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PubMed2002

Preneural limitations on letter identification in central and peripheral vision.

We created a sequential ideal-observer model that could address the question, How much of letter identification performance and its change with eccentricity can be accounted for by preneural factors? The ideal-observer model takes into account preneural factors including the stimulus rendering properties of a CRT display, the optical imaging quality of the eye, and photon capture and sampling characteristics of the cones. We validated the formulation of the model by comparing its performance on simple psychophysical tasks with that of previous sequential ideal-observer models. The model was used to study properties of the image rendering of letters. For example, the model's identification of high-resolution letters (i.e., many pixels per letter), but not low-resolution letters, is largely immune to changes in pixel width. We compared human and ideal-observer letter-identification acuity for the lowercase alphabet at 0 degrees, 5 degrees, and 20 retinal eccentricity. Acuity of the ideal observer for high-contrast letters is approximately seven times better than that of the human observers at 0 degrees. Acuity decreased with eccentricity more rapidly for human observers than for the ideal observer such that the thresholds differed by a factor of 50 at 20 degrees. A decrease in stimulus duration from 100 to 33 ms resulted in no decrease in relative threshold size between the human and ideal observers at all eccentricities, indicating that humans effectively integrate stimulus information over this range. Decreasing contrast from 75% to 25%, however, reduced the difference in acuities twofold at all eccentricities between humans and the ideal-observer model, consistent with the presence a compressive nonlinearity only in the human observers. The gap between human and ideal acuity in central vision means that there are substantial limitations in human letter recognition beyond the stage of photoreceptor sampling. The increasing performance gap between human and ideal-observer performance with eccentricity implicates an increasing role of neural limitations with eccentricity in limiting human letter identification.

Adult↗

PubMed2004

Effect of periodic letters on evidence-based drug therapy on prescribing behaviour: a randomized trial.

BACKGROUND: The effect of regular and expected printed educational materials on physician prescribing behaviour has not been studied. We sought to measure the impact of a series of evidence-based drug therapy letters mailed to physicians in British Columbia on prescribing to newly treated patients. METHODS: A paired, cluster randomized community design was used. The study population included 499 physicians from 24 local health areas in British Columbia. Local health areas were paired by number of physicians, and 1 of each pair was randomly selected and its physicians assigned to an intervention group or a control group. The intervention was 12 issues of an evidence-based series called Therapeutics Letter. Physicians in the control group (n = 241) received the letters 3-8 months after physicians in the intervention group (n = 258). The impact on prescribing to newly treated patients (defined as patients who had not previously made a claim for any medication from the class of drugs profiled in the letter) was analyzed using the drug claims database of BC Pharmacare, a publicly funded drug benefits program that covered all seniors and people receiving social assistance. RESULTS: The probability of prescribing a drug recommended in the Therapeutics Letter rather than another drug in the same class increased by 30% in the 3 months after the mailing of the letter relative to the preceding 3 months, adjusted for any before-after changes in the control group (relative risk 1.30; 95% confidence interval 1.13-1.52). No letter achieved statistical significance on its own. However, 11 of the 12 letters produced prescribing changes in the predicted direction such that the overall result was significant when their effect was combined. INTERPRETATION: The combined effect of an ongoing series of printed letters distributed from a credible and trusted source can have a clinically significant effect on prescribing to newly treated patients.

Adult↗

PubMed1998

Abortion affiliation, urban size, and geographic bias of responses to lost letters.

A study using 1800 "lost letters" was designed to test the hypothesis that returned responses would be greater in smaller rural communities (population M = 964) than in a city (population = 60,591) or the suburbs (population = 195,847) unless the addressee was affiliated with a pro-abortion group. Returns to control, Committee For Free Abortion, and Committee Against Free Abortion affiliates were 37.2%, 24.0%, 29.3%, respectively. From the city, the number of returned letters was much larger than the number from the suburbs except for those letters with an affiliation to the pro-abortion condition. Returned letters from the city were fewer than those from smaller rural communities except those letters affiliated with the pro-abortion group. More letters affiliated with the pro-abortion condition were returned from the suburbs than from the smaller rural communities. The geographic condition influenced over-all rates of return. Rates were higher when letters were addressed to a city P.O. Box than to a rural one. Second, rates were also greater in smaller rural communities for letters bearing "in-town" (Molino) and "out-of-town" (Pensacola) addresses than those from the city bearing an "out-of-town" (Molino) address. These findings seem to indicate the possibility that there may be some geographic bias in the willingness of people to help a stranger in need by returning a lost letter.

Abortion, Legal↗

PubMed2003

Letter visibility and the viewing position effect in visual word recognition.

The ease with which printed words are recognized depends on the position at which the eyes initially fixate the word. In this study, we examined to what extent recognition performance for each fixation position depends on the average visibility of the word's constituent letters. Experiment 1 measured recognition performance to single letters embedded in strings of Xs (lengths of 5 and 7) for all combinations of letter position and initial fixation position in the string. In Experiment 2, recognition performance was measured for five-letter and seven-letter words as a function of initial fixation position in the word. Whereas average letter visibility showed a symmetric function in Experiment 1, the word recognition data of Experiment 2 showed the typical asymmetric curve. Combining the letter visibility data with measures of lexical constraint using absolute letter-in-string positions failed to capture the pattern in the word data. An alternative measure of constraint based on relative position coding of letters generated more accurate predictions.

Adult↗

PubMedDate not supplied

A comparison of two computer input devices for uppercase letter matching.

OBJECTIVE: To determine whether the Touch Window or the mouse with an enlarged on-screen arrow was more effective or efficient for an on-screen letter-matching task completed by a boy 9 years of age with spastic quadriplegic cerebral palsy and visual and cognitive deficits. METHOD: A single-subject research design of 5 treatment phases, A1, B1, A2, B2, and A & B, was used. The total percentage of correct letter matches per treatment session, the total percentage correct per letter, and the amount of time needed to match 5 consecutive letters correctly were evaluated. RESULTS: The range and variability of letters correctly matched per session decreased and trends for correct letter matches accelerated when the participant used the mouse interface. Accuracy with matching 18 of 26 (69%) letters of the alphabet increased when selections were made with the mouse interface. The participant was faster when using the Touch Window to match 5 consecutive letters correctly; however, regardless of the interface device used, letter matching remained slow and tedious. CONCLUSION: The mouse with an enlarged on-screen arrow and cursor was the more effective interface device with this child. Making a minor adjustment such as increasing the size of the on-screen arrow can make a common piece of equipment accessible to a person with disabilities.

Cerebral Palsy↗

PubMed2002

Improving doctors' letters.

Information contained in letters of referral and reply often does not meet the information needs of letter recipients. Missing reports of previous investigations and insufficient detail in the referral letter to specialists are the most serious and common problems. General practitioners prefer structured, computer-generated letters to unstructured, dictated letters. Referring surgeons and GPs identify delay in receiving the reply letter and insufficient detail as relatively common problems after a new patient consultation. They want the reply letter to describe the proposed treatment, expected outcomes and any psychosocial concerns, yet these items are often omitted. A letter content and format prompt card has the potential to enhance the quality of correspondence between medical specialists and referring doctors. Specialist medical bodies should consider preparing prompt cards (setting out preferred information content and format for letters) to distribute to their members.

Correspondence as Topic↗

PubMed1976

Repetition and acoustic contrast in short-term memory for letter sequences.

Memory for sequences of briefly presented letters was examined to discover the effects of intraserial repetition and acoustic contrast on recall of a critical letter pair. The critical pairs were either repeated or nonrepeated letters presented in an acoustically contrasting or noncontrasting sequence. The hypothesis was tested that recall of repeated letters and contrasting nonrepeated letter pairs would depend on the lag between their presentations. Immediate recall of both letters (but not recall of at least one letter) of a critical pair was enhanced when the pair was a repetition or acoustically contrasting but only when the letters of the pair were adjacent. Recall of pairs separated by a lag of two intervening letters was not affected by repetition or contrast. When recall was delayed by a retention interval of eight random digits, the contrast effects disappeared and only the repetition effect remained. The findings are discussed in terms of the coding of attribute tags as cues for retrieval from short-term memory.

Auditory Perception↗

PubMed2005

A study of business letter features.

As part of their work, forensic document examiners examine word processed letters. The purpose of this study, the first of its kind, was to determine how common or rare certain features are in word-processed business letters and if any of these features could determine the author or source. Initially, 114 original business letters were obtained that were dated from 1999 through 2003. Specific features of the letters were selected for examination. These features were letter format, type style, the point size of the font, margin spacing to ascertain the use or nonuse of the default margins for Word (1.25 in. nonjustified) and the default margins for WordPerfect (1 in. nonjustified). In addition, the research involved the examination of the right margins to determine if they were justified or not and the use of the comma or colon in the salutation of the letter. The features of each letter were independently examined by the authors and the findings documented. As expected, several features were found to be very common. For example,full block format was used on 48% of the letters followed by the semi-block with 39%. The Times Family of fonts was used on 67% of the letters. Font point size 12 was the most popular with 70%. The nonjustified default margins were widespread with 67% and the colon was the overwhelming favorite in the salutation with 79%. There were some unexpected findings that could possibly lead to the identification of a source or typist.

Journal Article↗

PubMed2006

General practitioners' referral letters--Do they meet the expectations of gastroenterologists and rheumatologists?

OBJECTIVE: To solicit the views of gastroenterologists and rheumatologists on the importance of various aspects of general practitioners' referral letters, and to assess GPs' letters based on these views. METHODS: Questionnaires were sent to 175 gastroenterologists and 88 rheumatologists in New South Wales to seek their views on the importance of nine items in GPs' letters. Four hundred referral letters from GPs were audited based on these items. RESULTS: Gastroenterologists and rheumatologists held very similar views on the importance of various aspects of GPs' letters. Most GPs' letters were legible and contained reason for referral, past medical history and current medications. Only a minority of letters contained family history, social history, physical findings, and prereferral investigation results. DISCUSSION: General practitioners' referral letters measured up well to some expectations of gastroenterologists and rheumatologists, but often failed to include some important information. The use of structured form letters is recommended.

Correspondence as Topic↗

PubMed1990

Letter identification and lateral masking in dyslexic and average readers.

Lateral masking and letter identification in dyslexic and average readers were investigated with a methodology that corrected for some of the weaknesses of the Geiger and Lettvin studies (1986, 1987). Target letters were presented alone or embedded within three-letter arrays at retinal locations from 0 degrees to 15 degrees to the right or left of a fixation point. A foveal letter, which was the same as or different from a target letter, appeared as a distractor, and comparisons were made between scaled and unscaled stimuli. Dyslexic readers were found to be better than average readers at detecting scaled letters embedded in an array in some of the peripheral locations tested. Unlike the results of Geiger and Lettvin, however, this finding of better letter detection in the periphery by dyslexics was limited to selected conditions of the study. Reading groups were also found to differ in responding to the foveal distractor in the letter task. Detection of letters by average readers was affected by the type of distractor, but this variable was not found to influence the dyslexic readers. These findings suggest some differences between dyslexic and average readers in attention to stimuli presented at multiple locations in the visual field.

Adult↗

PubMed1979

Search for structures involved in integration of letters in pairs.

Two experiments aimed at finding, at what stage of perceptual processing the positive interactions between letters, observed in some previous studies, are established. Single letters and pairs of letters were exposed. The task of the subjects was to recognize letters. In Experiment I bright letters on a black background were used instead of black letters on bright background used in previous experiments. Such change of brightness within the stimuli did not influence the character of interactions between letters. This suggests that the positive interactions are connected with higher level of visual system. In Experiment II patients with damage of various areas of the brain cortex were tested. The facilitation between two letters did not occur in patients with prestriate lesions, although it can be observed in patients with different localization of lesions. This suggests that prestriate cortex is involved in positive interactions between letters.

Cerebral Cortex↗

PubMed1997

The Fragility of the Alphabetic Principle: Children's Knowledge of Letter Names Can Cause Them to Spell Syllabically Rather Than Alphabetically

The present research was designed to investigate how children's early-acquired knowledge of letter names affects their spelling. Specifically, we asked whether kindergartners and first graders sometimes spell a sequence of phonemes such as /bi/ (the name of the letter b) or /zi/ (the name of the letter z) with the corresponding consonant letter rather than spelling the sequence alphabetically, with a consonant letter followed by a vowel letter. Children made a number of letter-name spelling errors, especially when the consonant and vowel formed a complete syllable. These results show that children's knowledge of letter names can cause them to deviate from the alphabetic principle-the principle that each phoneme should be represented with a single grapheme. The findings further suggest that syllables play a special role in early writing.

Journal Article↗

PubMed1991

Target--distractor separation and feature integration in visual attention to letters.

The interference produced by distractor letters diminishes with increasing distance from a target letter, as if the distractors fall outside an attentional spotlight focussed on the target (Eriksen and Eriksen 1974). We examine Hagenaar and Van der Heijden's (1986) claim that this distance effect is an acuity artefact. Feature integration theory (Treisman 1986) predicts that even when acuity is controlled for, distance effects should be found when interference is produced by conjoined distractor features (e.g. letter-identities), but not when interference arises from isolated distractor features (e.g. letter-strokes). The opposite pattern of results is found. A model is proposed in which both letter-strokes and letter-identities are derived in parallel. The location of letter-strokes can also be coded in parallel, but locating letter-identities may require the operation of attention.

Attention↗

PubMed1993

Does the production of letter strokes in handwriting benefit from vision?

In earlier studies the involvement of vision in handwriting was suggested by the finding that the production of a letter sequence in a condition without vision took more time and resulted in larger letter trajectories. The present study raises the question whether vision has an impact on the production of the individual up- and downstrokes constituting the letters. More specifically, the aim is to examine whether vision is employed either during the completion of a movement, or concurrent with the entire course of a stroke movement. Adult writers produced the letter sequence lelele under a no-vision and a vision condition, the latter serving as a base-line condition. It was found that movement time and trajectory size of acceleration and deceleration phases of a stroke movement increased under no vision, the magnitude of which depended on letter type. Letter e, with a smaller size and more frequently used in Dutch writing than letter l, was less affected by the no-vision condition. Although, close examination of downstrokes produced in later letter positions of the sequence revealed that the acceleration as compared to the deceleration phase took proportionally less time, the general finding was that increments in time and size proved to be equally distributed across entire stroke movements.

Adult↗

PubMed1994

Reading of letters and words in a patient with Balint's syndrome.

A patient with bilateral parietal damage, and Balint's syndrome, named visual letters. These were presented individually or within four-letter strings. Solitary letters were identified very accurately. In the case of strings, more letters were correctly reported for words than for nonwords, and more for pronounceable than for unpronounceable nonwords. When required to read words as a whole, performance was better than predicted by letter-reports. These results extend the object-based limitation apparent in Balint's syndrome to the case of reading. The component letters of a string benefit when they form a familiar global object, rather than requiring representation as multiple separate objects. The patient occasionally made homophonic errors when listing the letters in a visual word. This suggests an attempt to bypass visual simultanagnosia by treating the string as a single object, deriving a holistic phonological code for it, and then decomposing this into component letters via spelling rules.

Agnosia↗

PubMed1987

Effects of concurrent spatial and verbal memory loads on serial position functions of laterally presented letter strings.

In this study the influence of visuospatial and verbal memory loads on the identification of laterally presented letter strings was investigated. In the asymmetry task without concurrent loads, a clear right visual field advantage for letter identification was obtained. Hemisphere-specific effects due to concurrent loads were particularly observed when the difficulty of the load tasks was increased. The effects of visuospatial loads were found to be sex related, suggesting that under heavy load conditions mental rotation selectively overloads the processing capacity of the right hemisphere in males, while in females capacity limitations were observed in both hemispheres. Concurrent visuospatial loads produced more facilitation (or less interference) for letters in the outermost positions of each visual field than for letters in the innermost positions of each visual field. The results of the verbal memory load tasks revealed that an easy verbal load task facilitated performance which was particularly manifest for the right-most letter of both the left visual field and the right visual field. A difficult verbal memory load task interfered with recognition accuracy of letters which was most marked for the center letter in the right visual field. Letter position effects obtained in this study were interpreted in terms of various processing mechanisms influencing the serial position curves.

Adult↗

PubMed2005

Transposed-letter and laterality effects in lexical decision.

Two divided visual field lexical decision experiments were conducted to examine the role of the cerebral hemispheres in transposed-letter similarity effects. In Experiment 1, we created two types of nonwords: nonadjacent transposed-letter nonwords (TRADEGIA; the base word was TRAGEDIA, the Spanish for TRAGEDY) and two-letter different nonwords (orthographic controls: TRATEPIA). In Experiment 2, the controls were one-letter different nonwords (TRAGEPIA) instead of two-letter different nonwords (TRATEPIA). The effect of transposed-letter similarity was substantially greater in the right visual field (left hemisphere) than in the left visual field. Furthermore, nonwords created by transposing two letters were more competitive than the nonwords created by substituting one or two letters of a target word. We examine the implications of these findings for the models of visual word recognition.

Brain↗

PubMed2007

Do transposed-letter similarity effects occur at a morpheme level? Evidence for morpho-orthographic decomposition.

When does morphological decomposition occur in visual word recognition? An increasing body of evidence suggests the presence of early morphological processing. The present work investigates this issue via an orthographic similarity manipulation. Three masked priming lexical decision experiments were conducted to examine the transposed-letter similarity effect (e.g., jugde facilitates JUDGE more than the control jupbe) in polymorphemic and monomorphemic words. If morphological decomposition occurs at early stages of visual word recognition, we would expect an interaction with transposed-letter effects. Experiment 1 was carried out in Basque, which is an agglutinative language. The nonword primes were created by transposing two letters that either crossed the morphological boundaries of suffixes or did not. Results showed a transposed-letter effect for non-affixed words, whereas there were no signs of a transposed-letter effect across morpheme boundaries for affixed words. In Experiment 2, this issue was revisited in a non-agglutinative language (Spanish), with prefixed and suffixed word pairs. Again, results showed a significant transposed-letter effect for non-affixed words, whereas there were no signs of a transposed-letter effect across morpheme boundaries for affixed words (both prefixed words and suffixed words). Experiment 3 replicated the previous findings, and also revealed that, for polymorphemic words, transposed-letter priming effects occurred for within-morpheme transpositions. Taken together, these findings support the view that morphological decomposition operates at an early stage of visual word recognition.

Adult↗