Letter processing in upright bigrams predicts reading fluency variations in children

Fluent reading is an important milestone in education, but we lack a clear understanding of why children vary so widely in attaining it. Language-related factors such as rapid automatized naming (RAN) and phonological awareness have been identified as important factors that explain reading fluency. However, whether any aspects of visual orthographic processing also explain reading fluency beyond phonology is unclear. To investigate these issues, we tested primary school children (n = 68) on four tasks: two reading fluency tasks (word reading and passage reading), a RAN task to measure naming speed, and a visual search task using letters and bigrams. Bigram processing in visual search was accurately explained by single-letter discrimination, and error patterns were unrelated to fluency or bigram frequency, ruling out the contribution of specialized bigram detectors. As expected, the RAN score was strongly correlated with reading fluency. Importantly, there was a highly specific association between reading fluency and upright bigram processing in visual search. This association was specific to upright but not inverted bigrams and to bigrams with normal but not large letter spacing. It was explained by increased letter discrimination across bigrams and reduced interactions between letters within bigrams. Thus, fluent reading is accompanied by specialized changes in letter processing within bigrams

Investigation on Perception and Behavior of the American Black Bear (\u3cem\u3eUrsus americanus\u3c/em\u3e)

Behavioral information concerning the American black bear Ursus americanus is limited. The present study was conducted to assess various aspects of ingestive behavior and visual discrimination of the black bear using two captive females. Information available pertaining to the management of black bears in captivity is also limited. Therefore a large portion of the study revolved around the care and maintenance of the bears in a semi-natural enclosure. The ingestive behaviors were studied using ethological observations and a longitudinal food preference test. Observations were obtained as the subjects procured and consumed food items both naturally occurring and introduced into the enclosure. The observed feeding behaviors were discussed in three categories: foraging, predation, and consumption. The foraging behaviors appeared to be uncomplicated and consisted primarily of apparently random walking and use of the front paws to dig and manipulate objects in the enclosure. Olfactory scanning was integrated with locomotion and use of the paws. Predatory behaviors were infrequently observed but are described. Detailed descriptions of the consumption of the native food items (acorns, blackberries, and grass) were based on motion picture analysis. Visual orientation toward the food items was particularly evident and is considered an important facit of the ingestive behaviors. The bears were also found to be very clean feeders, consuming very little debris. The preferences for two sets of food items (native food items and non-native food items) was determined during a one year testing program. The bears were found to exhibit definite scalable preferences among both sets of foods. The preferences were significantly correlated between the subjects and were consistent throughout the one year period. The consistency of preference among seasons indicated that the naturally occurring diet of the black bear is controlled by availability of the foods. In the native food test acorns were the most preferred. In the non-native food test fish was the most preferred food. The foods most highly preferred were rich either in protein or carbohydrates. The carbohydrate preference, unusual for a member of the order Carnivora, is considered a function of the change to herbivorous dietary patterns in the bear. The research on visual capacities of the captive bears consisted of two discrimination studies. The bears were tested for their abilities to perform discriminations on the basis of hue and pattern using specially designed methods involving small painted containers. The basic task was a two-choice correction procedure with food reinforcement. The results of the color vision testing indicate that blue was successfully discriminated from gray, green, red, and yellow. Green was successfully discriminated from gray, blue and red. The acquisition of the discriminations was very rapid. The consistency of the hue discrimination and the rapidity of learning indicated that the subjects were very adept at hue discrimination and, most likely, utilized this ability with frequency. The form discrimination study was designed to assess one bear\u27s abilities to differentiate and recognize patterns. It was found that the ability to choose the correct stimulus was not affected by size of the stimuli, configurational placement, or the introduction of novel negative stimuli. The reversal of backgrounds produced an initial but very short period of confusion. The retention of the discrimination was found to be perfect after four and eight month delays. The rate of learning the initial discrimination was also very rapid. It was concluded that the bear was very capable of making visual discriminations on the basis of pattern

Attention mechanisms in the CHREST cognitive architecture

In this paper, we describe the attention mechanisms in CHREST, a computational architecture of human visual expertise. CHREST organises information acquired by direct experience from the world in the form of chunks. These chunks are searched for, and verified, by a unique set of heuristics, comprising the attention mechanism. We explain how the attention mechanism combines bottom-up and top-down heuristics from internal and external sources of information. We describe some experimental evidence demonstrating the correspondence of CHREST’s perceptual mechanisms with those of human subjects. Finally, we discuss how visual attention can play an important role in actions carried out by human experts in domains such as chess

Expertise and intuition: A tale of three theories

Several authors have hailed intuition as one of the defining features of expertise. In particular, while disagreeing on almost anything that touches on human cognition and artificial intelligence, Hubert Dreyfus and Herbert Simon agreed on this point. However, the highly influential theories of intuition they proposed differed in major ways, especially with respect to the role given to search and as to whether intuition is holistic or analytic. Both theories suffer from empirical weaknesses. In this paper, we show how, with some additions, a recent theory of expert memory (the template theory) offers a coherent and wide-ranging explanation of intuition in expert behaviour. It is shown that the theory accounts for the key features of intuition: it explains the rapid onset of intuition and its perceptual nature, provides mechanisms for learning, incorporates processes showing how perception is linked to action and emotion, and how experts capture the entirety of a situation. In doing so, the new theory addresses the issues problematic for Dreyfus’s and Simon’s theories. Implications for research and practice are discussed

Nonstimulated early visual areas carry information about surrounding context

Even within the early sensory areas, the majority of the input to any given cortical neuron comes from other cortical neurons. To extend our knowledge of the contextual information that is transmitted by such lateral and feedback connections, we investigated how visually nonstimulated regions in primary visual cortex (V1) and visual area V2 are influenced by the surrounding context. We used functional magnetic resonance imaging (fMRI) and pattern-classification methods to show that the cortical representation of a nonstimulated quarter-field carries information that can discriminate the surrounding visual context. We show further that the activity patterns in these regions are significantly related to those observed with feed-forward stimulation and that these effects are driven primarily by V1. These results thus demonstrate that visual context strongly influences early visual areas even in the absence of differential feed-forward thalamic stimulation

Location-Specific Cortical Activation Changes during Sleep after Training for Perceptual Learning

Visual perceptual learning is defined as performance enhancement on a sensory task and is distinguished from other types of learning and memory in that it is highly specific for location of the trained stimulus. The location specificity has been shown to be paralleled by enhancement in functional magnetic resonance imaging (fMRI) signal in the trained region of V1 after visual training. Although recently the role of sleep in strengthening visual perceptual learning has attracted much attention, its underlying neural mechanism has yet to be clarified. Here, for the first time, fMRI measurement of human V1 activation was conducted concurrently with a polysomnogram during sleep with and without preceding training for visual perceptual learning. As a result of predetermined region-of-interest analysis of V1, activation enhancement during non-rapid-eye-movement sleep after training was observed specifically in the trained region of V1. Furthermore, improvement of task performance measured subsequently to the post-training sleep session was significantly correlated with the amount of the trained-region-specific fMRI activation in V1 during sleep. These results suggest that as far as V1 is concerned, only the trained region is involved in improving task performance after sleep

Differing instructional needs for children of similar reading achievement grades two, four, and six

Thesis (Ed.M.)--Boston Universit

Visual search and decision making in bees: time, speed and accuracy

An insect searching a meadow for flowers may detect several flowers from different species per second, so the task of choosing the right flowers rapidly is not trivial. Here we apply concepts from the field of visual search in human experimental psychology to the task a bee faces in searching a meadow for familiar flowers, and avoiding ‘‘distraction’’ by unknown or unrewarding flowers. Our approach highlights the importance of visual information processing for understanding the behavioral ecology of foraging. Intensity of illuminating light, target contrast with background (both chromatic and achromatic), and number of distractors are all shown to have a direct influence on decision times in behavioral choice experiments. To a considerable extent, the observed search behavior can be explained by the temporal and spatial properties of neuronal circuits underlying visual object detection. Our results also emphasize the importance of the time dimension in decision making. During visual search in humans, improved accuracy in solving discrimination tasks comes at a cost in response time, but the vast majority of studies on decision making in animals have focused on choice accuracy, not speed. We show that in behavioral choice experiments in bees, there is a tight link between the two. We demonstrate both between-individual and within- individual speed-accuracy tradeoffs, whereby bees exhibit considerable behavioral flexibility in solving visual search tasks. Motivation is an important factor in selection of behavioral strategies for a search task, and sensory discrimination capabilities may be underestimated by studies that quantify accuracy of behavioral choice but neglect the temporal dimension

Five seconds or sixty? Presentation time in expert memory

The template theory presented in Gobet and Simon (1996a, 1998) is based on the EPAM theory (Feigenbaum & Simon, 1984; Richman et al., 1995), including the numerical parameters that have been estimated in tests of the latter; and it therefore offers precise predictions for the timing of cognitive processes during the presentation and recall of chess positions. This paper describes the behavior of CHREST, a computer implementation of the template theory, in a task when the presentation time is systematically varied from one second to sixty seconds, on the recall of both game and random positions, and compares the model to human data. As predicted by the model, strong players are better than weak players with both types of positions. Their superiority with random positions is especially clear with long presentation times, but is also present after brief presentation times, although smaller in absolute value. CHREST accounts for the data, both qualitatively and quantitatively. Strong players’ superiority with random positions is explained by the large number of chunks they hold in LTM. Strong players’ high recall percentage with short presentation times is explained by the presence of templates, a special class of chunks. The model is compared to other theories of chess skill, which either cannot account for the superiority of Masters with random positions (models based on high-level descriptions and on levels of processing) or predict too strong a performance of Masters with random positions (long-term working memory)

Change blindness: eradication of gestalt strategies

Arrays of eight, texture-defined rectangles were used as stimuli in a one-shot change blindness (CB) task where there was a 50% chance that one rectangle would change orientation between two successive presentations separated by an interval. CB was eliminated by cueing the target rectangle in the first stimulus, reduced by cueing in the interval and unaffected by cueing in the second presentation. This supports the idea that a representation was formed that persisted through the interval before being 'overwritten' by the second presentation (Landman et al, 2003 Vision Research 43149–164]. Another possibility is that participants used some kind of grouping or Gestalt strategy. To test this we changed the spatial position of the rectangles in the second presentation by shifting them along imaginary spokes (by ±1 degree) emanating from the central fixation point. There was no significant difference seen in performance between this and the standard task [F(1,4)=2.565, p=0.185]. This may suggest two things: (i) Gestalt grouping is not used as a strategy in these tasks, and (ii) it gives further weight to the argument that objects may be stored and retrieved from a pre-attentional store during this task