I spy with my QE - 3.1 Flashcards
visual perception
Almost half of the cerebral cortex is devoted to vision-related functions.
It follows then that the neural processes that transform visual information into the representations that allow us to perceive the world and interact within it, are central to brain function.
In sport – vision is by far the most important sense (although auditory and tactile information is also important)
This information is needed to successfully make decisions (anticipate) & perform goal-directed actions (movement)
Uiga et al. (2015) - Acquiring visual information for locomotion by older adults
older people focus couple of steps in front
eye-tracking
Gaze direction can be calculated by comparing the relative position and the relationship between the pupil (A) and corneal reflection – the glint (C).
Infra- red illumination of the eye produces the ‘bright pupil’ effect (B) and makes the tracking easier
overlaid with video
eye movements and gaze control
fixations
saccades
fixations
Gaze is maintained on objects or locations for sufficient time to allow information to be processed
Within 3 degrees of visual angle for 100ms or longer
(NB at least 180 ms needed to see an object and initiate a simple movement).
ends when deviate
saccades
Eyes move quickly from one location to another
Rapid jumps – bring new part of visual field into foveal vision
Range in duration from 60ms to 100ms
Saccades are the fastest type of eye movement, (max vel. of 500 degrees per second
We cannot pick up information during a saccade (saccadic suppression) - reason why all of our perceptions are different
eye movement metrics
no. fixations
gaze/fixation duration
scan path
no. of fixations
a concentration of a large number of fixations in a certain area may be related to a user’s interest in the object or detail presented in that area when viewing a scene.
gaze/fixation duration
gaze is defined as a number of consecutive fixations in an area of interest.
Gaze duration is the total of fixation durations in a particular area
longer for experts
scan path
the scan path is a line connecting consecutive fixations.
It can be revealing of a viewer’s visual exploration strategies and is often very different in experts and novices.
PCE in sport: a meta-analysis
Mann et al (2007)
systematic diffs in visual search behavs also observed, with experts using fewer fixations of longer duration, including prolonged QE periods, compared with non-experts
Mann et al (2007)
Expert-novice differences in Visual Search Strategy have been found in a range of sport settings including: racquet sports, baseball and volleyball
- Experts are better than non-experts in picking up perceptual cues, as revealed by measures of response accuracy and response time.
- Systematic differences in visual search behaviours; with experts using fewer fixations of longer duration, (including prolonged quiet eye periods), compared with non-experts.
- Several factors (e.g., sport type, research paradigm employed, and stimulus presentation modality) significantly moderated the relationship between level of expertise and perceptual-cognitive skill.
Mann et al (2007) - point 2
Experts (generally) have a lower search rate:
– Fewer and longer fixations
– Less scattered / More efficient
Expert athletes use their rich knowledge base to pick out the most salient aspects of the display.
In addition, lower search rates are associated with less saccadic suppression (and hence more time to process relevant information; Moran et al. 2002)
search rate
number of fixations / mean duration of fixations
visuo-motor control
Movements are guided by vision
Movements are more accurate when guided by accurate vision
Gaze tends to rest on a target before motor act is initiated and this visual information is used to guide action
The neural mechanisms regulating goal-directed movements profit from the accurate and timely spatial information of the foveated target
visually guided actions
task-specific (goal-directed) eye movements
– support the planning and control of manual action
– are present throughout action sequences for more complex tasks
- form of attention in brain - paying attention to goals and goals directing movement
Top-down instructions dominate gaze behaviour in the performance of visually guided actions
“The challenge is now to find out how descending attentional mechanisms control gaze during purposeful action” (Land 2009, pp.61).
the head tracks and gaze predicts: how the world’s best batters hit a ball
Mann et al.
track where will hit the bat
who are the experts they are using
QE
Defined as the final fixation or tracking gaze directed to a single location or object in the visuomotor workspace within three degrees of visual angle for a minimum of 100 ms.
The quiet eye has an onset that occurs before the final (critical) movement in the motor task, and an offset that occurs when the fixation or tracking deviates off the target by more than three degrees of visual angle for more than 100 ms (Vickers, 2007).
Basically….the last fixation to a target before moving
longer duration the better
QE - why useful?
It’s simple : your hands are controlled by your brain, which gets valuable information about what to do from your eyes.
As you perform a visually guided motor task, your brain needs to organize more than 100 billion neurons. These neural networks are informed by your gaze, and control your hands, arms and body as the stroke is performed (e.g., Land, 2009).
These networks will stay organized for only a short period of time; a window of opportunity opens that must be used when it is at its most optimal - brain has lots of other things to be doing
50% of brain taken up by visual cortex
info from eyes incredibly valuable when going to move
the specifics of the QE
interested in timing and duration
how do we know QE imp?
interested in timing and duration
- How long do performers track / aim at a target?
- When do they initiate this final fixation (QE onset)?
- When do they stop this final fixation (QE offset)?
how do we know QE imp?
- Proficiency Differences
- Effects of Anxiety
- Training
Empirical studies - types of tasks
whilst tasks require diff motor actions, perceptually they all ask subject to fixate on critical target area and to time acquisition of info so there is optimal coupling
Experts golf putt
focus on just one dimple of ball
average 2-3s QE
QE reflects the optimisation of visual attention for the planning and control of movement parameters
final fixation prior of initiation of back swing
Vickers argues that about 2s qQE periods optimal
3 key aspects of putt
- look at ball prior to initiation of stroke
- look at ball during stroke
- maintain dwell on ‘ball location’ just after stroke
control of goal-directed and stimulus-driven attention in the brain
want to use dorsal attention and less of ventral attention
From Wilson et al (2015)
more interaction from dorsal and less from ventral - focused state - smoother motor control output - get more info
pressure and QE
Increased anxiety disrupts effective attentional control (QE)… AND … subsequent performance
QE and choking: online control breaks down at the point of perf failure
putted until missed
final shot - also breakdown of QE
dwell - crucial to keeping perf going
QE and perf in sport: a meta-analysis .- Lebeau et al (2016)
look at effect sizes of diff QE studies
large effect size for diff between experts and novices
large effect size between QE period to perf
