|-Monocular occlusion training optimizes gaze performance of novices in complex skills|
-Monocular occlusion training improves kinetic visual acuity & binocular fusion
-Having access to speed & time of a moving object improves object location predictions
-Visual working memory can contaminate visual perception
-Visual perception is 80% memory based
-Improving visual working memory would improve visual perception
-Hitters’ prototypes need to constantly be updated & recalibrated to better predict pitch trajectories
Visual Perception & Memory
The American Psychological Association defines visual perception as the awareness of visual sensations that arises from the interplay between the physiology of the visual system and the internal and external environments of the observer. Visual perception is constructed in our brains using the information gathered from our vision. It is theorized that visual perception is constructed using 80% memory and 20% new visual sensory input. (Bornstein, 2009) In the construction of the brain’s mental model of events, the brain is constantly making inferences to piece together a mental simulation of predicted events and can override the original accurate information. (Polk, 2018) The hitter doesn’t see the pitch in real time, but rather as the brain’s best guess of the expected outcome. If hitting is a guess of the expected outcome how good is our brain at predicting pitch trajectory? Recent research has provided evidence that visual working memory can contaminate our visual perception. (Costandi, 2011) This can become troublesome for the hitter as the brain can infer the wrong trajectory patterns for incoming pitches. This lack of accurate information could also carry over to future at bats. Visual working memory has the ability to store 3-4 items and with the MLB average pitches per plate appearance being 3.83 it could prove beneficial to improve a hitter’s visual working memory. (Kamholz, 2014, Luck, 2007) Spatial memory is the ability to recall information from the brain when a task requires a movement solution to a desired location and where objects were when the event occurred. Kelling et al., also suggested that training to improve timing and situational factors would create better results when pitch preflight information is included.
The question should be asked what information do hitters use to create their trajectory predictions? There is theory of memory categorization called the Protoype Theory. Your brain creates a prototype for each pitch category that is the average of all the pitches you’ve seen in that category (for example; a fastball category). This prototype is constantly being updated. (Polk, 2018) This could explain why pitches that have average descent angles, spin rates and vertical break are the pitches hitters have the most offensive success with. These pitches match every hitters’ prototype pitch. Prototype models assume that for each category people retain a single specific “prototype” and that other category members will be compared against their created “prototype”. (Oppenheimer, Tenenbaum, & Krynski, 2013) Using Rapsodo Pitching data the “prototype” fastball has 2250-2350rpms and an average vertical break of 13 inches to 15 inches. Fastballs have an average descent angle of -6 degrees. (Blast Motion, Nathan 2015, Bahill, & Rybarczyk, 2019) With these numbers being the averages of pitches experienced, hitters will have calibrated their pitch trajectories to these metrics. Several studies have also shown that humans have built in, internal models of the effects of gravity on a projectile. (McIntyre et al., 2001) When a hitter sees a high spin fastball that fights the effects of gravity, the perception of the flight path of the pitch contradicts the internal model of expected gravitational pull on the baseball. Hitters have preconceived memories and calibrations of pitch trajectories and how the baseball will descend based on the effects of gravity. Hitters are using these expectations to calculate their collision prediction models.
Optical illusions of ball flight can also contaminate what a hitter perceives to be happening during the flight of a pitch. Witt and Proffitt (2008) stated “We perceive the world in term of our abilities to act on it.” Witt and Proffitt (2004) also showed that visual perception of the size of the baseball can be perceived differently based off your on-field success. Visual perception can create the illusion of the rising fastball and a curveball breaking much later and sharper than it actually does. (Bahill & Karnavas, 1993) Hitters have reported seeing a fastball rise from a pitcher, however a baseball would have to travel 113mph and have 3100rpms in order to rise. (Kagan, 2017) Mitigating optical illusions in a hitter’s visual field will allow for better collection of visual input. Higuchi et al., (2013) theorized that hitters are predicting trajectory only using ball speed and are miscalculating pitch trajectory due to lack of information in regards to how spin rate effects ball flight. The collection of more accurate visual input will allow the hitter will to create more accurate collision prediction models due to better visual perception.
Flash Lag Effect, Gaze, & Eye Dominance
Flash lag effect is the moving of an object that is perceived ahead of the aligned flash of light into our photoreceptors. Our visual response is delayed and this delay causes our eyes to not have the immediate location information of perceived moving objects. (Maus, Ward, Nijhawan, & Whitney, 2012) The delay from retinal image motion to the first acceleration of a tracking movement in the eye is 90ms. (Khoei, Masson, & Perrinet, 2017) It also takes up to 100ms for the brain to predict the trajectory of the baseball. (Anwar, 2013) By the time the brain has registered the pitch and the eyes have begun pursuit tracking, the eyes and brain are forced to catch up and predict the expected position of the baseball in flight. When predicting a moving objects expected position researchers have found that people can make more accurate predictions when they have access to information regarding the speed and timing of the object’s rhythmic patterns. (MIT, 2018)
There are two types of eye movements typically used while tracking a baseball smooth pursuit tracking and saccades. Smooth pursuit tracking of an object doesn’t have the angular velocity capacity to accurately track an incoming pitch. An incoming pitch can reach an angular velocity greater than 500 deg/sec. While the eye’s smooth pursuit tracking has been found to reach up to 120 deg/sec. Paired with the 30 deg/sec angular velocity of the head and gaze velocity still lags behind at 150 deg/sec. (Bahill & LaRitz, 1984) Since the eyes can’t physically keep up with the baseball during a smooth pursuit, the brain will have to make inferences as to where the pitch will cross the plate.
Saccadic angular velocity has been shown by researchers to reach angular velocities as high as 900 deg/sec. (Fuchs, 1967) (George, & Routray, 2016) However, information during a saccade is suppressed as the brain deems the information as unimportant to the task. Researchers have theorized that the suppression of this information is either from the eyes losing the localization of an object or light into the eye is dimmed and suppressed during the saccade. While our saccadic eye movement is ten times faster than smooth pursuit tracking it is believed that we are essentially blind during a saccade. (Gray, 2017) Research by Skavenski and Hansen (1978) demonstrated that participants could accurately strike a target with a hammer during a saccade even though the participants reported not being able to see the target. Exactly how blind is a hitter during a saccade? What information can the brain still process during a saccade?
Optimizing the performance of a hitter’s gaze would mitigate perceptual illusions. Several studies have shown that using monocular training can have positive training results. Heinen and Vinken showed that gaze performance can be optimized in novices via monocular training of a complex skill in gymnasts. Monocular training was shown to increase the performance of college players in a bunting task by improving their kinetic visual acuity. (Honda et al., 2008) Kinetic visual acuity is the ability to identify approaching moving targets. Monocular training of hitters has shown that hitters perform better when using their dominant eye during a hitting task. (Hofeldt, Hoefle, & Bonafede, 1996) Sheynin, Proulx, & Hess found that temporary monocular occlusion actually improved binocular fusion. Binocular fusion creates one stable image using both eyes and enhances visual sensitivity, visuomotor coordination, and improves depth perception. When binocular rivalry is present from two incompatible images the brain can switch back and forth from its preferred visual perceptual eye dominance and the non-dominant eye becomes less sensitive to visual input. (Blake & Boothroyd, 1985) In short two eyes are better than one, but training one eye at a time will improve the performance of both.
Hand-eye dominance has shown to delay skill acquisition of certain tasks. Rifleman who were crossed hand-eye dominant did not learn new marksmanship skills as quickly as those with matched hand-eye dominance. (Jones, Classe, Hester, & Harris, 1996) In contrast a study done on laparoscopic surgeons showed that hand-eye dominance did not affect the surgeons ability to perform the surgical task. Rather it was depth perception that hindered the surgeons’ abilities. Surgeons with depth perception deficits were able to improve their depth perception. (Suleman et al., 2010) Research by Hofeldt, Hoefle, and Bonafede showed that binocular vision contributes to localization of an incoming pitch, but the dominant eye influences hitting a baseball more than the other. How much will hand eye dominance effect the skill acquisition of monocular hitting training? There is a visuomotor delay of 14-21ms from the non-dominant eye when compared against the dominant eye. Could this delay be improved?
Discussion & Application
When training hitters using monocular training we added proprioceptive modalities to the drills with bats of various weights, lengths, and center of masses. We tracked hitter’s metrics using a Rapsodo Hitting Unit and Blast Motion Sensors per eye. Our question of training focus was should we work to strengthen the dominant eye or should we focus on improving the non-dominant? We chose to focus on improving non-dominant performance. Our hitters started with the drills off the tee and then slowly progressed to high velocity rounds off the machine. We saw improvements in bat speed, exit velocity, and rotational acceleration. Because skill acquisition is multi-sensory the belief we had was constraining multiple senses (visual & proprioceptive) at one time would lead to faster adaptations. The brain prefers visual information and mitigating visual perceptual misinformation will improve the visuomotor performance of hitters.
Mitigating visual perceptual misinformation would include educating hitters on pitch physics and providing specific visual examples of pitch flight movement patterns. Hitters need to recalibrate their internal models away from one league-wide prototype pitch to a specific pitcher’s prototype pitch. Providing velocity and time of each pitch would prove beneficial as MIT showed participants could better calculate an object’s predicted path when they were provided access to time metrics. Righteye would provide important data to study what impacts monocular training made on gaze performance. Improving visual working memory capacity would improve a hitter’s recall of pitch flight during at-bats and games. This could be done using any form of pitch recognition software, if the developers were willing to build a visual working memory component into their software. Creating a program that asks hitters to recall pitch locations and trajectory patterns from current and previous pitches from a previous at-bat or game would improve their working memory capacity. In my previous application of this style of training we cut team strikeouts in half and saw a decrease in batted ball spin rate peaks and smaller deviations in spin rates. Using monocular training would have the biggest impacts on swing decisions and contact quality based on my previous experience with novice hitters.
Knowing that visual perception is mostly based in memory we should be ensuring a hitter’s memories are accurate, properly calibrated, and free from biases and illusions. Finally, this would improve the hitter’s intuition at the plate. Intuition is formed from previous experiences, while experience is influenced by perception. If visual perception is contaminated, then intuition from the hitter will be based on misinterpreted experiences.
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