Margaret H. P. Broadbent

From detection to identification: Response to multiple targets in rapid serial visual presentation

In four experiments, words were presented visually at a high rate; as has been found previously, subjects could identify individual target words and must therefore have gathered some information even about the unreportable nontargets. The novel feature of this study was that there were frequently two targets in the list; the occurrence of the first target disrupted identification of the second for a subsequent period of more than half a second. This happened whether the target word was designated by a single physical feature or by the semantic characteristic of belonging to a specified category. The two situations did differ, however, in that unidentified targets of the first type still disturbed an accompanying second target, whereas those of the second type did not. The results are interpreted as meaning that a simple undemanding process of detection triggers other and more demanding processes of identification, so that the occurrence of the latter for one target interferes with their occurrence for another.

Anxiety and Attentional Bias: State and Trait

Abstract MacLeod, Mathews, and Tata (1986) found that anxious patients showed a tendency to react faster to a probe stimulus that appeared in the location of a threatening visual word rather than in that of a simultaneous neutral word. In 4 experiments, a total of 104 subjects drawn from the general population were tested on different variations of this task. A relationship to anxiety was confirmed, and it was shown that this relationship did not appear on animal names that also formed a semantically similar set and had an equal probability of being followed by a probe stimulus. Although the effect is therefore dependent on the content of the word, it builds up during the experimental session and is therefore likely to be due to increasing post-attentive awareness of the presence of threatening words. The most reliable results across experiments were found by using Trait rather than State Anxiety, and particularly by fitting a curvilinear relationship such that the exact degree of Anxiety makes little dif...

Recency effects in visual memory

A number of studies were conducted, in each of which a series of abstract visual patterns was presented, and the subject was then asked to choose which of two test items was in the list. The items contained specifiable visual features, and similarity could therefore be varied in a relatively known way. As in earlier studies by other workers with randomly generated patterns, a recency effect was obtained. However, this effect did not depend on similarity between the items in the list, or between them and an intervening activity. Such factors do in some cases affect the average level of performance, but not the magnitude of recency. Nor was recency abolished by tasks interposed between presentation and test. These findings suggest a general mechanism of short-term memory, rather than a specifically sensory one. However, the recency effect did depend on the similarity of location of items in the visual display. Thus there is some evidence for a specific sensory store, with items arriving more recently over-writing those which came earlier and which were similar in location.

Recency effects in memory, as a function of modality of intervening events

SummaryWord lists of fifteen items were presented to eye or to ear, with recall either immediately, or after a visual task, or after an auditory one. Instructions were to recall the last items first. An intervening task using the same modality greatly reduced recall of the last items presented; whereas a visual task did not do so for acoustically presented items. An auditory task reduced visual memory. These results suggest a specific auditory memory for recent events, over-written by subsequent auditory events.

Combining attributes in rapid serial visual presentation tasks

A series of three exploratory experiments sought to compare and contrast two broad classes of theory pertaining to visual information pick-up. One theoretical approach, exemplified by Keele and Neill (1978) and by Treisman (1977) emphasizes the relatively passive, parallel development of information codes, with subsequent attentional integration of contiguous codes into a percept. Another theoretical approach, exemplified by Broadbent (1977a) emphasizes the relatively active, sequential, recursive interrogation of a visual display in which the pick-up of each piece of information guides the perceptual system in its quest for more information. The manner in which separable attributes of visual information are picked up and combined was studied by manipulating the roles of different attributes in a rapid serial visual presentation (RSVP) paradigm. Observers were asked to report the name of a letter in a specified target colour; to report the colour of a specified target letter; to report the colour of a specified target numeral embedded in a list of letters; to report the colour of an unspecified numeral embedded in a list of letters; and to perform the latter two tasks without knowing in which of two alternating spatial positions the target might appear. Examination of the patterns of mis-combinations of attributes from target and non-target stimuli yields evidence both for and against each theoretical position, and suggests that the two might better be considered as modes of processing available to the perceptual system, rather than as intrinsic properties of that system.

Time of day as an instrument for the analysis of attention

Abstract The long-established effect of Eriksen and Eriksen (1974) is that distracting stimuli impair performance on a choice reaction if they arrive less than about 1 degree away from the reaction signal; but not if they are more widely separated from it. On the other hand, it is also known that people respond more quickly to a signal whose location they do not know, if the signal remains in the same position on successive trials (Tipper & Cranston, 1985). These phenomena look as if there is a spatial bias of attention, whatever the task being performed, and they can be explained by late or by early selection theories of attention. Following a failure to replicate the Eriksen effect, a series of further experiments was performed with minor variations. From the six studies totalling 128 subjects, it became clear that the classic effect is reduced or abolished in the afternoon, and further that this reduction of the effect is greater in individuals with high cognitive failure scores. On the other hand, the...

Articulatory suppression and the grouping of successive stimuli

SummaryTwo experiments required subjects to memorise for immediate recall lists of nine items, presented visually and grouped by threes. As each item followed the previous one in the same spatial location, it must have been temporarily stored until the whole group had arrived. In one experiment the items were digits; grouping could be detected by the fact that recall of the last two items in a group was heavily contingent upon recall of the first item. In the second experiment the items were letters, and some of the lists were made up of meaningful triplets of letters such as UNO. Grouping could be detected by the size of the difference between these lists and the meaningless ones. In each experiment, the extent of grouping was just as great if the subjects were asked to repeat an irrelevant sequence of sounds while memorising; although the recall under both conditions was of course depressed.It appears therefore that the temporary memory, in which the items are held before grouping, is not impaired by articulatory suppression; nor in these conditions could it have been a sensory store. The result is supportive evidence for the existence of an abstract, non-sensory, non-motor, working memory.

The Allocation of Descriptor Terms by Individuals in a Simulated Retrieval System

Abstract These experiments simulated the performance of people using a suggested retrieval system for personal notes and files. Four groups of subjects were observed each classifying 100 potential Christmas presents as they thought appropriate. Three groups totalling 24 subjects invented their own classificatory terms; not one person used mutually exclusive categories and their classifications could not therefore have been simply filed without some index or artificial aid. Retrieval of objects was very substantially better using ones own descriptor terms as opposed to a classification performed by another person. The fourth group of 10 subjects classified objects using a vocabulary supplied by the experimenter; they assigned many more terms to each object. There are tentative indications that some individuals differ from others in the structure of the classifications they construct These results suggest that it is helpful to allow people to classify materials for their own use, that they would benefit fr...

Performance effects of diazepam during and after prolonged administration.

Seven volunteers received diazepam for a 3-week period, maximum dose rate 25 mg per day, and were tested on a variety of functions before, at two points during, and at two points after the period. Their performance was compared with that of 8 controls and was inferior on a number of measures. There was no indication either of habituation or of potentiation of the effects as the period continued. Equally, the low performance persisted for some time after administration ceased, although performance was on the whole better than during the experimental period. The particular measures showing deterioration suggested that the effects are similar to those of barbiturates as opposed to those of, for example, chlorpromazine.

Encoding Speed of Visual Features and the Occurrence of Illusory Conjunctions

Earlier studies have found that people show characteristic errors when asked to observe a rapid stream of events and to name the colour of a certain letter, or the letter in a certain colour. They tend to report the letter or colour from an event later in time than the correct one. This is not true, however, if they are asked to name the colour of a digit amongst letters, without knowing in advance the identity of the digit. There is also some evidence that the errors are symmetric if the location of the target is not known in advance. Three experiments are reported which show that this symmetry results from slow encoding of the colour as compared with the digit. It is still true that uncertainty about target identity does reduce the tendency to see the target in a later rather than an earlier colour. This effect is, however, superimposed on asymmetries resulting from coding speed, and the effect of uncertainty of location may be due only to this.