The influence of word-knowledge on the word-frequency effect in recognition memoryThe signal detection theory technique of using ope rating characteristics (OCs) in the study of recognition memory is derived from S's confidence ratings made to a test sequence of words containing both initial inspection and additional items (see, for example, Green & swets, 1966, for details). This method provides a graphic estimate, ds , of the degree of difficulty in discriminating new from old words. As part of one such application of this technique, Schulman (1967) has demonstrated that rare words (Thorndike-Lorge frequency 1) were easier than very common words (Thorndike-Lorge frequency of A or AA) to identify as old or new; but, as Schulman has noted, the rare words used in his experiment were by no means unfamiliar ones. The experiment reported here uses OCs in an attempt to separate the effects of rarity defined in terms of the S's inability to define the meaning of a word. This is achieved by asseSSing the recognition performance of two groups of Ss, physics and arts students, on a sequence of test words containing both technical physics words and common words. In such a situation a physics word, e.g., "tetrode," is rare (low word count) for both physics and arts Ss, yet its meaning is likely to be rare (word knowledge) only for arts Ss.In order to demonstrate a word-frequency effect as reported by Schulman, the OC curves of both physics and arts Ss would be expected to indicate that physics words, rather than common words, were easier to differentiate as being either old or new. In order to demonstrate a word-knowledge effect, significant differences would be expected in the OC curves of physics and arts Ss for physiCS words but not for common words. The superior discrimination of physics words by physics Ss would suggest that a knowledge of word meaning facilitates recognition while a superior performance by arts Ss on physics words would suggest that their rarity aided discrimination as in the wordfrequency effect. The Ss, tested in small groups, were 50 university students, 25 having completed at least one year of an honors physics course and 25 honors arts Ss having little if any science training at high school.An inspection sequence of 60 words contained 30 common words (Thorndike-Lorge rating of300rmore), and 30 physics words. The latter were chosen in order that they would be very familiar to second year university students enrolled for a major in physics while at the same time they would not be a part of the arts Ss ordinary vocabulary. Each word was projected onto a screen for 3 sec using a Kodak Carousel automatic projector (Model 550R) with a 0.5 sec interval between words. The Ss were instructed to try to remember the words appearing on the screen. There was a 3 min interval between the completion of the inspection task and the start of the recognition test. A recognition booklet contained 120 words in random order: 60 physics and 60 common words including all the inspection items.! The Ss marked these words...

Base-rate neglect is a failure to sufficiently bias decisions toward a priori more likely options. Given cognitive and neurocognitive model-based evidence indicating that, in speeded choice tasks, (1) age-related slowing is associated with higher and less flexible overall evidence thresholds (response caution) and (2) gains in speed and accuracy in relation to base-rate bias require flexible control of choice-specific evidence thresholds (response bias), it was hypothesised that base-rate neglect might increase with age due to compromised flexibility of response bias. We administered a computer-based perceptual discrimination task to 20 healthy older (63-78 years) and 20 younger (18-28 years) adults where base-rate direction was either variable or constant over trials and so required more or less flexible bias control. Using an evidence accumulation model of response times and accuracy (specifically, the Linear Ballistic Accumulator model; Brown & Heathcote, 2008), age-related slowing was attributable to higher response caution, and gains in speed and accuracy per base-rate bias were attributable to response bias. Both age groups were less biased than required to achieve optimal accuracy, and more so when base-rate direction changed frequently. However, bias was closer to optimal among older than younger participants, especially when base-rate direction was constant. We conclude that older participants performed better than younger participants because of their greater emphasis on accuracy, and that, by making greater absolute and equivalent relative adjustments of evidence thresholds in relation to base-rate bias, flexibility of bias control is at most only slightly compromised with age.

Deciding not to choose 1We propose a dynamic theory of decisions not to choose which of two options is correct. Such "don't-know" judgements are of theoretical and practical importance in domains ranging from comparative psychology, psychophysics, episodic memory and metacognition to applied areas including educational testing and eyewitness testimony. However, no previous theory has provided a detailed quantitative account of the time it takes to make both definitive and don'tknow responses and their relative frequencies. We tested our theory, the "Multiple Threshold Race" (MTR), in one recognition memory experiment where participants had to pick a previously studied target out of two similar faces and another where targets and lures were tested one at a time. In both experiments we manipulated similarity through face morphing. High similarity made decisions difficult, encouraging don't-know responses. We also tested the MTR's ability to account for other manipulations that aimed to affect the speed and probability of don'tknow responses, including increasing penalties for making an error (with no penalty for a don'tknow response) and emphasising either response speed or accuracy. We found that there were marked individual differences in don't-know use, and that the MTR was able to account for the intricate pattern of effects associated with our manipulations, both on average and in terms of individual differences. We discuss how estimates of MTR's parameters illuminate the psychological mechanisms that govern the interplay between definitive and don't-know responding.

We propose a dynamic theory of decisions not to choose between two options. Such “don’t-know” judgements are of theoretical and practical importance in domains ranging from comparative psychology, psychophysics, episodic memory and metacognition to applied areas including educational testing and eyewitness testimony. However, no previous theory has provided a general account of both the time it takes to make both definitive and don't-know responses and their relative frequencies. We tested our theory, the “Multiple Threshold Race” (MTR), in one recognition memory experiments where participants had to pick a previously studied target out of two similar faces and another where targets and lures were tested one at a time. High similarity made decisions difficult, encouraging don't-know responses, and we manipulated similarity through face morphing. We also tested the MTR’s ability to account for other manipulations that aimed to affect the speed and probability of don't-know responses, including increasing penalties for making an error (with no penalty for a don't-know response) and emphasising either response speed or accuracy. We found that there were marked individual differences in don't-know use, and that the MTR was able to provide a detailed account of the intricate pattern of effects associated with our manipulations, both on average and in terms of individual differences. We discuss how estimates of MTR’s parameters illuminate the psychological mechanisms that govern the interplay between definitive and don't-know responding.

Word recognition was examined for physics and non-physics students after a single visual presentation of a series of sixty words. Physics words likely to be familiar only to physics subjects were used to vary the prior familiarity of the two groups with the inspection material and the ratio of physics to common words (salience) was varied for each of the three inspection series. Common words, which were expected to have greater salience than physics words in one of the inspection series, were not found to be recognized better than the control pairings of physics words by either group of subjects. The absence of differences between physics and non-physics students in the number of inspection list words (positive instances) correctly identified supports the view that prior familiarity is not a critical variable when all inspection items are presented in a recognition test. Physics students made fewer errors than non-physics students in identifying both physics and common words in the the recognition test which were not in an inspection series (negative instances). It is suggested that the correct identification of negative instances involves a scanning of a subject's “internal store” of previously experienced inspection items and that this is more efficient when the meaning of all the items in this “store” is known.