Vertical consolidation considers those BPs which are addressed satisfactorily by the model and plays on the commonality of some JAs between observed instances to provide support for the model.
4 . 3 . 1 . Information is implicit in stored plans
The model maintains that some information may be stored implicitly in a task’s script. This information becomes explicit when the particular script is executed. However, it is thought possible to access this information in advance by mentally executing the task. For example, the following excerpt occurs as the subject is adding cheese to the sauce in the pan, i.e. as a product of real execution. The absence of mustard is not itself important for multitasking, but it is taken as an example of something which could have been brought up earlier and maybe acted upon.
S 1 “I notice there's no dried mustard which I might put into a cheese sauce, normally to save putting so much cheese into it - but seeing that we've got so much cheese, I don't think I'll need it - I’ll just go overboard on the cheese.”___________________
It is possible to find other cases in the protocol data where subjects do think ahead, or mentally execute the task, and so made explicit important information. E.g.:
S6 [just as he picks up the fish to start preparing it,]
“I mean a lot of the recipes you sort of know them in your head and you sort of plan them from ingredients that you know you have - like its just occurred to me now that you may not have any butter, for example, is this true? (There's some there) Oh, that's good - but that would have been a problem for example in that sometimes I might plan to do it this way and you might not have the stu ff... Yes, well it had
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occurred to me earlier actually, but I made a contingency plan that I could use a little bit of oil if it came to it.”
S5 “ so the potatoes ... I'll put on at about 10 past, after cutting them up. Do I have a kettle? (No), so I'll have to boil the water as well.”
S741 [whilst scrubbing potatoes, i.e. as a parallel mental activity]
“I'm now wondering about the trout, and as it was actually bought for me, I'm wondering whether or not I'll actually have to gut it.”_________________________ Also less important information becomes explicit. This may be a reflection of implicit information stored in plans, or it may be more an example of more general
association. In fact, irrelevant associated information of the general form “My Granny would have...” was very common in the protocols:
S3 “If there was a steamer, then its much better, because then you get the - you don't lose the vitamins as much as you do this way.”______________________ ________
4 . 3 . 2 . Behaviour is largely controlled by a schedule
First of all, it can be said that ALL the subjects voiced some sort of schedule, i.e. an intended sequence of (sub)tasks. After this it needs to be established that they engaged in activities in this order (which is only broadly true given the frequency of unforseen activities and/or the high level nature of the schedule) and that they did not repeat the decision making at the changeovers between activities.
For example, the following is a statement made by subject S7 very near the start of the exercise
S74 “OK, well the first thing that I've got to do is turn on the oven, for the roast
potatoes for later on, and the next thing that I've got to do is get the potatoes ready so that they can be par-boiled, and I'm going to need some hot water for the
potatoes so I may as well put that on next, erm, and I can get the carrots ready at the same time as I'm getting the potatoes ready, and I don't need to do anything to the fish for the moment. So that's what I'm going to do.”________________________ The actual order of activities performed, in the short term that the schedule seems to address, is as stated - turning the oven on, boiling some water, then preparing the potatoes and carrots.
Alternatively, subject S8 make the following statement of intent - i.e. his proposed
schedule, early on:
S8 “The potatoes will take a bit of time. But the fish takes 25 minutes, so I'll get on
^ n a p ie r *+
And, true to intention, he completes the preparation of the fish, and then decides to get on with the potatoes:
S8 so I'm now going to go into the potatoes, that's the next thing that’s er going to
take a bit of time.”
In the model, planning is considered to proceed in an opportunistic manner, where the plan is not constructed stricdy forward in time. Also, the final plan is considered to be partial in that actions are ultimately situated in some real, partly unpredictable, context. This is borne out by the data. For example, the following subject has already voiced a high level schedule which involves doing the potatoes followed by the fish. At this point, she has done the potatoes and is now about to consider the fish in more depth before proceeding:
S771 “And I'll just put them to one side and wash the knife, in case I need it in a minute,
which I probably will. Right, I'm just going to check now what I'm going to do with the trout now I think.”
Subject 2, on the other hand, has an a priori intention to put the potatoes in the oven and then turn over the the fish. In the event he does it the other way round:
S2 “Now this is a dodgy little exercise, ’cos I think these are going to spit, hang on, in fact I'm going to tum over the fish first before I put that in.”____________________ Given that there is a schedule, it is worth considering whether it is efficient; whether or not the subject is aware of a critical path goes someway towards indicating this. The critical path is that sequence of activities which determine the time that the whole job will take. One of the general instructions on the sheet given to subjects at the start of the experiment was that they should attempt to cook the meal in the shortest time possible, in addition to specifying that all the constituent parts should be ready together. To satisfy this criterion it is necessary both to identify the sequence of activities, and to start this sequence first. The other activities can then be arranged around it. Subjects varied in their appreciation of the critical path, which, assuming a perfect scenario, was as follows:
Task 1: Pre-heat the oven - Bake the fish
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Some identified this straight away, e.g.: S6 [Task 2]
“Well I mean, when I look at the menu, my first, erm, product, if you like, is to put them in order of preference, so that the potatoes are obviously erm are the first thing I’ll tackle”
The above was one of his earliest utterances after reading the initial instruction sheet. ‘Order of preference’ is taken to mean the chosen order of doing. Shortly after this, and as his first activity:
S6 “right, well I'm going to need an oven, so the very first thing I'm going to do is get
that oven on, get that heated.”
Other subjects only realised the Critical Path much later on, e.g. Subject S3:
This subject starts off by preparing the vegetables, and then prepares the fish, after which she is ready to cook it and turns the oven on - i.e. the first activity in the critical path. Shortly after she realises her error, and finds that indeed the job time is
determined by the critical path and that she has time on her hands.
S3 “I'm not quite sure, er the sauce is going to be too cold I think if I do it now, so I shall leave it as that. And the potatoes are going alright, so I should have put the oven on first. Well, I'm not quite sure what I’m going to do now, since I've got most of the things ready.”
4 . 3 . 3 . M ental W orkspace & P erfo rm an ce System can be concerned
w ith two d ifferen t tasks
This is not something which is readily evidenced by verbal protocols, since although they may represent the behaviour of the Mental Workspace, the location of the Performance System has to be filled in separately. Several instances of parallel mental activity have already been described above in other contexts. This section presents some others:
SI “So while I'm scrubbing the potatoes, I'll just read over what I'm going to be doing with the baked fish.”
and similarly, whilst scrubbing the last potato, but before finishing:
S746 “and this is my last potato, so I'm now beginning to think about my carrots and
Associated with the notion of not thinking about what you are doing, or even the cost of not doing so, is the prediction of certain classes of errors on the basis of models of attention in action (e.g. Reason, 1986). Such models maintain that the execution instructions / script / schema which runs off automatically, will follow a default set path or set of values based on past experience - i.e. learning. There will be choice points in such a sequence where the behaviour could be tailored to a specific occasion. However, this is taken to require the intervention of the Mental
Workspace. An error - i.e. an action not as planned - results when an intervention is missed, for example because the Mental Workspace is engaged elsewhere in some parallel mental activity. There are examples of such slips in the protocol data: 5 1 I've actually made sauce for two rather than for one, out of habit,”
52 “er in fact I've done too many potatoes, sorry about that, unthinking,”__________ Note that it is not possible to illustrate satisfactorily the relevant decision points and show that the Mental Workspace was indeed otherwise engaged at the critical
moment. Rather, the above are offered as examples of what would be expected given the proposed model.
4 . 3 . 4 . Monitoring
Monitoring is not strictly an expected behavioural phenomenon. However, it is the only observed manifestation of two other BPs - namely doing something in passing (“While I’m at it”), and internally triggered interruptions.
Interrupting an ongoing task to check on the state of another without any external trigger or event is very common. E.g.:
5 1 “Just check the oven, see if that's ready for the fish yet.”______________________ There is also evidence that there is some intention to monitor in advance:
52 “I'm not sure what the temperature is going to be like on this one - so I'll just have to check that they're simmering in a few minutes.”
“Need to check the potatoes from time to time as well.”________________________ And true enough:
S2 “The er, yes, I was going to check those potatoes.”___________________________ However, the intention to monitor (or not) is not reliable. Take the following example, in which the person decides that it is no longer necessary to monitor the
state of the potatoes, i.e. he is content to go into what could be described as a feedforward mode:
S5 “Checking the pan for the potatoes again - 1 think I can ignore that now because it seems to be boiling at a constant speed, so that should be ready at half past, along with the fish.”
but later he checks them anyway:
S5 “Checking potatoes again ... (Were you really concerned about the potatoes not boiling, or did you just fancy having a look?). I was just having a look.”
Given the phenomenon of monitoring in this way, a further complication arises in terms of a tendency, for example, to monitor several items in succession. This is assumed to result from their physical proximity:
SI “Let's have a look and check that the mangetout are coming up to the boil nicely, that's good, the potatoes are boiling well.”
There were only very few observed examples of externally triggered interruption, which may be a result of the particular job, or of the data capture and analysis. Of those which were observed, the following is a good example:
S2 “That fat is starting to smell very hot - I'm a bit worried about that. I think I'll turn down this slighdy”