capacity and multitasking Flashcards
Why is it important to be cautious of multitasking?
Even when we do just one task, there are limits to cognitive capacity as all processes take time, and there are limits to the input of any one process. Capacity limits become even more obvious when resources must be shared between tasks, i.e. have to get more than one task done at a certain time. Limitations to multi tasking are important to be aware of theoretically and practically (human error has consequences).
When does dual task interference occur?
When we try to do tasks simultaneously due to competition for shared resources. When we try to switch between tasks, the overhead includes: set-shifting or task-switching costs, retrospective memory and prospective memory.
What are other demands on executive control during multitasking?
planning, scheduling, prioritising, and coordinating the two task streams. Troubleshooting, problem solving when things go wrong or unexpected conditions arise. So, multitasking is not a single competence and executive control processes are critical
What studies have been conducted into driving stimulators?
relative risk of mobile phone use and drinking by Strayer et al. Driver in simulator: fellows pacer car in slow lane of motorway for 15 mins, tries to maintain distance. Drivers usually alcohol showed more aggressive driving (harder breaking) but did not show an increase in talking on hand held phone device
What has been found about using hands free devices when driving?
Reduced up to 50% of periphery anticipatory glances to safety-critical locations, e.g. parked lorry obscuring a zebra crossing. Reduced again by 50% with later recognition memory of objects in the driving environment. Also an increased probability of an unsafe lane change.
Crash risk data suggests that passengers are sensitive to a driver’s load and can help stop hazards.
How can we measure dual task inference in a lab?
Measuring performance on task A and B alone and then combined. We can then see if performance on each task deteriorates when the other must also be performed
What findings have been discovered about dual task interference in labs?
Competition for use of specialised domain-specific resources e.g. parts of the body or brain modules with two continuous speech inputs that cannot simultaneously be understood or repeated.
Competition for the use of general purpose processing capacity
Limited capacity of executive control mechanisms that set up and manage the flow of info through the system and/or sub optimal control categories.
What does performing a spatial tracking task interfere with?
the use of visual imagery to remember things as both use visuo and spatial working memory
What did Kahneman propose?
a pool of general purpose resource that is shared among concurrent tasks e.g. mental energy, attention, effort. The capcity of this general purpose might vary over people, within or over states of alertness, level of sustained attention i.e. diminishes with boredom or fatigue and increases with time of day apart from post lunch dip.
If the sum of capacity demands does not exceed available total, there is no interference. However if the sum does exceed, there will be interference and increasing the difficulty of one task should reduce the capacity available for the other task. It is hard to know how much capacity a given task should use.
What did Allport investigate and what did he propose?
music tasks to students, either task A or B. they had relatively little practice. In the experiment they had to do the dual task for each combination of easy and hard. They found surprisingly that errors were no different with or without current sight reading and sight reading did not influence the difficulty of the shadowing.
Allport proposed that there is no central general-purpose processor/resource. Pairs of complex input-output translation tasks can be combined with little or no interference if they use non overlapping modules. So the idea of a general purpose central processor seems unnecessary.
But, even when the tasks use completely different modules, some interference may arise due to coordination and control demands e.g. error in one task briefly slows the other.
How is practice related to dual task performance?
Tasks which cannot be combined without interference becomes easier to combine with practice e.g. when learning to drive. Spelke et al 1975- very difficult dual tasks for ppts but some ppts showed little dual task interference, surprisingly because they had a lot of practice. Practicing one task automates it and reduces need for executive control of the constituent processes.
What was Broadbent’s objection to Allport type experiments?
With pairs of continuous tasks like shadowing and sight reading there is some predictability in the input i.e. we can anticipate but there is a substantial lag between input and output, so there must be temporary storage in WM of input and or output. So, there could still be a central processor switching between the two tasks.
This is known as the psychological refractory period (PRP); two choice reaction time tasks, stimulus onsets are separated by a variable, v short interval (the stimulus onset asynchrony). Seems to be some evidence that some central processing must be happening although it is not necessarily evidence that this is the central processor switching.
What is Pashler’s theory on response selection?
response selection is the bottleneck and can be performed for only one task at a time. If the second stimulus arrives and is identified it must wait until the response selection mechanism is free
