Divided attention, order of report and responses to immediately successive signals

Two effects, “divided-attention” and “order of report”, are operationally denned. Their relative contributions to the reduction in efficiency which accompanies the recognition of difficult nonverbal signals, presented simultaneously, is considered. Experiment I evaluated the two effects in the absence of a fixed order of report and emphasis instructions, confounding features of previous studies. The results showed: an overall impairment of performance with simultaneous signals; a contribution of both effects to the decrement, with a suggestion of the primacy of the “order of report” effect; and a significant interaction between the latter effect and modality, such that visual signals showed the greater effect. Experiment II using similar signals tested the assumption that simultaneity of presentation is a necessary condition for obtaining reduced efficiency with multiple signals. The assumption was only partially confirmed, a significant decrement in performance occurring only for the second of two successively presented signals. Similarities between the two sets of results are noted, as well as between these and modality differences obtained with verbal materials. Two possible accounts of the data are proposed, one based on “input”, the other on “storage” models of divided-attention. The hypothesis that subjects report the most clearly perceived signal first is rejected as an independent explanation.

Limited surgical excision as the basis of a comprehensive therapy for cancer of the breast

A comprehensive program of therapy has evolved with collaborating roles for surgery, pathology, radiotherapy, and chemotherapy. Our experience includes 131 patients with breast cancer treated at the Massachusetts General Hospital since 1956 by limited excision of the cancer. The tumors of 10 patients were noninvasive or sluggishly so; the patients received no further therapy. Because of the invasive character of their tumor, 121 patients received heavy postoperative irradiation. In 12 of these 121, the irradiation has been followed by immediate and prolonged chemotherapy. It is too soon to judge the effect of the chemotherapy, but survival rates of those treated by limited excision and primary irradiation compare favorably with those of patients treated by radical mastectomy.

Visual Feedback and Skilled Keying: Differential Effects of Masking the Printed Copy and the Keyboard

The results of three experiments are reported. They were designed to substantiate the importance for skilled keying behaviour of information derived from the printed copy and the keyboard. Experiment 1 showed that consulting the copy and the keyboard during transcription constituted part of normal keying activity and that the frequency of consultation was a function of the specific demands of the task..Experiment 2, with no requirement to correct errors, and Experiment 3, with a requirement to correct errors, involved the independent masking of the copy and the keyboard as well as on unmasked control condition. Both experiments showed that an adverse effect on performance, as measured by speed and accuracy, occurred only in the keyboard masked condition. Experiment 3 revealed an additional adverse effect on performance, as measured by the reduced percentage of errors corrected, which occurred only in the copy masked condition. It was concluded that the keyboard provides ' guidance ' information, permitting the appropriate co-ordination of fingers and keys and the location of unfamiliar keys by sight, and the printed copy provides ' feedback ' information concerning the commission of errors. It is argued that the results resolve a contradiction reported in previous research and suggest that visual feedback has a continuing role even in highly practised skills, such as keying.

Reduced efficiency and capacity limitations in multidimension signal recognition

The first part of Experiment I showed that subjects recognized difficult frequency and intensity signals significantly less well when these were presented together than when they were presented alone. It was estimated that contingent variability resulting from other dimension signal and response context occurring on the same trial accounted for a third of the reduction, and capacity limitations for the remainder. Efficiency on the two dimensions presented together was found to be related and two data subsets were identified for which no efficiency reduction occurred. In the second part of Experiment I subjects recognized correlated frequency and intensity signals and showed a significant improvement in performance over either dimension performed alone. The gain in efficiency was well predicted by the “integration” model of Green and Swets (1966) from one- but not from two-dimension performance. The result suggested that the reduction in efficiency associated with capacity limitations was a function not of the number of signals but of the number of difficult decisions. Experiment II replicated the first part of Experiment I with easy signals. Efficiency was the same whether the signals were presented together or alone. The result indicated that the reduction in efficiency with difficult signals was not due to response interference or to failures of post-recognition retention. The implications of the results for models of attentional capacity are discussed.

Some factors regulating auxin translocation in intact bean seedlings

Several factors which influence the translocation patterns of stem-injected indoleacetic acid, 2,4-dichlorophenoxyacetic acid, and 2,4,5-trichlorophenoxyacetic acid in bean seedlings (Phaseolus vulgaris L. cv. Stringless Greenpod) were characterized. The acropetal translocation of auxin from the site of injection is markedly sensitive to concentration in the range of 1.0 to 5.0 micrograms per plant. The antiauxin p-chlorophenoxyisobutyric acid enhanced translocation of 2,4,5-trichlorophenoxyacetic acid to the growing shoots and primary leaves. Translocation to the roots was unaffected by p-chlorophenoxyisobutyric acid while leaching of 2,4,5-trichlorophenoxyacetic acid into the nutrient solution was enhanced slightly. Steam girdling experiments revealed that translocation to the primary leaves was in the xylem. The protein synthesis inhibitor, cycloheximide, inhibited accumulation of 2,4,5-trichlorophenoxyacetic acid in young shoots, epicotyls, and roots and enhanced accumulation in the primary leaves. The relative exchangeability of auxin between xylem and phloem is discussed in terms of regulation of auxin movements in intact bean seedlings.