Comparison of the effect of hard and easy mental arithmetic upon blocking of the occipital alpha rhythm

The intensity of blocking of the alpha rhythm of the EEG induced by the solution of five Hard mental multiplications has been compared with the intensity of blocking induced by five Easy mental multiplications in 36 normal subjects. From predictions derived from the application of two hypotheses concerning the intensity of blocking, it would be anticipated, firstly, that blocking would be more intense in the Hard tasks, if their solution required increased mental concentration and, secondly, that insofar as “higher thought” processes are more extensively required in the solution of Hard tasks, then blocking would be less intense in Hard tasks than in Easy tasks. However, the findings of the experiment have been that blocking is of the same intensity in tasks of both kinds. Possible reasons for this are discussed.

Hard tasks differed from Easy tasks, with regard to the relation of EEG changes and performance. It is thought that different mechanisms may underly the solution of the two types of task.