A widely used task in the research on spoken word recognition is phoneme monitoring, in which subjects have to detect phonemes in spoken words. It is generally assumed that this task is performed using phonetic or phonological representations of words only. To test whether an orthographic representation of the words is employed as well, an experiment was conducted in which Dutch subjects monitored for phonemes with either a primary or secondary spelling in phonologically matched spoken words and nonwords. Phoneme monitoring times were slower when the phoneme had a secondary spelling than when it had a primary spelling. The effect was greater after than before the uniqueness point of the word, and monitoring times were faster for words than for nonwords. These findings indicate that an orthographic representation of words is engaged in phoneme monitoring.
The origins of several phenomena of number-fact retrieval were investigated by having children in Grades 3 and 4 memorize alphaplication facts (arithmetic-like memory items composed of letters instead of numbers). Alphaplication performance paralleled memory for arithmetic facts in several important respects: Results showed (a) a large performance advantage for tie (e.g., E , E = j) over nontie problems (E , I = p), (b) that most errors involved answers from the correct alpha-table, (c) that response times and error rates were strongly correlated across problems, (d) that the correct answers to poorly learned problems tended to be the most common error responses, and (e) that performance was lower for problems introduced later in the learning sequence. Taken together, these findings support a network-interference approach (Campbell & Graham, 1985) to memory for arithmetic facts.
The spontaneous or induced use of an organization strategy is examined on free recall tasks with 10-year-old children classified as rather global or rather analytical at the Group embedded Figures test. The experimental procedure include three successive and identical tests followed by two differed tasks, one requiring a transfer of maintenance and the other a transfer of generalization. The experimental group, who attended a simple illustration of the organization strategy before the second test, applied the strategy quickly and successfully: for these subjects, one does not note differences between global or analytical subjects in the recall performance; however, the global subjects modify their study strategy of the material on the generalization task. For the control group, global or analytical subjects have a different evolution for the performance and the strategic attitude according to the procedure. The analytical subjects are different from global subjects on the generalization task.
This study examines the interaction between the development of cognitive strategies and self-monitoring abilities in children aged 8 to 14. Children were tested individually on eight proportionality problems presented with the balance-scale task. Cognitive development was assessed by the strategy used and the performance on each problem. The indicators of self-monitoring were: latencies before and after the solution of a problem, self-evaluation of one's ability to make the balance scale stay level, proportion of oriented moves on die balance scale, and persistence on a problem. Children's self-monitoring reactions to failure were assessed by changes in strategies, verbal explanations, self-evaluation of performance, and latencies. Results showed an interaction between the complexity of the items and cognitive level. On more complex items, children of lower cognitive levels had shorter latencies, made more (but less oriented) moves on the balance scale, persisted less in their activity, and had more difficulty to evaluate properly their performance. Following failure, children of lower cognitive levels did a less accurate evaluation of their performance, modified their strategy, and did not change their verbal justification, whereas children of higher cognitive levels did a good evaluation of their performance, did not change their strategy, and had the tendency to change their verbal justification. Following failure, all children took less time planning their activity. The results suggest that self-monitoring abilities develop according to the development of cognitive strategies and are mediated by the complexity of the task.
To examine the neurotoxic effects of domoic acid, an amnesic shellfish toxin, electroencephalographic and behavioural experiments were conducted on 38 rats. Injection of domoic acid (0.5-1.0 mg/kg intravenously, or 0.04-0.08 microgram intraventricularly) caused seizure discharges in the hippocampus, tonic-clonic convulsions, and death within a few days. Convulsions and ensuing death were prevented by diazepam. Animals pretreated with diazepam (5 mg/kg, ip) tolerated intraventricular dose of domoic acid 0.4 microgram, but showed a loss of pyramidal neurons mainly in the CA3, CA4, and a part of CA1 areas of the dorsal hippocampus. Learning of a radial maze task was severely impaired in naive rats after intraventricular injection of domoic acid (and diazepam, ip). In the animals previously trained on the maze task, domoic acid interfered with relearning of the same task. These effects appear similar to those of kainic acid and are analogous to the symptoms observed in humans who ingested mussels tainted with domoic acid.
Under the assumption of a general viewpoint, particular image properties, such as cotermination, straightness, and parallelism, can be used to infer, more or less reliably, the corresponding characteristics in the world. In this paper, the literature about these nonaccidental properties (NAPs) is reviewed to trace its historical roots, to list the properties that function as NAPs, and to discuss the psychological evidence for their detection and use. Against this background, four experiments are reviewed and four are fully described that were designed to test the perceptual use of skewed symmetry (SS), which results from orthographic projection of planar bilateral or mirror symmetry (BS). Despite the large symmetry advantage obtained in all experiments, SS is only perceived as BS-in-depth in cases of closed polygons or dot patterns with higher-order types of symmetry. In all random dot patterns and in some symmetric patterns with low "Gestalt", subjects relied on more local groupings which are qualitatively affine invariant, such as clusters based on proximity or curvilinearity. Based on previous approaches in the literature and these new findings, I suggest some distinctions between different ways of using NAPs, which might foster further research.
The modern "textbook" view of visual perception contains an inherent paradox. On the one hand, it claims that relatively simple edge-extraction processes requires a stimulus exposure of approximately 50 ms. On the other hand, it says that the identification of objects in photographs and line-drawings can be highly accurate with exposure durations as short as 100 ms. It is tempting to conclude that all the difficult work of perception occurs in the 50 ms that elapse between when these two tasks are accomplished. This article argues against this view, suggesting instead that much more than edge-extraction is accomplished by the early visual processes. To illustrate this view, a computational model is described that is capable of recovering the 3-D orientation of objects from some line-drawings, rapidly and in parallel. Data from recent visual search experiments with human observers are presented in support of this model and the implications of this view for the "textbook" view are discussed.
Relationships between clinical retardation (measured by the Hamilton Depression Inventory) and selective attention (measured with a computerized version of the Stroop word colour test) were studied in a population Of 2I depressed patients. Stroop interference was higher in depressed patients than in normals. Desynchronized presentations of the distractor and the target and intervals between responses and succeeding stimuli permitted depressed subjects to respectively apply and lift inhibition of the distractor so that their interference was reduced to control levels. Finally, successive inhibition scores were correlated with the retardation score in depressed subjects. The results are consistent with the hypothesis of a retardation in the application and the lifting of cognitive inhibition in depression.
A connectionist model of visual search is presented, in which search is determined by patterns of grouping between distractors and between the target and the distractors. Grouping is based on conjunctive relations between simple form elements (corners, line-end terminators), and uses principles of similarity and spatial proximity. In its normal, 'unlesioned' state, the model simulates the search data generated by human subjects when they search for simple form conjunctions amongst either homogeneous or heterogeneous distractors (Humphreys & Muller, in press). In this paper, the performance of the model is examined after the model is subject to various types of 'lesion'. 'Lesioning' is produced either by increasing the internal noise on the activation functions governing the interactions between processing units, or by eliminating processing units from different loci in the model. Increasing the internal noise within the model, or lesioning units within 'high-level' processing stages, can generate the selective effects on search found in a detailed single case study of an agnosic patient (Humphreys, Riddoch, Quinlan, Price & Donnelly, this volume): Namely, there is selective disruption of search for a form conjunction amongst homogeneous distractors relative to search for the same target amongst heterogeneous distractors. This selective effect can be attributed to the 'lesion' disrupting grouping between distractors, which normally facilitates search with homogeneous distractors. The simulations demonstrate that (1) search processes can be disrupted by adding internal noise to search functions, (2) that there can be selective effects on grouping processes, and (3) that these selective effects can be associated with different types of lesion to different stages in the model. The implications of the simulations for understanding visual processing impairments in agnosia are discussed.
Abstract An inhibition-based fan effect hypothesis was tested using a negative priming paradigm in Experiments I and 2 and a short-term memory scanning paradigm in Experiment 3. In Experiment I and 2, the time to name a letter (surrounded by I to 3 distractor letters) was longer when it had been a distractor on the previous display than in a control condition where the target letter had not been one of the distractors in the previous display. This negative priming effect attenuated as the number of distractors in the previous display increased. We interpret this fan effect as a manifestation of a limited capacity spreading inhibition counterpart to spreading activation. Median split data, isolating faster from slower subjects, suggested that an irrelevancy heuristic may be involved because the best performances (fastest overall RTs) were produced by people who also produced relatively greater magnitudes of negative priming. By having irrelevant information momentarily less available, overall advantages in processing appear to be gained through reduced interference from distracting stimuli. The juxtaposition of an irrelevancy with a relevancy heuristic (Anderson, 1983a) supports the possible existence of a spreading inhibition counterpart of spreading activation. Several key predictions based upon this framework were confirmed in a modified short-term memory scanning task in Experiment 3.
In order to recognize an object, the visual system must make abstraction of proximal stimulus variations concomitant with the incidental vantage point. Theoretical models can be distinguished according to the degree to which they require the achievement of viewpoint independence prior to matching a stored object model. Recognition-by-components is one theory which incorporates the realization of general viewpoint invariance as one of its hallmarks. Some aspects of this theory, especially the orientation independence of the represented relations between object parts, are scrutinized. Next, an alternative approach is sketched in which object recognition is accomplished on the basis of a stimulus description which is dependent on the object's orientation, but which makes abstraction of other stimulus variations. Relevant neurophysiological findings are discussed, as well as behavioural evidence from experiments investigating orientation-dependent priming effects in the perception of biological motion.
When we view a natural visual scene, we seem able to determine effortlessly the scene's semantic category, constituent objects, and spatial relations. How do we accomplish this visual-cognitive feat? The commonly held explanation is known as the schema hypothesis, according to which a visual scene is rapidly identified as a member of a semantic category, and predictions generated from the scene category are then used to aid subsequent object identification. In this paper I will first outline and offer a critique of the evidence that has been taken to support the schema hypothesis. I will then offer an alternative framework for understanding scene processing, which I will call the local-processing hypothesis. This hypothesis assumes a modular, informationally-encapsulated architecture, and explicitly includes the role of covert visual attention in scene processing.
In this study the recall of autobiographical and public events across the lifespan was examined in a sample of middle-aged and older-aged adults. The tasks were modified versions of one first introduced by Galton (1879), and they required subjects to recall events from specific time periods across their entire lifespan. The four tasks differed in the nature of the episodes requested (autobiographical or public) and whether recall was word-cued or non-word-cued. Verification of public events was assessed archivally, and autobiographical events were verified by a sample of relatives for a subgroup of the subjects and reported events. The results indicated that memory for public events decreases with increased age of the subject, but this effect is not generally found for the recall of autobiographical events. The older-aged subjects were able to recall an equal number of autobiographical episodes from all life segments, whereas recall of news events tended to decrease with remoteness of the episode. These data are contrary to those models that posit general memory loss as a function of age or of remoteness of the events.
A series of visual search experiments are reported examining pattern processing in a visual agnosic patient. We examined search for targets defined by: (I) the combination of their features relative to homogeneous distractors; (2) the combination of their features relative to heterogeneous distractors; and (3) a single feature difference relative to the distractors (their orientation). Normal subjects demonstrate evidence of spatially parallel search when combined-feature targets are detected against homogeneous distractors, and when targets are defined by a salient feature difference. There are non-linear effects of the number of distractors present, and absent responses can be as fast as present. In contrast, search times for combined-feature targets amongst heterogeneous distractors increase linearly with display size, with the slope for absent responses about twice that for present. The contrast between search for combined-feature targets amongst homogeneous and heterogeneous distractors can be attributed to the effects of grouping between distractors and between distractors and targets (Duncan & Humphreys, 1989, 1992; Humphreys & Muller, in press). Grouping between homogeneous distractors facilitates search. An agnosic patient, HJA, showed normal search functions for single-feature targets and for combined-feature targets amongst heterogeneous distractors. However, he was impaired at search for combined-feature targets amongst homogeneous distractors. This suggests that HJA is selectively impaired at grouping conjunctions of form features. The relations between HJA's agnosia and his problem in the parallel grouping of form conjunctions are discussed, as are the implications of the work for understanding normal vision.
Objects likely to appear in a given real-world scene are frequently found to be easier to recognize. Two different sources of contextual information have been proposed as the basis for this effect: global scene background and individual companion objects. The present paper examines the relative importance of these two elements in explaining the context-sensitivity of object identification in full scenes. Specific sequences of object fixations were elicited during free scene exploration, while fixation times on designated target objects were recorded as a measure of ease of target identification. Episodic consistency between the target, the global scene background, and the object fixated just prior to the target (the prime), were manipulated orthogonally. Target fixation times were examined for effects of prime and background. Analyses show effects of both factors, which are modulated by the chronology and spatial extent of scene exploration. The results are discussed in terms of their implications for a model of visual object recognition in the context of real-world scenes.
Visual science is currently a highly active domain, with much progress being made in fields such as colour vision, stereo vision, perception of brightness and contrast, visual illusions, etc. But the ''real'' mystery of visual perception remains comparatively unfathomed, or at least relegated to philosophical status: Why it is that we can see so well with what is apparently such a badly constructed visual apparatus?In this paper I will discuss several defects of vision and the classical theories of how they are overcome. I will criticize these theories and suggest an alternative approach, in which the outside world is considered as a kind of external memory store which can be accessed instantaneously by casting one's eyes (or one's attention) to some location. The feeling of the presence and extreme richness of the visual world is, under this view, a kind of illusion, created by the immediate availability of the information in this external store.
The purpose of the experiments reported was to examine how novel, three-dimensional shapes are represented in long-term memory and how this might be differentially affected by monocular and binocular viewing. Three experiments were conducted. The first experiment established that slide projections of the novel objects could be recognized readily if seen in the same orientation as seen during learning. The second and third experiments examined generalization to novel depth rotations of the objects. The second experiment used slide projections of the objects. The results indicated that the representation of the objects seen during training was quite viewpoint-specific as recognition of objects in novel orientations was relatively poor. In the third experiment subjects were shown the real objects under monocular or binocular viewing. Overall, the results are consistent with a growing body of recent research showing that, at least under certain conditions, the visual system stores viewpoint-specific representations of objects.
