SDT & Vigilance

Vigilance vs. Sustained Attention

Mackworth Clock Task

How/Why does vigilance decrease over time? (also check the theories section)

occurs most often when one needs to detect a weak target signal (not when the signal is highly salient)

4 supervisory system processes

Brain regions

SDT & Vigilance relation

What factors affect vigilance performance?

Theories

SDT Basics

Vigilance:

  • stay focused during boring tasks (long period of time)
  • monitoring & detection of rare events & weak signals eg. air traffic control
  • the stimulus processing is rather a simple detection or discrimination (not including higher executive functions)
  • low criticaievent rate
  • no warning signal (you can't rest, unpredictable)
  • top down driven

Sustained Attention: more like an umbrella term

  • also long lasting task
  • high critical event rate
    usually a warning signal (you can rest during trials)
  • bottom up & top down
  • large black pointer in a large circular background like a clock
  • the pointer moves in short jumps, ca. every second
  • at infrequent/irregular intervals, the hand makes a double jump
    --> detect when the double jumps occur

established the vigilance decrement: signal detection accuracy decreases after 30 minutes on task

At first, this might be easy & you would rarely lose track of the target. But with time, it becomes harder to maintain focus -> your mind drifts & attentional lapses become more frequent

can occur more quickly if the task demand conditions are high

vigilance decrement = decline in the rate of the correct detection of signals

requires allocation of cognitive resources & induces stress response -> harder to maintain attention in unchallenging, monotonous situations (inverse relation between cognitive challenge & effort required to sustain attention)

Resource Depletion/Mental Fatigue: depletion of attentional resources due to continuous allocation of attention

  • insufficiently energized task schema

set of control processes of a supervisory attentional system:

  • performing simple/repetitive tasks is based on activating a task schema (input-output rules)
  • sustaining high performance levels over time requires supervision/top down control
  • if it isn't continually used, a selected schema will gradually lose its activation -> irrelevant competing schema may take over

Boredom/Absentmindedness: mind wandering, insufficient inhibition of competing schema

Self-regulation account (combines both ideas):

  • imbalance between subjective costs (effort exertion) & benefits (intrinsic rewards) of maintaining vigilance over time
  • self-regulatory power is limited & gets depleted with prolonged use
  • self-control strength decreases over time & results in: diminished intensity of attention allocated to the task (mental fatigue), diminished goal maintenance leading to task-irrelevant processing (absentmindedness)

also consider motivational issues: switching of priorities

Filter Theory (Broadbent)

  • attending to the same information for long periods of time is prone to intermittent interruptions that tend to increase with time on tasks (filter is biased towards the selection of novel information)
  • support: vigilance tasks in which signals are presented for only a brief period will yield bigger decrement
  • increasing event presentation rate enhances the decrement because more events are presented within a given interval

Expectancy Theory:

  • observers keep track of past signal occurrences to predict future ones-> formulation of expectancies, which can be assisted by task situation
  • signal frequency is crucial

Inhibition & Habituation (not well supported)

  • vigilance decrement as extinction of conditioned response when that response is no longer reinforced
  • decline in detection rate = accumulation of inhibition (fatigue)
  • support: knowledge of results & rest abolish the decrement (+)

(re)activating/energizing task schema

inhibiting conflicting schema

monitoring the activation level of task schema

monitoring performance

Basal forebrain cholinergic system & LC: blocking the release of ACh in the forebrain with GABA impairs vigilance performance

Inferior Frontal Junction: setting up S-R connections, rule representation, in tasks with overt responses, in discrimination tasks, with temporally fixed event occurence (ooposite of midlateralPFC)

amygdala: role in recognition of emotional stimuli

Midlateral PFC: selective biasing & filtering, monitoring the input-induced activation level of task schema, continuous monitoring of relevant external events, in tasks with covert responses, in simple detection, in tasks with a variable temporal structure of event occurence

subcortical brain regions associated with arousal

Dorsomedial PFC/ Midcingulate Cortex (monitors performance & energetical state, reengagement in task-relevant processing, outcome monitoring), Anterior Insula (need for effort signaling)

  • pre SMA: control of motor output eg. motor preparation, facilitation, inhibition

Midbrain Tegmentum & Thalamus: in overt motor responses

Temporoparietal Junction: when task-relevant changes in environment are detected, when expectations about stimuli are violated, need for reorientation signalling

Cerebellar Vermis: anticipatory timing of motor output

Intraparietal Sulcus: selectivity, attentional priority signaling, in discrimination tasks, with fixed temporal structures

decision making under uncertainty

decline in Hits with stable or increasing rate of FAs -> reduction in discriminatory power of perceptual system

application of SDT to vigilance situations advanced the assessment of detection efficiency

parallel decline in Hits & FAs -> increase in response criterion

in vigilance situations, it is difficult to discriminate signals from noise -> overlap between N & N+S distributions

detection efficiency in vigilance situations assessed by the nr. of hits & FAs & by target detection tendencies

combining Hits & FAs data to indicate: response criterion placement + perceptual sensitivity -> sensory & decision processes

the greater the overlap between the two distributions, the lower the d (observer's sensitivity) -> more difficult to discriminate N from N+S

high Beta -> conservative; low Beta -> liberal

response latencies in vigilance situations can be accommodated within SDT:

  • latencies associated with Hits & FAs increased wit time at work (affirmative responses)
  • latencies associated with Misses & CR either decreased or remained stable (negatve responses)

typical reduction in detection efficiency in vigilance is associated with a progressively more stringent response criterion -> Beta increases with time on task (conservative)

  • it could be either criterion increment or sensitivity decrement

second order psychophysical factors: may not be immediately apparent to the observers, must be inferred form the experience of the task

  • frequency or higher probability of signal occurrence -> improved detection efficiency through effects on response criterion (not on sensitivity)

Factors affecting criterion placement:

  • manipulations of signal probability: increases in probability increase Hits & FAs (liberal criterion), decreases in probability decrease Hits & FAs (conservative criterion)
  • instructions given to observers
  • costs & payoffs associated with making affirmative or negative responses

first order psychophysiological factors: some physical parameter of the signal is altered

  • increasing signals' intensity, duration or predictability -> detection efficiency improves, increased signal enhances perceptual sensitivity
  • increasing the rate at which events are presented (event presentation rate) -> reduced perceptual sensitivity, impaired detection efficiency

Factors affecting the sensitivity decrement:

  • event presentation rate
  • type of signal- non signal discrimination (successive or simultaneous)
  • decrements in successive (relies on working memory) discrimination tasks withhigh event presentation rate (more than 24 per minute)
  • degraded stimuli
  • maybe overall level of task demands eg. increase in working memory load

CONS

  • only concerns vigilance decrement & doesn't explain general low performance levels (-)
  • increases in the frequency in which the signals are presented should increase the decline in detection efficiency (accelerate inhibition accumulation) but they actually reduce the decrement (-)
  • Event rate manipulation doesn't have an effect & also no behavioral evidence (-)

not supported: decrement in self paced vigilance tasks should be smaller

Receiver Operating Characteristic: illustrates perceiver's responses for many strategies (more bowed curve -> better sensitivity)

Assumptions:

  • Internal noise has a specific distribution across trials
  • Same noise distribution for N trials & S+N trials
  • Signal & noise add up linearly ie. don't interact
  • Decision is based on two consecutive processing stages (sensory stage/internal response + Decision stage/decision criterion)

Resource Theory (quite supported): perceptual sensitivity decrement seems to be controlled by overall task demands

  • prolonged performance may deplete the pool of resources