Dual-Task Interference 2
In the first dual-task interference paradigm, you completed two tasks by making separate responses to a letter and then to a tone. Whenever both tasks require attention, you run the risk of encountering dual-task interference, especially if the spacing between stimuli is short. However, it does not matter if both tasks require quick responses or even if both tasks require responses at all. You will learn in this lab activity that what matters is whether or not the tasks both require attention.
Encoding and Timed Response
To demonstrate that what matters for dual-task interference is whether or not the tasks both require attention, you will do a dual-task experiment where the first task is an encoding task and the second task is a timed response to a tone. There are two labs related to dual-task interference. Make sure you have completed the first one, the perceptual refractory period (PRP) paradigm, before completing this lab. In the PRP paradigm, you were shown that when a person has to complete two tasks that require a quick response, performance on the second task has to wait until performance on the first task is complete. In this lab, the first task does not require that you do anything except to enter information into short-term memory. This is called encoding. You will then assess whether the second task will be affected.
For this activity, you will see a fixation + that you should focus on and press the spacebar to begin a trial. Then you will be presented with either one letter or three letters that you will need to remember. You will hear a tone that will be either high pitched or low pitched. Your task is to respond to the tone as quickly and as accurately as possible by pressing the âDâ key if it is a high-pitched tone and the âKâ key if it is a low-pitched tone. You can play the tones to get used to them before starting the experiment. After you indicate the type of tone you heard (low or high), you will be prompted to type in the letters in the order they appeared. You can then begin the next trial. The activity consists of 10 practice trials and 80 experimental trials. You will receive feedback on all trials. After finishing all trials, you will be able to see a summary of your results for trials where you responded correctly.
Attention Required for Encoding and Responding
One thing that you should notice from the results is that when letters and tones are spaced close together (e.g., a short 200- or 395-millisecond stimulus onset asynchrony), response times are slower. You should also notice a difference in response times depending on encoding load, that is, whether one or three letters are encoded. The results suggest that at short SOA participants are still encoding letters and must wait until the letters have been encoded to respond to the tone. There is dual-task interference under short SOA and high load (i.e., three at encoding). The pattern of results can be taken as evidence that encoding the letters and responding to the tone both require attention. But at long SOAs (e.g., 1350 milliseconds), there is no difference in response time to the tone at either the one or three letter loads. No dual-task interference exists because the SOA is so long that encoding of the letters is complete and the participant can respond to the tone as soon as it is presented. In the 1350- millisecond condition, the participant is no longer operating in a dual-task situation and therefore does not experience dual-task interference.