Attentional Blink
We are often presented with more stimuli than we can process. Since human cognition is limited in capacity, we use our attention to select some stimuli while ignoring others. This lab activity focuses on something called the attentional blink, which is the brief period of time when attention cannot be switched to a new stimulus while it is still being used to process a previous stimulus.
Temporal Limits of Attention
In a typical attentional blink paradigm, stimuli are presented one at a time for approximately 100 milliseconds each. The participant observes a stream of stimuli and determines whether specific target stimuli are presented to them. It is often found that participants are unable to identify a target if it is presented too soon after another target, as if the participants actually blinked (i.e., briefly closed their eyes) and missed it. The duration of the attentional blink is approximately 550 milliseconds, but after this time, normal processing resumes. Almost half a second is long enough to miss detection of words, flashing visual signals, and even some sounds. This finding is directly relevant to you if you attempt several tasks consecutively, like taking notes when you are trying to listen to a lecture.
Measuring the Attentional Blink
In this activity, your attentional blink will be measured during a series of 10 practice trials with feedback followed by 48 actual trials without feedback. On each trial you will be presented with a letter stream of 18 characters. Each will be presented for 20 milliseconds and then hidden for 80 milliseconds before being shown the next character. You have two things to do during the viewing of each trial’s letter stream. The first is to monitor whether an “F” or a “J” was presented. The second is to determine if an “X” was shown in the stream or not. At the end of each trial, you will be asked whether the F/J was present or absent, followed by another question about whether an X was present or absent. Try not to actually blink during the letter stream or that will confound the attentional blink results.
Your Attentional Blink Duration
The attentional blink hypothesis states that if the “F” or “J” is presented within 550 milliseconds of the “X” then you will not be able to detect the X. When your data are presented at the end of this activity, you will see your accuracy at detecting an X when it is actually presented as a function of the number of intervening characters between F/J and X. As the number of intervening characters between F/J and X increases so should your accuracy at detecting an X when it was actually presented. You can figure out the duration of your attentional blink by counting the number of intervening letters when your performance dropped below 75% and multiplying by 100 milliseconds.
Short-Term Consolidation into Memory
Information processing has multiple stages: perception, short-term consolidation into memory, response selection, response execution, etc. The attentional blink findings are consistent with attention being required for short-term consolidation into memory. If the attentional blink was not associated with processing the F or J into memory, there would be no change in target detection accuracy based on the number of intervening letters.