Key Concepts in Psychology: Summary of Reaction Time, Motor Skills & Sensory Feedback

Reaction Time Experiments

• Helmholtz (1850): Reaction time (RT) experiment origins.

  • Aim: Determine nerve information conduction speed.

  • Experiment: Stimulated frog nerve-muscle, measuring response latency.

  • Human version: Weak electric current on elbow/wrist, key press response.

  • Findings: Most time spent in the brain deciding whether to respond.

Donders' Elaboration

• Donders (1868): Three reaction time experiment types: 'a', 'b', and 'c'.

  • 'a' reaction: Simple reaction time task.

  • 'b' reaction: Choice reaction time task (mimic one of five sounds).

  • 'c' reaction: 'Go-no go' reaction (respond to only one of five sounds).

Subtractive Logic

• Mental algebra to calculate time for mental processes.

  • Discrimination time = 'c' - 'a'

  • Choice time = 'b' - 'c'

Wundt's Psychological Laboratory (1879)

• Explored Donders' proposals, introduced the 'd' reaction to address criticisms.

• 'd' reaction: Common response to stimulus detection, then identify the stimulus.

• Difficulties: 'd' RTs as fast as 'a' RTs; subjects' preparation differed.

Serial Stages in Information Processing

• Donders' logic relies on sequential processing.

• Sternberg (1969, 1975): Provided support for non-overlapping serial stages.

  • Memory Scanning: Subject identifies if a test stimulus was in a target set.

  • Varying target set size changes comparisons.

  • Reaction time increases linearly with set size (35-40 ms per item).

Regularities in Memory Scanning

• Constant search times across materials and subjects.

• Scanning rate varies by material type (digits fastest, nonsense syllables slowest).

• Practice reduces intercept but not slope.

• Positive and negative response latency functions have identical slopes.

• Exhaustive search, continuing even post-match.

• Additive effects: Independent variables affect different processing stages.

Hick's Law and Information Theory

• Merkel (1885): Response latency increases with choice extent.

• Hick (1952): Reaction time relates to information processed.

Information Theory Basics

• Quantifies 'how much', not 'what'.

• Focuses on uncertainty reduction.

• Information amount relates to event unlikelihood.

Information Theory Equation

• $H = \sum p<em>i \log</em>2{\frac{1}{p<em>i}}$, where $p</em>i$ is the probability of message i.

• Simplified: $H = \log_2{n}$, where n is equiprobable alternatives.

• Unit of information: BIT (Binary Digit, base-2 logarithm).

Hick-Hyman Law

• Response latency increases with choice extent.

Transmitted Information

• Adjustment for inconsistencies (errors) in subject behavior.

• Accommodates speed-accuracy trade-off.

Stimulus Discrimination vs. Response Selection

• Mapping ratio (stimuli to responses) affects uncertainty.

• Response uncertainty is more impactful than stimulus uncertainty.

Reconciliation of Sternberg and Hick

• Sternberg: Linear relation (reaction time and target set size).

• Hick: Logarithmic relation (reaction time and alternative stimuli).

• Increasing stimuli linearly affects reaction time.

• Increasing response alternatives logarithmically affects reaction time.

Motor Skill and Accuracy

• Woodworth (1899): Faster responses are less accurate; blindfolded responses can be as accurate as responses with sight if movements are quick enough.

• Keele and Posner (1968): Studied aiming responses at different time lengths.

  • Visual information ineffective for movements under 200 ms.

• Beggs and Howarth (1970): Turning lights out before movement affected accuracy.

  • Critical Time: 290ms for visually based adjustments.

• Coach's Advice: Keeping eyes on the ball is unnecessary during the last 0.25 seconds.

Ballistic Movements and Motor Programs

• Craik (1947): Aiming movements are ballistic (executed without central corrections).

• Motor Programme: Internal instructions for muscle coordination.

• Challenges: Assembling implicit responses or motor programs.

Movement Control - Sensory Modalities

• Bringing Object (hand) and Target (glass) into conjunction.

Distant Location of Object Requirements

• Vision is key, especially stereoscopic vision.

• Proprioception signals body part locations relative to each other.

Effector Localization - Alternatives to Visual

• Dead reckoning: Calculating position based on past movements.

• Proprioception is key.

Proprioception Mechanisms - Joint and Tendon Receptors

• Joint Receptors: Signal static angle and angle change rate.

• Tendon Receptors: Signal tension developed by muscles.

• Weight Judgments depend upon force and muscle actions.

Motor Constancy

• Motor Constant Mechanisms: Preserve relation between intent and action.