Negative priming in a sequence of dichotic listening trials

The previous studies had shown that presenting a single syllable that the participant was supposed to ignore made it less noticeable in an immediately subsequent pair of dichotic syllables. However, the rather artificial experiment situation allowed one to questions of the effect's generalizability. Further, we don't really know what the participant is doing when instructed to "ignore the first sound". According to my theory, the negative priming effect should appear in any situation where a recently ignored stimulus is repeated. As classical theories considered the dichotic listening situation in itself (an information funnel where two bits of information enter and one come out) to be resolved by attenuating one signal but also inhibiting the other signal, it occurred to me that I could simply loop the process, and make one dichotic selection constitute the priming process for the next dichotic selection, which could again prime the next dichotic selection and so on.

Thus, as the dichotic listening paradigm used in our group presents one syllable to be attended and one to be ignored, I could leave behind the somewhat convoluted prime-target task design I had used in my previous studies, and simply present a sequence of dichotic listening trials (without any attention instruction). I adjusted the on-line randomization of stimulus selection to make sure that 50% of the trials repeated one (but not both) of the stimuli presented on the previous trial. In the analysis of the trials with repetitions, I considered every trial n to be the prime for trial n+1. Whether the repeated prime syllable was expected to have a negative or positive effect on n+1, depended on whether the participant selected to attend it or not (for whatever reason) on the prime trial n. E.g., if trial n presents the syllables "Pa" and "Ta" and the participant selects "Pa", then "Ta" was considered to have been inhibited, and if trial n+1 presented "Ta" and "Da", then "Ta" should have a reduced likelihood of being selected. The results did indeed show such a negative priming effect. A converse positive priming effect was indicated, but failed to reach significance (although it was shown in a later study).

The main contributions of this study was (1) to show that sequence effects are apparent in even rather simple dichotic listening tasks without any convoluted priming procedure, and (2) that negative priming effects could be seen in a sequential task with free choices where the prime selection is made arbitrarily. This second point has some relevance for theoretical development, since at least some reading of previous negative priming theories stated that the prime selection would have to be based on a pre-defined selection criteria in order to cause subsequent negative priming effects. I began to formulate what I consider to be a more parsimonious model to account for priming effects, where different nodes in a network achieve different levels of activation based on the stimulus input, but also retains positive or negative activation from preceding selection.

Sætrevik (2010) A biased competition model accounts for negative priming in a free choice situation as residual effects of inhibitory conflict resolution - Neuroscience Letters