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PubMed1994

Increases of excitatory receptive fields of retinal ganglion cells in common toads under apomorphine are not associated with size preference in prey-snapping.

After systemic administration of the dopamine agonist apomorphine (APO) in common toads Bufo bufo spinosus, the excitatory receptive fields of retinal R2 and R3 ganglion cells doubled their size and the response activities of these neurons to moving visual stimuli were generally increased. Comparable investigations of the stimulus-response relationships in the snapping behavior of toads pre- and post-APO showed a general increase in the snapping responses, but no shift in the preferred prey size. This is consistent with the current concept, suggesting that size evaluation in amphibians does not rely on retinal ganglion cell output but on interacting networks beyond the retina.

Animals↗
PubMed1993

Triazolam and ethanol effects on human matching-to-sample performance vary as a function of pattern size and discriminability.

The effects of placebo, triazolam (2.0, 4.0 and 8.0 micrograms/kg) and ethanol (0.25, 0.5, 1.0 g/kg) on perceptual-motor performance were examined using a visual pattern matching-to-sample procedure in which pattern size and comparison stimulus discriminability were systematically varied. Baseline response rates and accuracy increased as the discriminability of the comparison stimuli increased. At the highest dose, both drugs decreased response accuracy. This disruption of accuracy was attenuated by increasing the discriminability of non-matching stimuli. Triazolam produced dose-related decreases in response rate while ethanol produced only slight decreases at the highest baseline rates of responding. Thus, triazolam produced response rate slowing at relatively lower doses than ethanol.

Adult↗
PubMed2006

Effect of short and long exposure duration and dual-tasking on a global-local task.

Past research has demonstrated a global advantage in responses to visually presented hierarchical stimuli such that, on incongruent trials, the global form interferes with responses to the local level [Kimchi, R. (1992). Primacy of wholistic processing and global/local paradigm: A critical review. Psychological Bulletin, 112, 24-38]. In Experiment 1, 32 adults performed alternating blocks of global or local identification of hierarchical letter stimuli in which the global and local letters were congruent, incongruent, or neutral, and were presented at either a short (17 ms) or long (100 ms) exposure duration. A global advantage was demonstrated at both durations. In the local-directed task, interference on incongruent, relative to neutral, trials was observed at both exposure durations, but facilitation on congruent trials, relative to neutral trials, was present only when stimuli were presented at the long exposure duration. In Experiment 2, global or local identification was performed by another group of 24 adults at either a long or short exposure duration, and also under conditions of full attention (FA) or dual-task (DT) conditions with a digit-monitoring task. Under FA, we again found significant interference at both exposure durations, but facilitation only at the long exposure duration. Under DT conditions, the pattern of facilitation and interference at the short duration remained unchanged. At the long duration, however, dual-tasking eliminated interference in the RT but not error data, while facilitation was present in both sets of data. Results are in line with a perceptual account of the global advantage, and suggest that facilitation requires consciously-mediated processes, whereas interference does not.

Adolescent↗
PubMed2006

Implicit identification of irrelevant local objects interacts with global/local processing of hierarchical stimuli.

This work aimed at studying interactions between automatic object identification and global/local perceptual processing. We designed a paradigm in which participants were presented with pairs of hierarchically organized items, composed of global forms made up of local forms. Both global and local forms could represent either objects or non-objects. Subjects were instructed to detect whether the two hierarchical items composing a pair were identical or different. In a dissimilar pair, items differed at one level (target level), the other level, made of similar forms on both sides, was irrelevant to perform the task. We hypothesized that the automatic identification of object could affect the global precedence principle defined by Navon. In agreement with our hypothesis, we found that when the irrelevant level was made of objects, the global precedence effect was reversed. In contrast, the irrelevant level had no effect when the target level included only objects, or when the irrelevant level was made of non-object, the global precedence principle was being preserved in these cases. This interaction is compatible with the existence of two distinct processes working in parallel, namely automatic identification and structural analysis, that could either interfere or act together for the detection of differences.

Adult↗
PubMed2007

Of gnomes and leprechauns: the recruitment of recent and categorical contexts in social judgment.

Participants rated schematic faces from two categories, gnomes and leprechauns, on feature widths and pleasantness of facial configuration. Three target faces shared critical facial features across categories while two contextual faces extended the range for that category to include either very wide or very narrow features. In Experiment 1a, results indicated contextual effects on judgments of target faces when they were rated in separate categorical blocks [Wedell, D. H., & Pettibone, J. C. (1999). Preference and the contextual basis of ideals in judgment and choice. Journal of Experimental Psychology: General, 128, 346-361], but not when faces from both categories were rated together in Experiment 1b. Two additional experiments explored this failure to use categorical information. Categorical context was found to produce contrast effects on descriptive ratings of feature width when participants were forced to rely on name cues rather than actual faces in Experiment 2. In Experiment 3, both contrast effects on descriptive ratings and assimilation effects on ideals for pleasantness were found when the names for the faces were learned separately for each category. These results identify constraints on the nature of category-based stereotyping effects on judgment while isolating the influence of recent and categorical context.

Analysis of Variance↗
PubMed2005

Effects on hunger and satiety, perceived portion size and pleasantness of taste of varying the portion size of foods: a brief review of selected studies.

The portion size of foods has been identified as an important environmental factor known to affect short-term energy intake. Experiments that were conducted both in the free-living environment and in laboratory-based settings to investigate the effects of portion size on energy intake unanimously showed that as the portion size of food increased, so did subjects' energy intake. Despite the fact that the profound effects of portion size on energy intake are well documented, the mechanisms by which portion size affects energy intake are poorly understood. There is some evidence that sensory influences (e.g. visual and olfactory cues), cognitive factors (e.g. learning, social norms, monetary considerations), and post-ingestive consequences (e.g. sensations of hunger and fullness) related to the portion size of foods may interact to affect the amount of food that is consumed during a meal.

Energy Intake↗
PubMed2006

Potential of an analog scaling device for measuring fullness in children: development and preliminary testing.

Improving children's abilities to recognize when they are full is one strategy to prevent overweight, but currently, there are few validated instruments to assist this process. In the present study, we developed and tested the potential of an analog scaling device for quantifying sensations such as fullness in 4-5 year old children. The device was a picture of a doll with a rectangular stomach over which a sliding bar could be moved to communicate rated fullness levels. Eleven 4-5 year old children were shown pictures of French fries and fruit salad in five varying portion sizes that increased in diameter exponentially by a power of 1.5, ranging from 5.2 to 18.5 cm. Success in using the device was predefined as an increase in ratings as a function of increasing portion size, in at least one of two trials. Eight children were successful with the fries, and ten were successful with the fruit salad. Mean ratings across children were significantly different from each other for both foods. These data show that children can be trained to use an analog scale to quantify differences in portion sizes of foods. Future experiments will validate this scaling procedure for measuring fullness in real eating situations. If successful, this methodology might have applications to the measurement of other bodily sensations in young children.

Child, Preschool↗
PubMed2005

The coarse-to-fine hypothesis revisited: evidence from neuro-computational modeling.

The human perceptual system seems to be driven by a coarse-to-fine integration of visual information. Different results have shown a faster integration of low-spatial frequency compared with high-spatial frequency (HSF) information, starting at early retinal processes. The difference in spatial scale decomposition remains throughout the lateral geniculate nucleus (Hubel & Wiesel, 1977) and V1 (Tootell, Silverman, & De Valois, 1981). During the last decade, a debate has emerged concerning the origin of the coarse-to-fine integration. Is it a constant, perceptually driven integration (Parker et al., 1992 and Parker et al., 1996)? Instead, the flexible use hypothesis suggests that different spatial frequency channels could be enhanced depending on the requirement of the task for high-level cognitive processes like categorization (Oliva and Schyns, 1997 and Schyns and Oliva, 1999). In two connectionist simulations, we have shown that global categorization performance could actually be better performed with HSF information when the amount of information is normalized across the different spatial frequency channels. Those results suggest that high-level requirement alone could not explain the coarse-to-fine bias toward LSF information. A hypothesis is proposed concerning the possible implication of the amount of data provided by different spatial frequency channel that might provide the perceptual bias toward LSF information.

Algorithms↗
PubMed2004

Concept abstraction in the aging dog: development of a protocol using successive discrimination and size concept tasks.

The present study examined the effects of age on concept learning in beagle dogs. In experiment one, subjects were tested on a series of 2-choice size discrimination (2CSD) tasks, in which the correct response was to always approach the larger or smaller of the two blocks. Compared to old and senior dogs, young and middle-aged dogs solved the initial training subtest faster and were more successful at transferring this learning to subsequent tests. The second experiment extended the task by using three rather than two objects and introducing novel objects to test concept acquisition. Young and middle-aged dogs made fewer errors than old or senior dogs on a 3-choice size discrimination (3CSD) task. Transfer performance was above chance for all four groups on the 3CSD and first 3-choice size concept (CSC) task and for the young dogs on the second 3CSC but did not differ from the original learning criterion in any group. Age impairments in concept learning may account for differences in transfer performance on both 3CSC tests.

Age Factors↗
PubMed2006

A P300 event-related potential brain-computer interface (BCI): the effects of matrix size and inter stimulus interval on performance.

We describe a study designed to assess properties of a P300 brain-computer interface (BCI). The BCI presents the user with a matrix containing letters and numbers. The user attends to a character to be communicated and the rows and columns of the matrix briefly intensify. Each time the attended character is intensified it serves as a rare event in an oddball sequence and it elicits a P300 response. The BCI works by detecting which character elicited a P300 response. We manipulated the size of the character matrix (either 3 x 3 or 6 x 6) and the duration of the inter stimulus interval (ISI) between intensifications (either 175 or 350 ms). Online accuracy was highest for the 3 x 3 matrix 175-ms ISI condition, while bit rate was highest for the 6 x 6 matrix 175-ms ISI condition. Average accuracy in the best condition for each subject was 88%. P300 amplitude was significantly greater for the attended stimulus and for the 6 x 6 matrix. This work demonstrates that matrix size and ISI are important variables to consider when optimizing a BCI system for individual users and that a P300-BCI can be used for effective communication.

Adult↗
PubMed2005

Visual properties of objects affect manipulative forces and respiration differently.

Previously, we demonstrated that the respiratory and motor systems responded differently following consecutive lifts of an object whose weight could be altered (lighter or heavier) without changing the object's visual properties. When the weight of the object was altered in a manner unpredictable to the subject, the motor system response reflected the previous weight of the object (light or heavy) while the respiratory system reflected responses seen when lifting the heavier object regardless of whether a lighter or heavier object was lifted previously. It is possible that the default pattern of the respiratory system was due to a lack of visual size cues, which are known to have robust affects on grasp control. To test this hypothesis, 14 seated subjects performed self-initiated alternating lifts with objects whose size and weight covaried such that the weight of the upcoming lift was known despite the weight of the object previously lifted. Following both consecutive and alternating trials, the load force was scaled to the weight of the object (e.g., the heavier the object the larger the force) while the volume was scaled only following the consecutive trials. This suggests that the load forces were developed entirely based on visual information while lung volume was not. In addition, we suggest that following the consecutive trials, the volume increased as the object's weight increased in an effort to assist with trunk stabilization by indirectly increasing intra-abdominal pressure.

Adult↗
PubMed2006

Intuitive interference in quantitative reasoning.

It is well known that surface features of a task can queue multiple reasoning strategies. Interference or conflict among the strategies is signaled by increasing reaction times and error rates. To determine the neural basis of this interference, we studied 14 volunteers using event-related fMRI, as they compared the perimeters of geometrical shapes in congruent (where the shapes' perimeter changed in the same direction as its area) and incongruent (where the shapes' perimeter was conserved but its area changed) conditions. We found evidence for the engagement of bilateral parietal lobe systems during congruent trials and incorrect incongruent trials. Activation of bilateral orbital frontal cortex was evident when subjects inhibited interference associated with processing the salient feature 'area' and correctly completed the perimeters in the incongruent condition. Varying the level of interference exerted by the unattended feature 'area' (filled vs. unfilled shapes) affected the relative level of activation of right parietal regions but not orbital frontal cortex suggesting that the former is responding to the degree of facilitation while the latter is responsive to the presence of conflict (rather than the degree of conflict).

Adult↗
PubMed2006

Evoked gamma oscillations in human scalp EEG are test-retest reliable.

OBJECTIVE: Evoked, phase-locked gamma oscillations of the electroencephalogram (EEG) have been demonstrated to be modulated by both bottom-up as well as top-down factors. However, to date the test-retest reliability of these oscillations has not been studied systematically. METHODS: We recorded EEG activity of 12 healthy volunteers in response to stimuli of different sizes. Each participant took part in two sessions separated by two weeks in time. To obtain an estimate of the reliability of evoked gamma band responses (GBRs), we compared frequency and magnitude of phase-locked EEG oscillations between sessions. RESULTS: In response to large stimuli magnitude and frequency of the evoked GBR yielded significant reliability. However, this was not the case for stimuli which were too small to evoke detectable GBRs. CONCLUSIONS: The results are in accordance with studies demonstrating a dependence of gamma oscillations on stimulus parameters. SIGNIFICANCE: The current findings suggest that using appropriate stimulation, the evoked gamma response has sufficient test-retest reliability for use in assessing clinical changes in neurophysiological status.

Adult↗
PubMed2006

Adolescent development of motor imagery in a visually guided pointing task.

The development of action representation during adolescence was investigated using a visually guided pointing motor task (VGPT) to test motor imagery. Forty adolescents (24 males; mean age 13.1 years) and 33 adults (15 males; mean age 27.5 years) were instructed to both execute and imagine hand movements from a starting point to a target of varying size. Reaction time (RT) was measured for both Execution (E) and Imagery (I) conditions. There is typically a close association between time taken to execute and image actions in adults because action execution and action simulation rely on overlapping neural circuitry. Further, representations of actions are governed by the same speed-accuracy trade-off as real actions, as expressed by Fitts' Law. In the current study, performance on the VGPT in both adolescents and adults conformed to Fitts' Law in E and I conditions. However, the strength of association between E and I significantly increased with age, reflecting a refinement in action representation between adolescence and adulthood.

Adolescent↗
PubMed2004

Archer fish learn to compensate for complex optical distortions to determine the absolute size of their aerial prey.

Many animals, including humans, can visually judge the absolute size of objects regardless of changes in viewing distance and thus despite the resulting dramatic differences in the size of the actual retinal images. For animals that have to judge the size of aerial objects from underwater views, this can be a formidable problem; our calculations show that considerable and strongly viewpoint-dependent corrections are needed to compensate for the effects of light refraction. Archer fish face these optical difficulties because they have to shoot down aerial insects over a wide range of horizontal and vertical distances. We show here that these fish can learn to acquire size constancy with remarkable precision and are thus fully capable of taking complex viewpoint dependency into account. Moreover, we demonstrate that archer fish solve the problem not by interpolating within a set of stored views and distances but by learning the laws that connect apparent size with the fish's relative position to the target. This enables the fish to readily judge the absolute sizes of objects from completely novel views.

Animals↗
PubMed2004

Accuracy of estimation of large food portions.

To examine accuracy of reporting of large food portions, 50 adults were invited to eat a restaurant meal that included a hamburger patty, french fries, and ice cream. After eating, participants were asked to estimate the amount of food consumed using commonly used and larger-sized food models as a guide. With the use of commonly used models, underreporting was evident for all three foods. For example, the amount of hamburger patty consumed was on average 4.01 oz, although the average amount reported was 3.04 oz (P<.05). When larger-sized models were used, the amount reported more closely matched the amount consumed, although underreporting persisted for the hamburger patty and french fries. In summary, significant underreporting of large food portions may result when commonly used food models are used to assist individuals in reporting food portions.

Adult↗
PubMed2006

A new portion size estimation aid for wedge-shaped foods.

Dietary surveys are important for understanding food consumption patterns in national studies, clinical research, and patient counseling. Portion size estimation aids usually increase accuracy of consumers' reports of the amount of food they ate in dietary surveys. However, wedge-shaped foods (eg, pie, cake, and pizza) pose special problems; this shape is not easily estimated by previously available portion size estimation aids. In focus groups, respondents indicate they need a portion size estimation aid that is easier to use than a ruler for portion estimation of wedge-shaped foods. An adjustable wedge was developed and tested with 320 respondents, ages 18 to 65 years, of various races and education levels, and both sexes, in four states using multiple sizes and types of wedge-shaped foods. The accuracy of portion size estimation with the two portion size estimation aids was assessed. The adjustable wedge gave similar results to the ruler for most portions tested, but was more accurate (P<0.05) than the ruler in approximately one third of comparisons. Both aids resulted in substantial misestimation, indicating that regardless of aid some people have difficulty estimating portions of wedge-shaped foods. The adjustable wedge was easy for people to use and can be recommended as an option for estimating portion size of wedge-shaped foods.

Adolescent↗
PubMed2006

Portion distortion: typical portion sizes selected by young adults.

OBJECTIVE: The incidence of obesity has increased in parallel with increasing portion sizes of individually packaged and ready-to-eat prepared foods as well as foods served at restaurants. Portion distortion (perceiving large portion sizes as appropriate amounts to eat at a single eating occasion) may contribute to increasing energy intakes and expanding waistlines. The purpose of this study was to determine typical portion sizes that young adults select, how typical portion sizes compare with reference portion sizes (based in this study on the Nutrition Labeling and Education Act's quantities of food customarily eaten per eating occasion), and whether the size of typical portions has changed over time. SUBJECTS: Young adults (n=177, 75% female, age range 16 to 26 years) at a major northeastern university. METHODS: Participants served themselves typical portion sizes of eight foods at breakfast (n=63) or six foods at lunch or dinner (n=62, n=52, respectively). Typical portion-size selections were unobtrusively weighed. A unit score was calculated by awarding 1 point for each food with a typical portion size that was within 25% larger or smaller than the reference portion; larger or smaller portions were given 0 points. Thus, each participant's unit score could range from 0 to 8 at breakfast or 0 to 6 at lunch and dinner. Analysis of variance or t tests were used to determine whether typical and reference portion sizes differed, and whether typical portion sizes changed over time. RESULTS: Mean unit scores (+/-standard deviation) were 3.63+/-1.27 and 1.89+/-1.14, for breakfast and lunch/dinner, respectively, indicating little agreement between typical and reference portion sizes. Typical portions sizes in this study tended to be significantly different from those selected by young adults in a similar study conducted 2 decades ago. CONCLUSIONS: Portion distortion seems to affect the portion sizes selected by young adults for some foods. This phenomenon has the potential to hinder weight loss, weight maintenance, and/or health improvement efforts. Thus, to ensure more effective nutrition counseling, food and nutrition professionals must develop ways to "undistort" what clients perceive to be typical portion sizes and help them recognize what is an appropriate amount to eat at a single eating occasion.

Adolescent↗