Comparative evaluation of computer-based tachistoscopes

Various methods of implementing a computer-based tachistoscope are compared. Software considerations are emphasized, but hardward issues are also examined. Three types of systems are identified: file-driven systems, sets of callable subroutines, and special languages. All have advantages in some circumstances. A system of callable subroutines is favored, together with a file-driven system written in the host language using the subroutines.     

Introduction

A series of eight papers is introduced on methods of using a computer system as a tachistoscope. Comparisons are based on the type of display and the type of software.     

Signal detection and identification at successive stages of observation

The relationship of signal identification to signal detection was examined in a series of experiments. The signals were idealized lines and patterns of lines in a spectrographic display. On each trial, progressively more of the complete spectrogram was exposed in successive observation intervals, and after each interval the observer made both detection and identification responses that were based on the accumulating evidence. One model we employed conceives of detection and identification as proceeding together over time as parts of a unified process. A second model used shows how thejoint detection-and-identification ROC—a relative operating characteristic that relates the joint probability of correct detectionand correct identification to the probability of a false detection—may be predicted from the simple detection ROC. Both models were supported by the data.     

The Rawdon-Smith illusion

A loudness illusion is described which was originally reported by Rawdon-Smith and Grindley (1935). It is analogous to the Craik-O’Brien-Cornsweet brightness illusion. Procedures are described for generating and measuring the size of the effect, and data are presented showing factors that influence its magnitude. Other examples are discussed that suggest that this effect is a very general phenomenon.     

The effects of context and content on immediate processing in reading

Four experiments were conducted to examine the processes by which fluent readers comprehend prose. In each study the material was presented a few words at a time on an on-line visual display and the subject pressed a button to move on from one display to the next. The inter-reponse time was used as an index of local processing difficulty. The results of Experiment I indicated that readers pause considerably at the ends of clauses and sentences, and that they show no tendency to speed up across sentences. This pattern of results questions the role of prediction in reading. In Experiments II and III immediate processing was found to be unaffected by two types of syntactically-predictive clue and the effect of a third (semantic) clue was equivocal. Experiment IV replicated the results of Experiment I and showed, in addition, that pausing at the ends of clauses and sentences is a function of the difficulty of the content of the text. More detailed analyses showed that reading rate is modulated by the frequency of the words and by the number of characters in the display. Taken together the results suggest that reading rate is largely determined by the speed with which a reader can access the meanings of words and construct a representation of the text rather than by the speed with which they can formulate and test successive predictions about it.     

Interference effects in an auditory Stroop task: congruence and correspondence

Two auditory Stroop experiments are reported in which subjects responded vocally to the gender of the speaker of stimulus words. The interference effects found were broadly similar to those of a manual-response auditory Stroop paradigm although response-set effects appeared to operate in the data. In all experimental conditions responses were slower to stimulus words which named potential responses than to those words which did not. Such effects have not been found in previous manual-response experiments and it is suggested that the relatively high degree of S-R and of ideomotor compatibility in the vocal response task, compared with the manual task, may be responsible for this difference between the paradigms.The second experiment enabled a comparison to be made between the effects of congruence between relevant and irrelevant elements of the Stroop stimulus and the effects of correspondence between the response and the irrelevant aspect of the stimulus. A predominant influence of congruence was found when the subject responded using words semantically related to speaker gender, but an effect of correspondence was obtained when an arbitrary pairing of response word and speaker gender was required.     

What did I eat yesterday? Determinants of accuracy in 24-hour food memories

Large-scale diet-related epidemiological work relies on the quality of self-reported food consumption. As this epidemiological work forms the basis of knowledge of the relationship of diet to disease, it is essential that the self-reports of personal diet are understood. It is generally accepted that foods consumed are under-reported, even over as short a period as 24 hours. However, little is known about the potential systematic biases that may affect the quality of self-reported food intake. The current study examines the accuracy of memories of the consumption of snack foods eaten in the previous 24 hours and investigates factors that may bias these memories. All participants had previously participated in a randomized intervention trial to lower dietary fat intake to 20 per cent of calories. Fifty-six women (intervention and control) tasted eight snack foods in a laboratory setting. They were telephoned a day later and asked to recall the type of snack foods (M&Ms, pretzels, etc.) and the quantity of each food they consumed. Subjects in general under-reported the number of selections and the quantity of each item consumed. Women who accurately recalled an item, reported more liking for that item compared to those who forgot the item. Women currently maintaining a low-fat diet were less accurate in their recall of low-fat items than women on a high-fat diet. Low-fat eaters, however, may be slightly better at recalling how much of certain foods they consumed. Results have implications for survey research and understanding the psychological influences on reports of food consumption used in large-scale diet studies.