734 t.SHALLICE AND P W.BURGESS The card also conains the following instructions:You are to spend as lit money as possible (within nd take as lit time as possi y o shop sho are not to anything not bought on the street (other than a watch)to assist you.You may do the tasks d nart of the ins ken th rt distance to a s hopping prec er he or she s as al rge street ending in the pedestr onend and lights e oth e be Nine c Resuls.Table s gives the numberruced by each of the patients.Each produced at SDs more t han the controls in the a e boundaries or leaving a shop with a newspaper without paying tthe info cand rather than the postcard:( either not carried out or not completed satisfactorily. TABLE 5.ERRORS ON MULTIPLE ERRANDS Cases 8 Task failu n failures 12 2 More than 2 SD worse than the control subjects. 一 and on the numbe The in the rate of error qed was place the back he instructron shee which by hen she br hop wit em t h utbuying anything)because when in the hop (a 11 she foundt the task was ting.Cases I and 2 both became ing he ne the previous day's aper.They had,so he walked out with it,incidentally breaking the buy ing rule He was pursue into the street by the shopkeepe e paid for it.A.H d just assumed th ors shop simply k about the location of that ype of shop (b He734 T. SHALLICE AND P. W. BURGESS The card also contains the following instructions: 'You are to spend as little money as possible (within reason) and take as little time as possible (without rushing excessively). No shop should be entered other than to buy something. Please tell one or other of us when you leave a shop what you have bought. You are not to use anything not bought on the street (other than a watch) to assist you. You may do the tasks in any order.' This second part of the instructions—the 'rules'—is then read aloud to the patient who is asked to repeat them. If the rules cannot all be repeated satisfactorily the procedure is repeated until they can be. The subject is then taken the short distance to a shopping precinct where he or she is asked to repeat the rules again. If there is any failure to reproduce the gist of any instruction the subject is reminded of it. It is then indicated to the patient where the limits of the test area are; they are very clearly demarcated by a large street ending in the pedestrian precinct at one end and a set of traffic lights at the other. The behaviour of the subjects while carrying out the activity is monitored by 2 observers and they are also debriefed after the task had been completed. Controls. Nine control subjects were tested. They were matched with the patients for age (mean 40, range 24-63 yrs) and NART IQ (mean 122, range 113-127). Results. Table 5 gives the number of errors produced by each of the 3 patients. Each produced at least 2 SDs more than the controls. Table 5 also shows the errors broken down into subcategories: (1) inefficiencies—where a more effective strategy could have been applied, e.g., entering the same shop more than once; (2) rule breaks—where a specific rule (either social or explicitly mentioned in the task) is broken, e.g., going outside the boundaries or leaving a shop with a newspaper without paying; (3) interpretation failure—where the requirements of a particular task are misunderstood, e.g., assuming that the information must be written on the birthday card rather than the postcard; (4) task failure—a task either not carried out or not completed satisfactorily. TABLE 5. Inefficiencies Rule breaks Interpretation failures Task failures Total errors ERRORS ON / 6* 5* 1 0 12* MULTIPLE Cases 2 9* 8* 1 5* 23* ERRANDS 3 5* 8* 1 4* 17* Control 1.4(1.1) 1.6(1.3) 0.4 (0.7) 1.1 (1.4) 4.6(2.1) * More than 2 SD worse than the control subjects. All 3 patients performed at the 5% level or worse, as estimated from the control data, on both the number of inefficiencies and on the number of rule breaks. There was no difference overall in the rate of errors of the other two types, although Case 3 produced more task failures. Thus 2 normal controls as well as the patients failed to provide the required information on the postcard, probably because the information required was placed on the back of the instruction sheet. Qualitatively the performance of the patients was even worse. They made types of error which were not produced by any control. Case 3 used a clearly irrelevant criterion inappropriately when she broke a rule (entering a shop without buying anything) because when in the shop (a chemist) she found it did not have a soap she especially liked; other cheap soap—which would have been at least as adequate for the task— was available. She also failed to note the time when starting. Cases 1 and 2 both became involved in social complications. Case 1 made the interpretative error of deciding he needed yesterday's newspaper (to find the coldest place in Britain on the previous day). He entered a newsagents and asked if they had the previous day's paper. They had, so he walked out with it, incidentally breaking the buying rule. He was pursued into the street by the shopkeeper who wanted to be paid for it. A.P. had just assumed that because a previous day's newspapers are generally worthless he could have one without paying. Case 2 produced a complex set of errors. Thus one series of actions began with his being the only subject to enter a shop simply to ask about the location of another type of shop (breaking buying rule). He was referred to a shop outside the allowed area, went to that shop (breaking the limit rule) and became involved in by guest on April 8, 2016 http://brain.oxfordjournals.org/ Downloaded from