"Heads or tails?"--a reachability bias in binary choice.

Area of Science:

• Cognitive Psychology
• Decision Science

Background:

• Individuals asked to simulate random sequences, like coin tosses, exhibit systematic deviations from true randomness.
• A notable, yet under-recognized, divergence is the tendency to initiate mental coin toss sequences with Heads.

Purpose of the Study:

• To investigate the phenomenon of first-toss bias in mental coin toss simulations.
• To introduce and explain the concept of 'reachability' as a general response bias.
• To explore the broader implications of this bias in various binary choice scenarios.

Main Methods:

• Analysis of existing datasets on simulated coin tosses.
• Experimental manipulation of instruction order (Heads vs. Tails first) to test bias reversibility.
• Conceptualization of the 'reachability' bias to explain observed patterns.

Main Results:

• Approximately 80% of participants initiated mental coin toss sequences with Heads.
• This first-toss bias was found to be reversible by altering the presentation order in instructions.
• The 'reachability' bias, favoring the initially presented option, was identified as the underlying mechanism.

Conclusions:

• The order in which options are presented significantly influences choices in binary decision-making.
• The 'reachability' bias extends beyond randomness cognition, affecting surveys and tests.
• Understanding presentation order effects is crucial for designing unbiased binary choice systems.