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# The Simon Effect Based on Allocentric and Egocentric Reference Frame: Common and Specific Neural Correlates

## Details

**Authors** Li et al.

**Year** 2019

**Publisher** Scientific Reports

**Discipline** Neuroscience

[Read it at the publisher](https://doi.org/10.1038/s41598-019-49990-5) 
10.1038/s41598-019-49990-5

## In authors' words

### Abstract

An object’s location can be represented either relative to an observer’s body effectors (egocentric reference frame) or relative to another external object (allocentric reference frame). In non-spatial tasks, an object’s task-irrelevant egocentric position conflicts with the side of a task-relevant manual response, which defines the classical Simon effect. Growing evidence suggests that the Simon effect occurs not only based on conflicting positions within the egocentric but also within the allocentric reference frame. Although neural mechanisms underlying the egocentric Simon effect have been extensively researched, neural mechanisms underlying the allocentric Simon effect and their potential interaction with those underlying its egocentric variant remain to be explored. In this fMRI study, spatial congruency between the task-irrelevant egocentric and allocentric target positions and the task-relevant response hand was orthogonally manipulated. Behaviorally, a significant Simon effect was observed for both reference frames. Neurally, three sub-regions in the frontoparietal network were involved in different aspects of the Simon effect, depending on the source of the task-irrelevant object locations. The right precentral gyrus, extending to the right SMA, was generally activated by Simon conflicts, irrespective of the spatial reference frame involved, and showed no additive activity to Simon conflicts. In contrast, the right postcentral gyrus was specifically involved in Simon conflicts induced by task-irrelevant allocentric, rather than egocentric, representations. Furthermore, a right lateral frontoparietal network showed increased neural activity whenever the egocentric and allocentric target locations were incongruent, indicating its functional role as a mismatch detector that monitors the discrepancy concerning allocentric and egocentric object locations.

### What they set out to do (purpose)

To identify the common and reference-frame-specific fronto-parietal correlates of egocentric vs allocentric coding.

### What they found (results)

Both egocentric and allocentric conflicts slowed responses; right precentral/SMA resolved conflict in a common frame, right postcentral gyrus was allocentric-specific, and right superior parietal gyrus detected mismatch between the two frames.

## Commentary

### In short

The brain codes space from different points of reference (egocentric vs. allocentric).

### In more detail

The brain encodes location relative to distinct points of reference (self-centered vs object-centered), so the same scene is simultaneously represented from multiple viewpoints with dissociable neural bases. Purpose: To identify the common and reference-frame-specific fronto-parietal correlates of egocentric vs allocentric coding. Finding: Both egocentric and allocentric conflicts slowed responses; right precentral/SMA resolved conflict in a common frame, right postcentral gyrus was allocentric-specific, and right superior parietal gyrus detected mismatch between the two frames. [Added 2026-07-30 as new evidence beyond the original 109; DSRP structural basis: P axiom (Point and View): egocentric vs allocentric frames are literally different points-of-view; extends the existing Vallar egocentric-frame entry.]

**Patterns it shows** P

**Added** 2026-07-30

**How to cite this** Li et al. (2019). The Simon Effect Based on Allocentric and Egocentric Reference Frame: Common and Specific Neural Correlates. Scientific Reports.