A Tone Sequence Following a Complex Rule

 

Humans show evidence of being able to preattentively extract rather complex rules governing a stimulation sequence. One of the most extreme examples in the literature comes from a paper by Paavilainen, Arajarvi, and Takegata (2007), as described in chapter 6 of the book.

Here is a sequence of sounds following the rule used in that paper. It is composed of four possible stimuli: a high frequency tone and a low frequency tone, each with either a short duration or a long duration. Can you find what is the rule that govern the sequence?

Study now the figure below. It illustrates the rule governing the sequence - stimuli marked by S follow the rule, stimuli marked by D do not (this is NOT the sequence you have just heard, which follows the rule without any exception).

Can you figure out what is the rule governing the sequence now?

 

 

 

 

 

 

 

 

The rule underlying the sequence is the following: a short tone is followed by a low tone (which can be short or long, with probability 0.5 each), and a long tone is followed by a high tone (which can be short or long, with probability 0.5 each).

Here's the sequence again. Can you follow the rule now?

Paavilainen et al. (2007) reported that even subjects who were instructed about the structure of the sequence could not reliably indicate deviations from the regularity. Nevertheless, they had a significant MMN. Thus, somewhere in their brain, the rule governing the sequence was presumably extracted, and deviations from the rule were detected.

 

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