Grip selection without tool knowledge: end-state comfort effect in familiar and novel tool use

Area of Science:

• Cognitive Psychology
• Neuroscience
• Human Motor Control

Background:

• The end-state comfort (ESC) effect describes adopting uncomfortable initial postures for a comfortable final posture during reach-and-grasp actions.
• While influenced by tool orientation, task goals, and cooperation, the cognitive underpinnings of the ESC effect are not fully understood.

Purpose of the Study:

• To investigate the role of semantic tool knowledge and technical reasoning in movement planning.
• To determine if the ESC effect observed with familiar tools extends to novel tools.

Main Methods:

• Twenty-six participants performed reach-and-grasp tasks with familiar and novel tools.
• Conditions included varying tool orientation (handle up/down), task (transport/use), and social context (solo/cooperation).

Main Results:

• The ESC effect was replicated with novel tools, demonstrating that semantic tool knowledge is not essential.
• Habitual grips were observed with familiar tools even when unnecessary, suggesting interference from established movement programs.
• Effects of tool orientation, task goal, and cooperation were consistent across familiar and novel tools.

Conclusions:

• Movement planning relies on goal comprehension, which can utilize semantic knowledge, technical reasoning, or social skills.
• End-state configuration dictates beginning-state comfort, driving the ESC effect.
• Semantic knowledge is not a prerequisite for the ESC effect; cognitive processes guide movement planning.