# prinz1990: A Common Coding Approach to Perception and Action

tags
Perception, Brain

In this chapter, Prinz goes over evidence suggesting a shared coding between action and perception. He lays out empirical and theoretical evidence for a shared coding, and criticism for the separate coding approach. This is more directly linked to the Ideomotor Principle, and is some good evidence for having perception being dependent or apart of the behavioral responses.

## Separate Coding

This view holds that the afferent and efferent codes are incommensurate at all levels of the coding.

The most direct consequence of such a view is that there needs to be some type of transformation to couple the incommensurate codes.

$$f$$: AFFERENT $$\mapsto$$ EFFERENT

where $$f$$ is some unknown transformation, where the couplings produced are known as production rules linking codes of afferent information to efferent information.

$$f$$ has some features which are listed:

1. The couplings are arbitrary in the sense that any afferent code can get linked to any efferent code.
2. The couplings may differ in strength, depending on several factors (use, importance…)
3. They can be read from both sides, either specifying appropriate efferent codes under given afferent conditions, or appropriate conditions for given efferent codes.

The translation metaphor (Welford 1960, 1968): This metaphor views the codes from the afferent side, asking the question “How can given afferent codes become translated into corresponding efferent codes?” This requires a translation mechanism to link the codes.

The response choice metaphor (Welford): This metaphor views from the opposite side, asking the question “How can choice of one among several efferent codes be accomplished on the basis of afferent information?”

## Common Coding

He first presents common coding in terms of introspection. Asking the reader to find gaps between perception and action. This is a decent metaphor, but it relies to heavily on introspection (which is an extremely flawed empirical tool. And interesting metaphor, or thought experiment, is presented from James’ Principles of Psychology:

Consider, for illustration, a person who is instructed to press the left of two keys in response to stimulus A and the right in response to stimulus B. How is the intention to act according to this rule experienced? Though this is not particularly easy to tell, the best answer still seems to be the one suggested in James’ analysis of voluntary action: when we perceive the stimulus event (say A) we only need to think of the response event supposed to follow it (left key press) and - “presto!” - it happens by itself.

This account suggests the reduction of intentions to cognitions: when one wants to do something, the only requirement is to think of the intended action in terms of its ultimate distal result.

Taking these observations, he lays out the common coding framework. Percept code stand for events-to-be-represented (or afferent codes). While act codes stand for events-to-be-effected (efferent codes). (note: this difference is not correlated with the nature of the coded events and both can refer to purely environmental events or mixed environmental and bodily events. There is no distinction between env and bodyily events, but a distinction between event representation and event effectuation.