Better together: Contrasting the hypotheses explaining the one-target advantage

Area of Science:

• Human motor control
• Cognitive psychology
• Human-computer interaction

Background:

• The one-target advantage (OTA) describes shorter movement times to a single target versus sequential targets.
• The movement integration and movement constraint hypotheses offer explanations for the OTA.
• Previous research provides equivocal support for each hypothesis.

Purpose of the Study:

• To review and evaluate the relative support for the movement integration and movement constraint hypotheses in explaining the OTA.
• To determine the role of task difficulty, specifically index of difficulty (ID), in supporting each hypothesis.

Main Methods:

• Literature review of studies investigating the one-target advantage (OTA).
• Analysis of how different indices of difficulty (IDs) influenced the support for movement integration versus movement constraint hypotheses.
• Categorization of studies based on employed IDs (low: 1-4 bits, intermediate: 5 bits, high: 6-8 bits).

Main Results:

• Studies using higher IDs (6-8 bits) predominantly supported the movement constraint hypothesis.
• Studies using lower IDs (1-4 bits) predominantly supported the movement integration hypothesis.
• Studies with intermediate IDs (5 bits) showed support for both hypotheses.

Conclusions:

• Task difficulty (ID) is a critical factor in determining the explanatory power of the movement integration and constraint hypotheses for sequential goal-directed movements.
• The OTA likely always involves movement integration, with movement constraints playing a role when accuracy demands are high.