Articles:Eye tracking studies of normative and atypical development

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Contents

Goal

This paper seeks to provide a sense of why/how eye tracking measures have been used with children and adolescents. It will then appraise these measures as tools for probing development.

eye tracking measures

allows for non-invasive measurements of...

cognitive processes

  • visual–spatial attention to object perception
  • memory
  • language.

socio-emotional processes

  • motivation
  • response to different types of rewards
  • aspects of social information processing.

Eye tracking data-richness allows for researchers to make strong inferences, and give the researcher access to data that would be difficult (if not impossible) by other means.

saccades

ballistic eye movements aimed at bringing objects into foveal vision

  • Externally guided saccades (prosaccades): assessed through visually guided saccade tasks, where participants are instructed to look at a visual stimulus as soon as it appears.
  • Internally guided saccades: executed in the absence of a visual stimulus
    1. made to a location opposite from a visual stimulus (antisaccades)
    2. predicted (pre- dictive saccades)
    3. remembered location of a visual stimulus (memory-guided saccades) fall under this category.

Data:

  • duration, peak velocity
  • amplitude
  • gain (saccade amplitude/stimulus amplitude)
  • latency to initiate the saccade

Saccade Common Measures (pg 287)

  • Duration, peak velocity & amplitude of the saccade Gain (saccade amplitude/target amplitude)
  • Latency to initiate the saccade (RT)
  • Variability of saccadic RTs
  • Frequency of express saccades (saccades with very short RTs, i.e., between 80 and 130 ms) Corrective saccades (saccades to the correct location after an initial error)
  • Premature saccades (saccades prior to target onset despite instructions to fixate)

Gap & Overlap Common Measures (pg 287):

  • Gap effect (reduction in average saccadic RT when there is a temporal gap between fixation and target) * Increase in average saccadic RT when there is a temporal overlap between fixation and target

Antisaccade Task Common Measures (pg 287):

  • Accuracy (whether the saccade was in the correct direction)

Memory-guided saccade task Common Measures (pg 287):

  • Spatial accuracy of the saccades (distance error)

Predictive saccade task Common Measures (pg 287):

  • Frequency of predictive saccades for targets whose location and/or timing is predictable


smooth-pursuit eye movements

We use this to track small objects that move relatively slowly and smoothly. This is usually accomplished by instructing participants to visually track a small stimulus that moves at a relatively slow and predictable velocity along a horizontal path.

Formulas:

  • peak (or mean) gaze velocity divided by peak (or mean) target velocity. Low gain scores = "difficulty in matching gaze to target velocity, indicating inefficiency in the functioning of the pursuit system."
  • root-mean square error (RMSE): taking the square of the difference between target and gaze positions at each artifact-free point during pursuit, averaging the squares, and then taking the square root of this average. (RMSE; Clementz, Iacono, & Grove, 1996)
  • compensatory and intrusive saccades dur- ing tracking (Hutton & Kennard, 1998; Ross, Hommer, Radant, Roath, & Freedman, 1996)

Phases:

  • initiation phase (‘‘open-loop’’ pursuit):
    1. occurs during the first 100–120 ms
    2. retinal motion signal - depends on bottom–up information
  • maintenance phase (‘‘closed-loop’’ pursuit):
    1. top–down guidance of the pursuit system

Pursuit Common Measures (pg 287):

  • Root-mean square error (the difference between target and gaze position during pursuit)
  • Position gain (gaze position/target position)
  • Velocity gain (gaze velocity/target velocity)
  • Compensatory saccades (to catch up with the target) Intrusive saccades (saccades that anticipate the target’s location and ‘‘square wave jerks’’)
  • Initiation phase (pursuit during the first 100–120 ms)
  • Maintenance phase (pursuit after the first 100–120 ms)


fixations during scene/face perception
  • we normally make 3–4 saccades a second and pause in between (fixate) for 300–400 ms at a time this allows us to take in the information at the fovea and to decide where to fixate next.
  • people look at informative regions. They also tend to return to the same regions rather than covering the whole area of the picture
  • eye movements DO NOT reflect a "passive" type of perception but represent "active", goal-directed movements.
  • almost all fixations fall on task-relevant objects

Active fixation tasks Common Measures (pg 287):

  • Intrusive saccades during fixation

Scene/face perception tasks Common Measures (pg 287):

  • Location and sequencing of fixations Duration of fixations
  • Distance between fixations
pupillary dilation
  • regulated by the amount of light.
  • task-specific recruitment of cognitive resources

Tonic changes in pupillary diameter are influenced by general factors, such as level of arousal, anxiety, and stress

Rapid dilation due to internally or externally generated cognitive and emotional stimuli

Pupillary dilation tasks Common Measures (pg 287):

  • Peak pupilary dilation Latency to peak pupillary dilation

Children

There have been an enormous amount of research dealing with the developmental nature of eye tracking data,

  • has been used to examine the effects of medications in ADHD.
  • the effects of monetary rewards and punishments on antisaccades in adolescents with depression or anxiety (Jazbec et al., 2005)
  • how adults with spider phobia process pictures that include spiders (Rinck & Becker, 2006)
  • demonstrated that depression in adults is associated with ruminatory tendencies for negative or personally relevant stimuli (Siegle et al., 2003a).
  • children with dyslexia were trained to exert greater control over internally guided eye movements
  • "In a recent study extending this line of research to adolescents, investigators showed that monetary rewards and punishments had greater effects on antisaccade parameters in adolescents than in adults"(Jazbec et al., 2006).

maturation of working memory capacity and inhibitory skills are both likely to play a role in improvements in the ability to execute antisaccades.

"young children have poor voluntary control over fixation, leading to express saccades or to extremely long saccadic RTs. The youngest children had a high frequency of antisaccade errors (close to 50%), which decreased to 10% by age 15 and stabilized after age 20. " (pg. 298)

According to Eenshuistra, Ridderinkhof, Weidema, & van der Molen, (2007) the developmental improvement in antisaccade accuracy from age 8 to young adulthood was better explained by improvements in working memory capacity than in inhibitory control.

  • brainstem and cerebellar regions mediating accuracy and peak velocity of prosaccades were mature by age 8
  • oculomotor regions involved in fast responding to visual targets (including disengagement and shifting of attention, and sensorimotor transformations) continue to mature through adolescence.
  • Prosaccade RTs improved gradually with age until 15–20 and increased slightly after 30, another study also showed similar results in prosaccade RTs improving gradually between 6 and 28
  • Antisaccade RTs and errors showed steep decreases between 9 and 15, and continued to improve until age 25

Quotes

Resources

Eye Tracking in infancy (2004), Simion and Butterworth (1998), and Von Hofsten (2004)

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