Development of strategies for recalling letter sequences

Kindergarten, second-grade, and fourth-grade children (6, 8, and 10 years of age, respectively) were asked to recall letter sequences on a task that required the use of: (a) a verbal strategy; (b) a positional strategy; or (c) either strategy. Additional trials, allowing either strategy, were interspersed among those requiring a verbal or positional strategy; strategy use was determined from performance on these interspersed trials. The results show that children at all grade levels attempted to use a task-appropriate strategy. Performance on the verbal task showed a more marked developmental increase than did performance on the positional task. A second experiment replicated the first with the interspersed trials removed. A third experiment was designed to determine whether letter names interfered with older children's efficient use of a positional strategy. Even with this source of interference removed, the developmental pattern of Experiments 1 and 2 was replicated. There was a Sex by Condition interaction in Experiments 2 and 3 which showed that males do better in the condition requiring a positional strategy, and females do better in the condition requiring a verbal strategy.     

Keeping it short: a comparison of methods for brief picture presentation

Abstract— Research has shown that backward masking is a powerful tool for studying unconscious mental processes. Whereas studies have traditionally presented stimuli using cathode-ray tube (CRT) monitors or mechanical shutters together with slide projectors, recent studies (mainly in functional magnetic resonance imaging, fMRI) have begun to use methods based on liquid crystal displays (LCDs) and thin-film transistor (TFT) technology. However, because of differences in technology, all methods may not be equally suited for masking. When methods were compared for their accuracy in presenting pictures at short durations, LCD and TFT presentations had poor accuracy, but shutter and CRT presentations had better accuracy. Because CRTs interfere with the imaging process in fMRI, we recommend the use of mechanical shutters. However, our results may not generally apply to all displays, so we advise researchers to validate the presentation parameters of their displays. The procedure described here may be useful for that purpose.     

Identification of tachistoscopically exposed symmetrical and asymmetrical letter arrays.

Six-letter arrays containing symmetrical, e.g., H, M, T, or asymmetrical letters, e.g., J, K, R, were tachistoscopically exposed bilaterally for 100 msec. to 100 college students. Significantly more asymmetrical than symmetrical letters were identified, and significantly more Ss identified more asymmetrical than symmetrical items. This experiment, which incorporated methodological considerations suggested by Harcum (1964) and Bryden (1968), corroborates their findings. Their ideas and other findings were used to account for the data. Asymmetrical letters have more intrinsic left-to-right directionality than symmetrical elements. The rapidly fading after-stimulation of tachistoscopically presented alphabetical material is usually scanned from left to right. Individual array letters might also be scanned in the same direction. Confluence of directionality of letter and scan, which obtains only with asymmetrical letters, might have typically allowed asymmetrical targets to be scanned more rapidly and, consequently, more efficiently than symmetrical displays.     

Extracting identity and location information from briefly presented letter arrays

The effect on identification and location of briefly presented targets (letters and blanks) of number of targets, retinal location, and direction and distance of simultaneously presented targets is investigated. In three different conditions, one, two, or three targets are presented on a trial with the location of targets varying from trial to trial. A model is proposed to describe identification and location performance in the one-letter condition. This model distinguishes between two sets of parameters, perceptual parameters and decision parameters, and assumes that in terms of these parameters, identification and location are independent processes. The perceptual and decision parameters of the model, estimated by assuming that these parameters are linearly related to retinal location, indicate that retinal location has a different effect on the decision parameters for both identification and location than on the perceptual parameters. Variables affecting the performance decrements found when multiple letters are presented are evaluated in terms of models stated for the multiple letter conditions. Estimates of the effects of distance from the fixation point and inter-letter distance indicate that, as both of these variables increase, performance decreases. In the three-letter condition, a serial position effect is found, with performance on center letters being relatively poor. A peripherally presented letter is found to have a large detrimental effect on performance, and the effect increases as interletter distance increases. Location of correctly identified targets follows many of the same patterns as identification performance in the multiple letter conditions. In addition, there is a tendency for incorrectly located targets to be moved foveally and to move to positions occupied by other targets on the trial. The possibility of a limited-capacity attention mechanism operating in the present experiment is discussed.     

A matched-subject comparison of underachievers with normals on intellectual,behavioral, and emotional variables

Children labeled as under achievers are compared to a matched group functioning normally within the classroom. Factor analyses of the data from several tests reveal that the normal children not only have achieved higher academic performance but also have better learning aptitude. The inference may be made that many underachievers actually have a low general aptitude when carefully measured.This study was supported from funds from the Holden Foundation at the Children's Hospital of Michigan. The authors extend their thanks to Mrs. Barrie Lowy, Mrs. Sheila Kempler, and Ms. Enid Braun.     

Tactile letter recognition under different modes of stimulus presentation

Block capital letters were displayed to experienced and inexperienced Ss, using a 20 x 20 matrix of vibratory tactors placed against the back. In two separate experiments, a total of five modes of stimulus presentation, three of them employing a linear scanning slit, were studied. The poorest method, stationary flashing of the letter, allows performance that is well above chance, implying that a purely spatial presentation does convey information. Performance is improved when the letter is moved horizontally across the display. The best performance is achieved when the amount of simultaneous stimulation is limited by using a linear scanning slit. In one method, the letter moves behind a stationary slit, with the result that its horizontal dimension is portrayed only in time. In the other two methods, the scanning slit moves across the stationary letter, portraying the letter both in time and in space. The results of all five display modes indicate that Ss can use whichever representation, spatial or temporal, is available, although patternings which most closely approximate sequential tracing by a single moving point lead to the highest recognition accuracy. We interpret these results in terms of the limited spatial resolution of the cutaneous sense. While the perception of a letter presented in either full-field condition is limited by the spatial resolution, the best measure being the two-point limen, the perception of a letter traced sequentially is limited by the localization acuity of the cutaneous sense, the best measure being the “error of localization,” which is known to be considerably smaller than the two-point limen. Inasmuch as the slit methods of presentation are a compromise between simultaneous and sequential display, letter-recognition accuracy is better with slit presentation than with the corresponding full-field mode of display.     

A comparison of presentation methods of video identification parades

Researchers have demonstrated that sequential lineup presentation reduces false identifications from perpetrator absent lineups. In England and Wales police identification parades are shown on video in a sequential manner. However, police sequential presentation varies from the strict sequential presentation advocated by researchers. In addition, after police have shown the sequential presentation they also have the option to show witnesses a matrix of the parade where witnesses can see all members of the parade simultaneously. The research reported investigated the effect of strict sequential presentation, police sequential presentation and police sequential presentation plus matrix on mock witnesses' performance on perpetrator present and absent video identification parades. Strict sequential presentation led to fewer correct identifications of the perpetrator than police sequential and police sequential plus matrix, with no difference in performance between either of the police conditions. For perpetrator absent lineups there was no effect of lineup presentation condition on lineup performance. Copyright © 2010 John Wiley & Sons, Ltd.     

Knowledge of the alphabet: A comparison between letter counts and subjective reports

Subjects’ estimates of the frequency of occurrence of the letters of the alphabet were compared with previously reported letter-frequency counts. The results indicated an overall good relationship between actual and judged rank, but there were consistent letter-specific under- and overestimations. These inaccuracies were not accounted for by letter versatility, first-position frequency, or order in the alphabet. There was evidence that subject-derived estimates of letter frequency were somewhat better predictors of reaction time performance on letter-processing tasks.     

Impaired oral reading in two atypical dyslexics: a comparison with a computational lexical-analogy model

A computational model of reading was developed based upon the notion that the structural relationship between orthography and phonology is of greater importance than the dimension of semantics for the reading aloud of single words. Degradation of this model successfully simulated the reading performance of two patients with atypical acquired dyslexia. The first patient CAV, studied and described in the literature by Warrington in 1981, presented with unusual concrete word dyslexia, i.e., he had a category-specific reading deficit for concrete words compared with abstract words. The second patient BG is a phonological dyslexic who, although displaying a strong concreteness effect (concrete words read better than abstract words), was able to read functors individually perfectly well, a pattern that is rarely if ever seen. The computational model was used to generate a set of words for which it was predicted that BG would show no concreteness effect. The results of BG's reading of these words were consistent with this prediction, thereby providing greater support for the validity of the model. It is concluded that a computational approach that attempts not only to reproduce the core symptoms of the major varieties of acquired dyslexia but also to simulate clinical data from specific patients has much to contribute to the understanding of cognitive deficits and to the design of effective rehabilitation strategies.     

A comparison of Nuk presentation and Nuk redistribution to treat packing

Children with feeding disorders may pack food when they lack the oral‐motor skills, the motivation, or both to swallow. Presenting bites on the tongue with a Nuk brush, or redistribution, replacing packed food on the tongue, are two treatments whose relative efficacy is untested. In the current study, we compared the effects of (a) presenting on an upright spoon, (b) presenting on a Nuk, and (c) redistributing with a Nuk on two product measures of swallowing, which we refer to as 15‐s and 30‐s mouth clean, for three children with feeding disorders. Nuk presentation produced the highest levels of 15‐s mouth clean relative to Nuk redistribution and upright‐spoon presentation across participants. Levels of 30‐s mouth clean were higher during Nuk presentation and Nuk redistribution relative to upright‐spoon presentation for two participants. We discuss the oral‐motor skills and motivational deficits that might account for the findings.