Biomedical subjects

Andrew W Ellis

Publications and source records attributed to Andrew W Ellis.

18 recordsLinked to original sources

PubMed2006

Word finding in the damaged brain: probing Marshall's caveat.

Marshall (1977) constructed a plausible simulation of "anomic" speech out of the 100 most common words in the English language. He suggested that impaired access to lower frequency vocabulary might underlie anomic word finding difficulties. But he also noted that another factor, age of acquisition, may exert an influence, with anomic patients experiencing particular difficulty with later acquired vocabulary. A review of research on word-finding in aphasia and other neuropsychological conditions suggests that Marshall (1977) may have been right on both counts, and that in many patients both frequency of use and age of acquisition influence the likelihood that a given word will be able to be accessed and used. Theoretical accounts of why the age of acquisition of words might affect their retention or loss following brain injury in adulthood are considered.

Age Factors↗

PubMed2006

Unilateral neglect is not unilateral: evidence for additional neglect of extreme right space.

Six patients with visuospatial neglect following right hemisphere lesions were given three tasks that assessed performance in areas of space ranging from extreme left to extreme right. A line bisection task required the patients to detect and bisect lines of four different lengths at seven left-right spatial locations, a number report task required the patients to name 11 two-digit numbers in a left-right array, and a tiling task required patients to place small black tiles over the black squares of a grid that stretched from 65 degrees left to 65 degrees right. Performance was compared with that of 20 age-matched controls. The patients showed the characteristic signs of left-side neglect in left space, extending to the central midline. Performance was relatively normal in centre-right space but all 6 patients showed signs of neglect of extreme right space (60 degrees to the right of the midline and beyond). We propose that neglect is best characterised as a bilateral, asymmetrical compression of experienced space in which the constriction extends further from the left than from the right but nevertheless affects both sides of space.

Aged↗

PubMed2006

Age of acquisition affects object recognition and naming in patients with Alzheimer's disease.

Twenty-two patients with a diagnosis of dementia of the Alzheimer type (DAT) and a comparison group of 22 age-matched individuals took part in an object decision and picture naming task. The age of acquisition (AoA) of the picture names was manipulated (25 early, 25 late). The comparison group identified significantly more objects as real than the patients. While the comparison group made very few errors in object decision, DAT patients failed to classify significantly more late than early acquired objects as real. The patients also named significantly fewer pictures than the comparison group, showing a differential impairment in naming late acquired objects. Late acquired objects induced proportionately more visual errors in the patients than did early acquired objects. The results are discussed in terms of current theories of age of acquisition and of the impact of Alzheimer's disease on lexical and semantic processing.

Aged↗

PubMed2006

Orthographic complexity and word naming in Italian: some words are more transparent than others.

Italian is a language with a transparent orthography in which printed words can be translated into the correct sequence of phonemes using a limited set of rules. The rules of letter-sound conversion are, however, simpler for some letters than for others: The pronunciations of sequences involving the letters c and g are determined by complex (i.e., context-sensitive) rules that depend on the letters that follow them. In this article, we report two experiments in which Italian participants read aloud words containing simple or complex letter-sound conversion rules. In Experiment 1, we found that words containing complex rules were read more slowly than words containing simple, noncontextual rules. In Experiment 2, we found that the effect of rule complexity on naming speed held for low-frequency words but not high-frequency words. The results are interpreted in terms of a dual-route model in which rule complexity effects arise from sublexical procedures that are more involved in reading low-frequency words than high-frequency words. The experimental material used in this study may be downloaded from www.psychonomic.org/archive.

Humans↗

PubMed2005

The age of acquisition of words produced in a semantic fluency task can reliably differentiate normal from pathological age related cognitive decline.

This study examined differences in the characteristics of words produced by healthy elderly controls and by patients with Alzheimer's disease (AD) in a semantic fluency task (generating words from the categories of animals and fruit). Ninety-six AD patients (MMSE 13-29) and 40 controls matched for age and socio-cultural background completed a semantic fluency task. Length, frequency, typicality and age of acquisition (AoA) values were obtained for each word generated. In comparison with controls, AD patients generated fewer items, and their items were higher in frequency, shorter in length, more typical and earlier in AoA. Discriminant function analysis showed that AoA was the best predictor of group membership (patient/control). The mean AoA of words generated correctly classified 95% of controls and 88% of patients.

Age of Onset↗

PubMed2005

Category norms for 500 Spanish words in five semantic categories.

This study presents a database of 500 words from five semantic categories: animals, body parts, furniture, clothing, and intelligence. Each category contains 100 words, and data on lexical availability, age of acquisition, imageability, typicality, concept familiarity, written word frequency, and word length in number of syllables are provided with each word. The full set of norms may be downloaded from www.psychonomic.org/archive.

Adolescent↗

PubMed2004

Evaluating a split processing model of visual word recognition: effects of orthographic neighborhood size.

The split fovea theory proposes that visual word recognition of centrally presented words is mediated by the splitting of the foveal image, with letters to the left of fixation being projected to the right hemisphere (RH) and letters to the right of fixation being projected to the left hemisphere (LH). Two lexical decision experiments aimed to elucidate word recognition processes under the split fovea theory are described. The first experiment showed that when words were presented centrally, such that the initial letters were in the left visual field (LVF/RH), there were effects of orthographic neighborhood, i.e., there were faster responses to words with high rather than low orthographic neighborhoods for the initial letters ('lead neighbors'). This effect was limited to lead-neighbors but not end-neighbors (orthographic neighbors sharing the same final letters). When the same words were fully presented in the LVF/RH or right visual field (RVF/LH, Experiment 2), there was no effect of orthographic neighborhood size. We argue that the lack of an effect in Experiment 2 was due to exposure to all of the letters of the words, the words being matched for overall orthographic neighborhood count and the sub-parts no longer having a unique effect. We concluded that the orthographic activation found in Experiment 1 occurred because the initial letters of centrally presented words were projected to the RH. The results support the split fovea theory, where the RH has primacy in representing lead neighbors of a written word.

Adolescent↗

PubMed2004

Length, formats, neighbours, hemispheres, and the processing of words presented laterally or at fixation.

It has long been known that the number of letters in a word has more of an effect on recognition speed and accuracy in the left visual field (LVF) than in the right visual field (RVF) provided that the word is presented in a standard, horizontal format. After considering the basis of the length by visual field interaction two further differences between the visual fields/hemispheres are discussed: (a) the greater impact of format distortion (including case alternation) in the RVF than in the LVF and (b) the greater facilitation of lexical decision by orthographic neighbourhood size (N) in the LVF than in the RVF. In the context of split fovea accounts of word recognition, evidence is summarised which indicates that the processing of words presented at fixation is affected by the number of letters to the left of fixation but not by the number of letters to the right and by the number of orthographic neighbours activated by letters to the left of fixation but not by the number of orthographic neighbours activated by letters to the right of fixation. A model of word recognition is presented which incorporates the notion that the left hemisphere has sole access to a mode of word recognition that involves parallel access from letter forms to the visual input lexicon, is disrupted by format distortion, and does not employ top-down support of the letter level by the word level.

Brain↗

PubMed2003

Interhemispheric integration of letter stimuli presented foveally or extra-foveally.

Two experiments are reported in which participants decided whether a single target letter presented below and to the left or right of fixation matched either of two probe letters presented above the fixation cross to the left and right. The level of matching required was either physical (A-A) or abstract (A-a). All three letters were presented either extra-foveally (Experiment 1) or within the fovea (Experiment 2). In both experiments, physical matching was faster than abstract matching. Physical matching was faster within than across visual fields while abstract matching showed the opposite pattern. Matching was faster when the matching probe letter was in the LVF than when it was in the RVF. Importantly, the pattern of results was the same for extra-foveal and foveal presentations, supporting the theory that the representation of the fovea is split down the middle into two visual fields rather then being bilateral. The practical implication following this study is that lateralization studies can be performed with closer to fixation stimuli presentation.

Adult↗

PubMed2003

Lexical processing in Spanish patients with probable Alzheimer's disease.

Twenty Spanish patients with probable Alzheimer's disease (AD) and 20 matched controls were given a battery of 17 tasks involving object recognition and the spoken and written perception and production of words and non-words. The AD patients were significantly impaired on nine of the tasks. Prominent among these were tasks that involve semantic processing, though non-word reading was also impaired. Performance on a category fluency task best discriminated AD patients from controls. It is proposed that impairment to semantic processing underlies most of the observed deficits on lexical processing tasks in patients with early AD, but that non-word reading may be sensitive to additional, mild impairments to phonological representations caused by extension of the degenerative process from anterior to posterior temporal regions.

Aged↗

PubMed2003

Orthographic and phonological priming in the two cerebral hemispheres.

The patterns of activation invoked in the two cerebral hemispheres by written words may be different. Two lexical decision experiments investigated several aspects of such activation patterns. Experiment 1 tested phonological and orthographic priming in the hemispheres, manipulating two levels of phonological and two levels of orthographic similarity. Orthographic priming in the left visual field (LVF) was significantly larger than in the right visual field (RVF). In Experiment 2, primes were phonologically identical to the targets (homophones) but differed in their orthographic similarity. For LVF targets, only orthographic priming was significant, whereas for RVF targets, the phonological primes were effective regardless of their orthographic similarity. The results imply that orthographic activation, though maintained by both hemispheres, is more characteristic of right hemisphere word recognition processes, whereas phonological priming is more characteristic of left hemisphere processes.

Journal Article↗

PubMed2002

Orthographic neighborhood effects in the right but not in the left cerebral hemisphere.

Two lexical decision experiments investigated orthographic neighborhood effects in the hemispheres. In the first experiment, lexical decision was affected by orthographic neighborhood size when stimuli were presented to the right hemisphere (RH) but not to the left hemisphere (LH). In a four-field masked-prime lexical decision task (Experiment 2), a larger shared orthographic neighborhood between prime and target facilitated lexical decision in the RH but not in the LH. The patterns of activation invoked in the two cerebral hemispheres by a written word and its orthographic neighbors may be qualitatively different.

Adolescent↗

PubMed2002

Word length and orthographic neighborhood size effects in the left and right cerebral hemispheres.

Previous studies have reported an interaction between visual field (VF) and word length such that word recognition is affected more by length in the left VF (LVF) than in the right VF (RVF). A reanalysis showed that the previously reported effects of length were confounded with orthographic neighborhood size (N). In three experiments we manipulated length and N in lateralized lexical decision tasks. Results showed that length and VF interacted even with N controlled (Experiment 1); that N affected responses to words in the LVF but not the RVF (Experiment 2); and that when length and N were combined, length only affected performance in the LVF for words with few neighbors.

Adolescent↗

PubMed2002

Long-term effects of covert face recognition.

Covert face recognition has previously been thought to produce only very short-lasting effects. In this study we demonstrate that manipulating subjects' attentional load affects explicit, but not implicit memory for faces, and that implicit effects can persist over much longer intervals than is normally reported. Subjects performed letter-string tasks of high vs. low perceptual load (Lavie, N. (1995). Perceptual load as a necessary condition for selective attention. Journal of Experimental Psychology: Human Perception and Perfomance. 21, 451-468.), while ignoring task-irrelevant celebrity faces. Memory for the faces was then assessed using (a) a surprise recognition test for the celebrities' names, and (b) repetition priming in a face familiarity task. The load manipulation strongly influenced explicit recognition memory, but had no effect on repetition priming from the same items. Moreover, faces from the high load condition produced the same amount of priming whether they were explicitly remembered or not. This result resolves a long-standing anomaly in the face recognition literature, and is discussed in relation to covert processing in prosopagnosia.

Attention↗

PubMed2002

Aphasic naming in Spanish: predictors and errors.

Sixteen Spanish aphasic patients named drawings of objects on three occasions. Multiple regression analyses were carried out on the naming accuracy scores. For the patient group as a whole, naming was affected by visual complexity, object familiarity, age of acquisition, and word frequency. The combination of variables predicted naming accuracy in 15 of the 16 individual patients. Age of acquisition, word frequency, and object familiarity predicted performance in the greatest number of patients, while visual complexity, imageability, animacy, and length all affected performance in at least two patients. High proportions of semantic and phonological errors to particular objects were associated with objects having early learned names while high proportions of no-response errors were associated with low familiarity and low visual complexity. It is suggested that visual complexity and object familiarity affect the ease of object recognition while word frequency affects name retrieval. Age of acquisition may affect both stages, accounting for its influence in patients with a range of different patterns of disorder.

Adult↗

PubMed2002

Case alternation and length effects in lateralized word recognition: studies of English and Hebrew.

Effects of CaSe AlTeRnAtIoN were studied in two lateralized visual lexical decision experiments. We manipulated word length and letter case (UPPER, lower and MiXeD) in both English (Exp. 1, N=60) and Hebrew (Exp. 2, N=60). The previously reported visual field and word length interaction was found for upper and lower case presentation, but not for MiXeD CaSe, where both fields were affected by word length. The effects of case alternation are discussed in light of a new lateralized word recognition theory.

Adolescent↗

PubMed2002

What exactly interacts with spelling-sound consistency in word naming?

Word frequency, age of acquisition (AoA), and imageability were combined with spelling-sound consistency, and their effects on word naming were examined. Frequency and AoA interacted with consistency (Experiments 1 and 2). Imageability did not (Experiment 3). Experiment 4 replicated Experiment 2 of E. Strain, K. E. Patterson, and M. S. Seidenberg's (1995) study and obtained the same apparent effect of imageability on naming. That effect disappeared when AoA was entered as a covariate. An explanation of the interactions of consistency with frequency and AoA is offered in terms of the properties of adaptive connectionist networks given gradual and cumulative training.

Humans↗

PubMed2002

Searching for threat.

In a series of experiments, a visual search task was used to test the idea that biologically relevant threatening stimuli might be recognized very quickly or capture visuo-spatial attention. In Experiment 1, there was evidence for both faster detection and faster search rates for threatening animals than for plants. However, examination of the basis of this effect in Experiment 2 showed that it was not due to threat per se, as detection and search rate advantages were found for pleasant rather than threatening animals compared to plants. In Experiment 3, participants searched for the plants and pleasant and threatening animals used in Experiments 1 and 2, among a fixed heterogeneous selection of non-target items. There was no search rate or detection advantage for threatening animals compared to pleasant animals or plants. The same targets and non-targets as those used in Experiment 3 were also used in Experiment 4. In Experiment 4, participants searched for targets that were presented either close to or distant from an initial fixation point. There was no evidence for a "threat" detection advantage either close to or distant from the cross. Finally, an experiment was conducted in which target categories (fruit, flowers, and animals) were not pre-specified prior to each trial block. There were no differences in reaction times to detect pleasant animals, threatening animals, or fruit. We conclude that the visual search paradigm does not readily reveal any biases that might exist for threatening stimuli in the general population.

Female↗