Motivation and Motor Control: Hemispheric Specialization for Approach Motivation Reverses with Handedness

PLoS ONE, Vol. 7, No. 4, 2012

5 Pages Posted: 11 Nov 2012

See all articles by Daniel Casasanto

Daniel Casasanto

The New School for Social Research

Geoffrey Brookshire

affiliation not provided to SSRN

Date Written: April 26, 2012

Abstract

Background: According to decades of research on affective motivation in the human brain, approach motivational states are supported primarily by the left hemisphere and avoidance states by the right hemisphere. The underlying cause of this specialization, however, has remained unknown. Here we conducted a first test of the Sword and Shield Hypothesis (SSH), according to which the hemispheric laterality of affective motivation depends on the laterality of motor control for the dominant hand (i.e., the 'sword hand,’ used preferentially to perform approach actions) and the non-dominant hand (i.e., the ‘‘shield hand,’’ used preferentially to perform avoidance actions).

Methodology/Principal Findings: To determine whether the laterality of approach motivation varies with handedness, we measured alpha-band power (an inverse index of neural activity) in right- and left-handers during resting-state electroencephalography and analyzed hemispheric alpha-power asymmetries as a function of the participants’ trait approach motivational tendencies. Stronger approach motivation was associated with more left-hemisphere activity in right-handers, but with more right-hemisphere activity in left-handers.

Conclusions: The hemispheric correlates of approach motivation reversed between right- and left-handers, consistent with the way they typically use their dominant and non-dominant hands to perform approach and avoidance actions. In both right- and left-handers, approach motivation was lateralized to the same hemisphere that controls the dominant hand. This covariation between neural systems for action and emotion provides initial support for the SSH.

Keywords: motivation, emotion, handedness, EEG, alpha-power asymmetry, sword and shield hypothesis

Suggested Citation

Casasanto, Daniel and Brookshire, Geoffrey, Motivation and Motor Control: Hemispheric Specialization for Approach Motivation Reverses with Handedness (April 26, 2012). PLoS ONE, Vol. 7, No. 4, 2012, Available at SSRN: https://ssrn.com/abstract=2173829

Daniel Casasanto (Contact Author)

The New School for Social Research ( email )

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Geoffrey Brookshire

affiliation not provided to SSRN