can slow your computer to a crawl if left unchecked.
Multiple tabs, dodgy extensions and over-active plugins can leave you feeling like you’re using Windows 3.1 on a pre-Pentium 486, without the turbo switched on.
So here are few quick tips to help bring Chrome back under control, reduce its impact on your computer and speed up your browsing.

1) Get rid of any plug-ins you don’t use

Chrome plug-in settings.
 Chrome plug-in settings. Photograph: Samuel Gibbs for the Guardian
One of the easiest ways to speed up browsing is to cut back on your plug-ins. Type the following into the Chrome address bar and hit enter:
chrome://plugins
Click disable on any plug-ins you want to turn off.
If a page requires a particular disabled plug-in it will have a notice saying so instead of the video or audio element.

2) Make your remaining plug-ins ‘click to load’

Content settings for Chrome.
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 Content settings for Chrome. Photograph: Samuel Gibbs for the Guardian
For the plug-ins you want to keep, you can still do more to reduce their impact on Chrome. You can stop media that requires plug-ins, like Flash, from loading without your explicit say so.
There are a variety of extensions to do it, but Chrome’s built in settings for plug-in control are easy to activate.
In the Settings menu under “Show advanced settings” and Privacy, click on Content settings and scroll down to Plug-ins. Check the button for “Let me chose when to run plug-in content”.
When something like a Flash video attempts to load, all you have to do is right-click on the disabled plugin image and select “Run this plug-in” if you want to see it.

3) Remove or disable unnecessary extensions

Extensions settings in Chrome
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 Extensions settings in Chrome Photograph: Samuel Gibbs for the Guardian
Extensions are one of the best bits about Chrome, but each one adds bloat to the browser and therefore can eat up more of your computer’s memory and slow it down.
Click the hamburger menu in the top right of Chrome, mouse over “More tools” and click on “Extensions”. Or you can type the following into the address bar and hit enter:
chrome://extensions
Either uncheck the “Enabled” box to simple disable to extension, or click on the trash bin to fully remove the extension.
Disabling it allows you to re-enable it at any time, which is useful for extensions that you use only every once in a while, such as a rolling full-page screenshot utility. Removed plugins can always be reinstalled from the Chrome Web Store, but it’s a few more clicks.

4) Suspend your tabs

The Great Suspender Chrome extension
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 The Great Suspender Chrome extension Photograph: The Great Suspender
Chrome can be quite manageable with only two or three tabs open, but when you have upwards of 10 open at any one time it can bring even the most powerful computer to its knees by sucking up all the available memory.
There are two approaches to handling multiple tabs.
Extensions such as the Great Suspender allow you to suspend the tab and remove it out of memory after a certain length of inactivity without closing the tab in your browser. A suspended tab can be reloaded by simply clicking on it, and that way you don’t lose what you were looking at but also don’t cripple your computer with dozens of active tabs.
The downside is that if the site changes or you go offline you can’t recover the suspended tab. The Great Suspender allows you to whitelist some sites, stop a tab being suspended if it’s receiving input such as a text box or prevent a tab from being suspended on an ad hoc basis.

5) Create saved browser sessions

Session Buddy Chrome extension
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 Session Buddy Chrome extension Photograph: Session Buddy
Instead of suspending tabs individually extensions such as TabCloud+ andSession Buddy allow you to save a whole browser window full of tabs at once. You can then close them all at once, dramatically reducing Chrome’s load on your computer.
When you want to resume working on the saved tabs you can reload them all exactly the way they were in one complete browser window. It carries the same downside as the Great Suspender, meaning restored tabs are loaded fresh from the internet, so if anything has changed or the site’s no longer available then you won’t be able to restore the tab.

6) Turn off background prefetching

Prefetch settings in Google Chrome
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 Prefetch settings in Google Chrome Photograph: Samuel Gibbs for the Guardian
Somewhat counter intuitively, if your computer is struggling to handle Chrome, turning off Chrome’s automatic prefetching service, which attempts to predict where you’ll go next and loads at least some of that page in the background, can actually speed up your computer by reducing Chrome’s load.
To try it out, in the Settings menu, listed under “Show advanced settings” and Privacy, uncheck the box marked “Use prediction service to load pages more quickly”.
It could slow down your browsing by stopping prefetching, but it could help the rest of your computer by reducing Chrome’s load on it a little. Only recommended for very slow computers.

7) Use data saver

Data Saver extension for Chrome
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 Data Saver extension for Chrome Photograph: Google
And finally, if it’s not your computer slowing your browsing down but your internet connection, Google’s Data Saver service can help.
It puts all non-encrypted internet traffic through a compression system hosted on Google’s servers, reducing the amount of data Chrome downloads per page and speeding up page loading on slow connections.
It will also reduce your overall browsing data usage, which can be helpful for metered connections.
To use Data Saver simply install the extension. Be aware that all pages visited that are not using HTTPS connections of incognito tabs will be seen by Google if using Data Saver.

Thursday 20 February 2014

The psychological dominance of Mitchell Johnson


Jon Hotten in Cricinfo
How do you stop Mitchell Johnson?


Beginning a post with that question naturally implies there is now going to be some kind of an answer. Well, there won't be one here, beyond the obvious, and that is that time will stop him, as time stops them all. He bowls with the ghosts of Larwood and Thommo and Holding and all of the other terrors behind him. (My own personal nightmare? Sylvester Clarke, the brooding Grendel of The Oval, who would come and knock on the hotel room doors of opposing batsmen to let them know exactly what he was about to do.) Johnson has, in a few short months, entered the realm of men who have exerted a strange psychological dominance with the overwhelming pace of their bowling.

The compelling aspects of the Johnson story lie there, because the hold he has is not just on batsmen, it is on the collective imagination of everyone watching him bowl. As Russell Jackson observed in the Guardian newspaper this week, each Johnson spell has become event television. The thrilling news the Centurion Test brought with it was that the Ashes was no one-off: if Johnson could do his thing away from home against Test cricket's best team, then it can happen anywhere to anyone. After a single game, there are echoes of what he did to England, which was to induce a kind of deep-rooted demoralisation that extended beyond the field and into the psyche (he was not playing alone, of course, but he was a spearhead). It was as if he had pulled out a pin that held the team and organisation together, and the unit just sprang apart - injury, illness, retirement, disharmony all had their way.  - injury, illness, retirement, disharmony all had their way.
As the Cricket Australia Twitter account reported a little too gleefully - Ryan McLaren will miss the second Test with Johnson-induced concussion. There is also a run of luck that feels familiar: Dale Steyn stricken with food poisoning, Morne Morkel falling on his shoulder, and other phenomena not directly connected to Mitch but part of a general entropic slide. Just as England had players central to their strategy reaching the end of the road, so South Africa are absorbing the loss of Jacques Kallis: it's hard to think of a single player more difficult to replace. The captains of both teams happen to be left-hand openers, and Mitch is regularly decapitating both.
At the heart of all of this, as many have observed, is Johnson's pure and thrilling speed, channelled now into short and violent spells in which he bowls either full or short. This is the game reduced to its chilling basics. And yet there is mystery here too, and while unravelling it offers no answer to stopping Johnson, it may explain a little further what is causing such devastation.
The speed gun says that Johnson is bowling at speeds of up to 150kph, areas that other bowlers have touched. Because of the way in which speed guns work, deliveries of the sort that skulled Hashim Amla and Ryan McLaren registered more slowly due to where they pitched. (I'm sure that was great consolation to both players as the ball thudded into their heads.)
However, as the great Bob Woolmer revealed in his book The Art And Science Of Cricket, the nature of speed is not absolute because it is relative in the eyes of the batsman facing it. His research showed that the very best players - those who are euphemistically referred to as "seeing the ball early" - are actually reacting to a series of visual clues offered by the bowler in the moments before release.
Players who have faced Johnson speak of the sensation of the ball appearing "late" in his action, as his arm swings from behind his body. This is perhaps a combination of a couple of factors: the "clues" that Johnson offers in his run-up and delivery stride might be slightly less obvious than in other bowlers, and that his already ferocious pace is magnified by the extra micro-seconds that a batsman takes to pick the line and length of the ball (all the more impressive given that Johnson essentially only offers two lengths, and little variation on his themes).
Thus, with Mitch, the flexible nature of speed perception is working in his favour. Only the truly blessed - AB de Villiers, Kevin Pietersen et al - can play him with a little more certainty.
Pietersen was moved to tweet last week about the huge difference between 140kph and 150, just as his near-namesake Alviro was dismissed with a waft to the keeper. He said that you can "instinctively" play the wrong shot in those circumstances. What he was driving at was that Johnson offers no time for anything other than instinct, no margin to correct that first thought.
This is theory, of course. What can't be conveyed as easily is the psychological pressure that speed exerts. Players are wobbling to the crease with their minds consumed by thoughts of what he can do, and it becomes a self-fulfilling prophecy. South Africa are on a slide that will take tremendous resolution, as well as skill, to stop. In Smith they have one of Test cricket's most redoubtable men, and in de Villiers and Amla two of the most sublimely talented. It is absolutely fascinating to watch, and Mitch has done the game a great service in his phoenix-from-the-flames revival. This is cricket at its sharpest physical and psychological point.

Tuesday 18 February 2014

How Mitchell Johnson's speed scrambles the mind


South Africa thought they were well prepared to face Australia, but their plans overlooked the extra pace of Mitchell Johnson
Mitchell Johnson
Mitchell Johnson in full-speed mode during his devastating display in the first Test win over South Africa. Photograph: Themba Hadebe/AP

THE JOHNSON PROBLEM

Russell Domingo, South Africa's coach, never played first-class cricket. But he is a whizz with numbers. "I am," Domingo told Firdose Moonda, "very driven by technical and strategic aspects and analysis." AB de Villiers says of Domingo: "He likes his stats." No doubt, then, that his team thought they were well-prepared. Hashim Amla said before the first Test with Australia: "I don't think in this series there's too many surprise factors." Mitchell Johnson? "We've played against him before," said Faf du Plessis. "It's nothing we haven't seen … we're ready." All Australia's talk, Graeme Smith said, was just so much "bull". South Africa's batsmen had their plans, ones based on experience and analysis. "Everyone has a plan," as Mike Tyson put it, "'til they get punched in the mouth."
At 85mph, a ball takes 0.52sec to travel 22 yards. That's less time than it takes Usain Bolt to complete his first stride, and a little more than it takes you to blink. It's how long a batsman has to spot the length and line of the delivery, pick a shot to play, and then pull it off. To do it right, he needs to judge the position of the ball to within around three centimetres, and time the arrival of the bat to within three milliseconds. Any further, any sooner, any slower, and the ball misses the sweet spot. Put like that, hitting a cricket ball begins to seem like a preternatural act, as impossible as pinching a fly from the air with a pair of chopsticks.
They say it takes a minimum of 100 milliseconds for the brain to produce even the simplest action, and around double that to do something only a little more complex, like flicking a light switch. Benjamin Libet, a physiologist at the University of California, found that it took between 400 and 500 milliseconds for the brain to complete all the processes needed to produce a subjective experience. In cricket, the time constraint imposed by the speed of the delivery often exceeds the time available to process information. Against fast bowling, a batsman operates at a speed that outstrips his own consciousness. So how is it done?
It's not that the best Test batsmen have quicker reactions than anyone else. As Peter McLeod, a member of Oxford University's Department of Experimental Psychology, explained to John McCrone in the New Scientist: "There is surprisingly little difference between top-class athletes and good, fit ordinary people. In laboratory tests of reactions using unskilled tasks, most people show much the same reaction time of about a fifth of a second."
In his book Wait: The Art and Science of Delay, Frank Partnoy breaks that half a second down into still smaller chunks. Roughly, the first 150 milliseconds is seeing the ball. The last 100 milliseconds is spent playing the shot. In one of his studies, McLeod found that it is impossible for any batsman – he tested Allan Lamb, Wayne Larkins, and Peter Willey – to correctly react to any deviation the ball makes in the final 200 milliseconds of its flight. What matters then, is that chunk in the middle, the 150 milliseconds between seeing the ball and playing it. Partnoy calls this the "ball identification stage", a phrase he borrowed from the tennis coach Angel Lopez, who says similar processes are at work when a player returns a serve. It's what happens in this little window that separates the best from the rest.
When the ball is released, you and I might see a blur and have time enough to think through the first two letters of the curse we'll finish when the ball has passed. A batsman sees an ordered set of possibilities. He draws on information he has about the pace and style of the bowler, the condition of the pitch, and his own form. Add to that what he gathers from the anatomical position of the bowler during delivery, and finally, most importantly, what he observes during the first few milliseconds of the ball's flight.
After that, it is all anticipation. No one, despite everything your school coach ever told you, actually watches the ball on to the bat. Instead, the batsman's eye vellicates to the spot where he thinks the ball will bounce. The skill of a batsman, McLeod says, "lies in how they use visual information to control motor actions once they have picked it [the ball] up". It can't be taught, but is honed over hours of practice and play. We call it muscle memory.
At 95mph, a ball takes 0.47sec to travel 22 yards. That extra 10mph robs the batsman of 0.05sec. Which seems like nothing at all. But it's not. McLeod found that 0.05sec is the difference between a club and a Test cricketer. "We precisely measured how long different players took to swing and when they began their swings," McLeod explained. He looked at a range of players, from "true amateurs to top professionals". And he found that the professionals were quicker, "though not by much – just in the range of tens of milliseconds quicker". McLeod says: "What matters crucially is just a tiny time window of about fifty milliseconds in all. That makes all the difference."
Fifty milliseconds. The difference between an amateur and a pro, between 85mph and 95mph, between Mitchell Johnson and Jimmy Anderson. "There is," Kevin Pietersen tweeted last week while he was watching the Test, "a HUGE difference when facing someone at 140kmh compared to 150kmh … When you are facing someone as quick as Mitchell, your instinct occasionally makes you do things you shouldn't. PACE causes indecision."
The process must be disrupted, too, by the fear of being hit. The instinct to avoid being injured is even more ingrained than that of hitting the ball and the two can pull in opposite directions. It was telling that De Villiers, the one batsman who played Johnson well, explained afterwards "once you don't have that fear of getting hurt then I feel you play a lot better."
You could see that indecision in the first innings dismissal of Graeme Smith, who spotted the short ball, shaped to hook it, then changed his mind, and ended up spooning the ball to slip. It's only a little more speed, and a little less time. But it's enough to skew the complicated subconscious calculations of the best batsmen, accustomed as they are to having 50 milliseconds more to work with. Such slender margins, but such significant differences.