The Effect of Uncertainty on Reaction Time

Using various card-sorting tasks, this class experiment shows how choice reaction time increases with the number of bits processed in tasks having familiar stimuli and one-to-one stimulus-response compatibility. Students deal decks of cards during four timed exercises into a specific number of piles according to color (2 piles), suit (4 piles), etc., which represent a different level of uncertainty measured by bits of information processed. A second deal is conducted without regard to suit, color, etc. to determine and remove movement time from the total deal time. The relationship of the resulting reaction time and bits is shown in a graph of data generated in real time from the students' four class exercises. This demonstration can be used to introduce the concept of information processing, to explore what experimental factors could contribute to the resultant time, and to discuss real-life choice reaction time applications.