Week 10 Topics • Lecture 10-1 • Types of Actions • Simple Reaction Time • Choice Reaction Time • Hick-Hyman Law • Lecture 10-2 • Speed-Accuracy trade-offs • Variables affecting Choice RT
Selection of Action • Types of actions (Rasmussen, 1980, 1986) • Skill-based: execution of highly-learned procedural memory—occurs largely outside of awareness • Rule-based: execution of simple “if-then” rules—imposes some working memory load • Knowledge-based: execution of actions based on extensive review of information in the environment and long-term memory – classical decision making
X RT Time Modeling Simple Reaction Time Effects • Criterion model • Two parameters • Aggregation rate of the stimulus (bottom-up) • Criterion set (top-down) • Action taken when criterion amount of aggregation reached • Effect of Stimulus Intensity • Sensory evidence aggregated (integrated) over time • Stimulus intensity affects rate of information aggregation
X RT Time Variables Influencing Simple Reaction Time • Temporal Uncertainty • warning signals mayprecede imperative stimulus • Warning Interval (WI): interval between warning signal and imperative stimulus • Lowers criterion (top-down effect) • Example: amber traffic light
Variables Influencing Simple Reaction Time • Effect of Variations in Warning Interval (WI): • WI short and constant (e.g., 0.5 s) • Temporal uncertainty reduced or eliminated • RTs shorten to nearly 0 • WI long or variable • Temporal uncertainty is increased • Uncertainty in internal timing mechanism increases linearly with duration • Simple RTs increase, reach maximum of 700ms
Variables Influencing Simple Reaction Time • Expectancy • Modeled as a criterion shift • Faster RTs • more false alarms • If WI is varied within a block, expectancy increases for longer WIs • EXAMPLE: Van Der Horst (1988) Vehicle controlled traffic lights • Driver expects the light to remain green since he knows the light senses his vehicle • RT to yellow light is delayed by a second!
Variables Influencing Choice Reaction Time • Amount of information transmitted is important • Choice RT requires operator to map stimulus to response -- information must be transmitted • More complex decisions (requiring more information) require longer to initiate • Information Theory: Three variables influence information conveyed by a stimulus • Number of possible stimuli • Probability of a stimulus • Context or sequential constraints
Information & Choice Reaction Time • Hick-Hyman Law • Choice RT increases linearly with magnitude of stimulus information • Hyman (1953) also varied the probability and sequential expectancy (context) of a stimulus • Information theory: unequal probabilities reduce the average amount of stimulus information • Mean RT for block of trials is shortened by this reduction of information accordingly, thus
Stimulus Frequency & Choice Reaction Time • Fitts, Peterson, and Wolpe (1963) • Examined RT to highly frequent and rare events • Prediction of Hick-Hyman • frequent events have little information, rare events have high information • fast RT for frequent events, slow RT for rare events • IMPORTANT IMPLICATION! • RT for real world tends to take much longer than in lab studies • Summala (1981) Time to break in response to a roadway obstacle is estimated to be 2-4 seconds • Why?
Accuracy and Choice Reaction Time • Speed-accuracy trade-off • Tendency to make more errors as you try to respond faster • Hick-Hyman: constant bandwidth for information transmission • Constant bandwidth mean that if speeded response doesn’t allow for all information to be transmitted, then not enough information will be transmitted for accurate responses • Human performance does not exactly follow the constant bandwidth assumption
Speed-Accuracy Operating Characteristic • SAOC curve • Similar to P(H) & P(FA) in SDT • Analogous to the ROC curve in SDT • Bias toward speed or accuracy is analogous to bias in SDT toward increasing hits or reducing FA accuracy stress Good (fast & accurate) log[P(correct)/P(error)] Poor (slow & sloppy) speed stress RT
System design and the Speed-accuracy Tradeoff • Certain design features seem to automatically shift performance along the SAOC • Auditory presentation enhances speed emphasis • Aircraft designers use auditory displays only for critical alerts that require quick responses • Presentation of more information will tend to slow performance and increase accuracy • Older adults tend to have an accuracy-emphasis • Stress can induce a speed emphasis • Some nuclear power regulations require operator to take no action for a period of time after a fault