🧩 Cognitive Chronometry & Decision Theory | Donders & Hick's Law

Simple vs Choice Reaction Time: Hick's Law & Cognitive Latency

The difference between simple and choice reaction time is cognitive decision latency: Simple Reaction Time (SRT) requires reacting to a single stimulus with a single fixed action (averaging 200 ms to 250 ms), whereas Choice Reaction Time (CRT) requires identifying which stimulus appeared and executing the correct corresponding response (averaging 300 ms to 450 ms). Governed by Hick's Law, reaction time increases logarithmically as the number of alternatives multiplies, adding 100 ms to 150 ms of neural processing delay per bit of decision complexity.

Simple Reaction (Type A): 200–250 ms

Choice 4-Way (Type B): 350–450 ms

Recognition (Type C): 280–340 ms

Hick's Law Overhead: +100–150ms/bit

How does the human brain process choices versus raw reflexive triggers? Discover the stages of cognitive information processing, Donders' subtraction method, and why decision-making multiplies reaction latency.

Simple Reaction (Type A)

1 Stimulus → 1 Click

Measures raw sensory-motor nerve conduction (~250ms).

⚡ Test Simple Reflex

Choice Stroop Test (Type B)

4 Conflicting Color Choices

Measures cognitive discrimination latency (~380ms).

🎨 Test Choice Stroop Latency

Type A: Simple RT

200–250 ms

1 stimulus → 1 response. Sensory detection + motor execution only. No decision overhead.

Type C: Recognition RT

280–340 ms

Go / No-Go task. Multiple stimuli, but respond only to target. Adds stimulus discrimination time (+50ms).

Type B: Choice RT

350–450 ms

N stimuli → N distinct responses. Stimulus discrimination + response selection (+150ms).

What Is Donders' Subtraction Method in Cognitive Chronometry?

In 1868, Dutch ophthalmologist Franciscus Donders revolutionized psychology by measuring the exact duration of human thought using his subtraction method:

Cognitive Stage	Isolated Duration	Mathematical Derivation	Anatomical Brain Region
Sensory & Motor Baseline	200–250 ms	Type A RT	Retina / Cochlea → Primary Motor Cortex (M1)
Stimulus Identification	40–60 ms	Type C - Type A	Parietal / Temporal Association Cortex
Response Selection	80–120 ms	Type B - Type C	Dorsolateral Prefrontal Cortex & Basal Ganglia

How Does Hick's Law Model Reaction Time as Choices Increase?

Hick's Law mathematically defines choice reaction latency as a logarithmic function of possible alternatives:

RT = a + b × log₂(n + 1)

Where a is baseline simple RT (~200ms), b is processing speed per bit (~150ms/bit), and n is the number of equally probable alternatives. Moving from 1 choice (0 bits) to 4 choices (2 bits) increases reaction latency by approximately 300ms.

Can Intense Practice Turn a Choice Reaction into a Simple Reaction?

Yes, through overlearning and motor chunking. When an athlete or gamer repeats a specific decision thousands of times (such as dodging an enemy flash or braking at a specific corner), the prefrontal cortex offloads processing to the basal ganglia and cerebellum. This creates an automated stimulus-response mapping that eliminates cognitive selection delay, reducing choice RT close to the simple 200ms baseline.

FAQ

Simple vs Choice Reaction Time FAQ

Everything you need to know about Hick's Law, Donders' experiments, and decision times.

What is the primary difference between simple and choice reaction time? ▼

Simple reaction time involves detecting a single predictable stimulus and executing a single predetermined action (e.g., clicking on green), taking approximately 200–250ms. Choice reaction time requires identifying which stimulus appeared and selecting the corresponding correct response among multiple alternatives, taking 300–450ms.

What is Hick's Law and how does it predict reaction time? ▼

Hick's Law (Hick-Hyman Law) states that choice reaction time increases logarithmically with the number of possible alternatives: RT = a + b * log2(n). Doubling the number of choices adds roughly 100ms to 150ms of cognitive processing latency.

What is Donders' Subtraction Method in cognitive chronometry? ▼

In 1868, Dutch ophthalmologist Franciscus Donders developed three reaction tasks: Simple (A-Reaction), Choice (B-Reaction), and Recognition/Go-No-Go (C-Reaction). Subtracting Simple RT from Recognition RT reveals the duration of stimulus discrimination (~40ms), while subtracting Recognition RT from Choice RT isolates response selection time (~80ms).

How does the Stroop Effect increase choice reaction time? ▼

The Stroop Effect occurs when the semantic meaning of a word conflicts with its font color (e.g., the word 'RED' printed in blue ink). The automatic urge to read the word interferes with color identification, adding 80ms to 150ms of prefrontal cortex processing delay.

Why is choice reaction time more relevant to driving and sports than simple reaction time? ▼

Real-world driving and sports situations almost never involve simple reactions. A driver must decide whether to brake, steer left, or steer right when an obstacle appears. A goalkeeper must recognize the ball's spin and dive left or right. These choices require cognitive processing governed by Hick's Law.