The effects of the compatiblity properties of to-be-ignored stimuli on responding to a target

The compatibility effect found in the flanker task is usually explained in terms of response slowing due to incompatible flanker properties. It is as yet unclear whether the compatibility effect is also due to facilitative effects associated with compatible flanker properties. An extension of the Continuous Flow model put forward by Eriksen & Schultz (1979) namely the "Accumulated Activation Strength Difference" (AASD) model is proposed that maintains both response facilitation - due to compatible flanker properties, and response slowing - due to incompatible flanker properties, takes place under conditions where there is response competition. A series of flanker task experiments were conducted that presented 2, 4 or 6 flankers and combined flanker types in terms of their compatibility. It was found that flanker conditions that contained an equal number of compatible and incompatible flankers generated faster RTs than conditions that contained purely incompatible flankers. There was also no difference in RTs for incompatible flanker conditions or compatible flanker conditions whether there were 2, 4 or 6 flankers. This suggests that the effects of compatible and incompatible flankers cancel each other out. Furthermore, another experiment varied the ratio of compatible to incompatible flankers in a 4 flanker array. It was found that the ratio of compatible to incompatible flankers within a stimulus array mediates the magnitude of the compatibility effect. There is some evidence that this effect also occurs across different stimulus dimensions. The model also offers an explanation for why no response facilitation is observed for compatible trials compared to target alone trials and can account for how the patterns of errors in flanker tasks usually mirror the RT data. However, the model is complete, for example, it makes no attempt to account for how neutral flanker properties affect responding.