Simon's experiments and stimulus-response compatibility: hypothesis of two automatic responses

In Simon, Hinrich, and Craft's (1970) experiments, two factors, Stimulus-Response Compatibility and Position of Hands, are manipulated. The effects of these factors are not additive. Effects of Stimulus-Response Compatibility are usually explained by the similarity between the sets of stimuli and responses. This similarity leads us to suggest that, in these particular experimental designs, two automatic responses will be triggered by the presentation of the stimulus and consequently will be associated with two Stimulus-automatic Response mappings. These two mappings are shown to be positively (both Compatible or both Incompatible) or negatively (one is Compatible whereas the other is Incompatible) correlated, depending on the treatment combination of the two factors. Stimulus-Response Compatibility and Position of Hands. Consequently, the effects of Stimulus-Response Compatibility and Position of Hands are suggested not to be additive. The predictions inferred from this model are consistent with experimental data and Simon's conclusion.