The pigeon's variability discrimination with lists of successively presented visual stimuli.

Pigeons previously trained to peck 1 button (same) after the successive presentation of 16 identical pictures and to peck a 2nd button (different) after the successive presentation of 16 nonidentical pictures were tested on lists involving different degrees of variability, different list lengths, and different temporal organizations of list items. The pigeons' performances on this successive same-different task revealed a strong sensitivity to list entropy; but, their discrimination was also affected by their memory for list items and by the accumulated evidence for a same versus a different response. Statistical models confirmed and quantified the importance of these additional factors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The what and the where of the pigeon's processing of complex visual stimuli.

Eight pigeons were trained on a go-no go visual discrimination involving I S+ and 15 S–s. The 16 discriminative stimuli were black-and-white line drawings created by the factorial combination of 4 different geometric shapes (wedge, cylinder, cone, handle) in 4 different spatial locations (right, left, above, below) in relation to a common shape (cube). All of the pigeons readily learned this complex visual discrimination. Each bird's pecking behavior was controlled by both attributes of the line drawings, but somewhat stronger stimulus control was exerted by the location of the added component than by its shape. Across all 8 pigeons, there was an inverse relation between stimulus control by component shape and component location. These results document pigeons' joint processing of "what" and "where" information in visual discrimination learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of number of items on the pigeon's discrimination of same from different visual displays.

The pigeon's discrimination of visual displays comprising from 2 to 16 computer icons that were either the same as or different from one another was studied. Discrimination of Same from Different displays improved when the displays contained more icons, both after training with just 16-icon displays (Experiment 1) and after training with 2-, 4-, 8-, 12-, and 16-icon displays (Experiment 2). That improvement was specific to displays of different icons; accuracy to displays of same icons did not differ as a function of icon number. These results were well described by the degree of variability or entropy in multielement visual displays. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The pigeon's recognition of drawings of depth-rotated stimuli.

Four experiments used a 4-choice discrimination learning paradigm to explore the pigeon's recognition of line drawings of 4 objects (an airplane, a chair, a desk lamp, and a flashlight) that were rotated in depth. The pigeons reliably generalized discriminative responding to pictorial stimuli over all untrained depth rotations, despite the birds' having been trained at only a single depth orientation. These generalization gradients closely resembled those found in prior research that used other stimulus dimensions. Increasing the number of different vantage points in the training set from 1 to 3 broadened the range of generalized testing performance, with wider spacing of the training orientations more effectively broadening generalized responding. Template and geon theories of visual recognition are applied to these empirical results. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Individual differences in spatial organization of cortical electrical activity during formation of a set to visual stimuli

Vascular affections of the brain remain a formidable psychiatric challenge nowadays. According to WHO reports cerebrovascular disorders constitute one of the three chief causes of mortality in the population of the economically developed countries of the world. The most important cause of vascular psychoses is considered to be atherosclerosis and hypertensive disease. Today vascular psychoses have become a most common type of abnormal mental states in young adults (greater then 30-40 years old). The studies made have yielded evidence in support of the psychoses morbidity to be dependent upon particular season of year as well as on the climatic features of the locality. Natural factors have been found out to affect the prevalence of vascular psychoses in Chernivtsi Province. The findings obtained suggest to us a substantial prevalence of atherosclerotic and hypertensive psychoses in the plains-men living under conditions of a mild climate.     

Numerosity discrimination of repetitive visual stimuli by mildly retarded adolescents and normal children.

Compared 20 male and 20 female retarded adolescents with 40 younger normals matched for sex and ma on a visual numerosity task. Sequential light flashes of 300, 500, and 700 msec. Occurring in multiple loci were presented in trains of 3-38 flashes. Error frequency and magnitude scores were significantly (p     

Conditioning to complex stimuli.

A research program is described dealing with behavior in a classical GSR conditioning situation. The empirical program is related "to the broader perspective of psychology in general." The research "affords a slim—but I hope stable—bridge between S-R learning theory and whatever is meant by perceptual theory." A rationale of assumptions is developed and on the basis of analysis predictions are formulated. "The present results are eminently consonant with an S-S interpretation of behavior… though I have attempted to make it consonant with S-R contiguity theory by employing the notion of internalized stimuli generated by responses to the conditioned stimulus." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cardiac and visual responses to stimuli presented both foveally and peripherally as a function of moving stimuli.

Measured heart rate (HR) and visual fixation responses as indices of attention getting (AG) and attention holding (AH) in 17 15-wk-old infants. The stimulus situation was one in which a brief central stimulus was followed by either a brief peripheral stimulus (AG trials) or a prolonged peripheral stimulus (AH trials). The stimuli for both central and peripheral presentations were moving black and white bar patterns. The speed for the central stimulus was constant over trials and groups (at 6.6°/sec), whereas the peripheral stimuli were either 6.6 or 26°/sec. Results suggest that much of the observed HR change can be accounted for by the AG phase, whereas the AH phase was reflected in the time it took for the cardiac responses to return to prestimulus baseline values. Stimulus speed also affected both attention behaviors; the faster speed produced the greatest HR change. Latency of 1st fixation and duration of looking measures did not show any discrimination between stimuli of different speeds. (12 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modification of the pigeon's visual startle reaction by the sensory environment.

Seven experiments related amplitude and latency of 20 racing pigeons' startle response, elicited by an intense visual stimulus, to antecedent auditory and visual events in the sensory environment. Data indicate that (a) within broad limits the amplitude of the reflex was a positive function of the intensity of the sensory background prevailing at the time of startle elicitation; (b) a change in the sensory environment occurring 15-2,000 msec prior to the startle-eliciting stimulus inhibited the amplitude of the response; and (c) a change in the sensory environment less than 10 msec prior to the startle-eliciting stimulus reduced the latency of the response. Findings are consistent with previous research on acoustic elicited startle in the rat. The overall configuration of the results suggests that a pathway including the reticulospinal tract and the bulbopontine reticular nuclei could be the major mediator of startle. In these terms, latency-reduction effects would occur because of partial activation of this pathway, amplitude inhibition would occur because of cerebellar influence, and amplitude facilitation would reflect cerebral or striatal influences. (49 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of spatial separation and similarity of stimuli on discrimination learning of children and adults.

32 females and 32 males from each of 3 levels-kindergarten, 2nd grade, and college-were given a 2-choice simultaneous discrimination task in which the stimuli were separated either by 6.35 or 25.4 cm. 2 levels of stimulus similarity were used. Increasing the distance between stimuli interfered with the learning of all age groups when the stimuli were highly similar. When stimuli were less similar, however, increasing the interstimulus distance retarded learning in children but not in adults. Results are consistent with findings that spatial separation of task components in a variety of situations interferes more with the performance of children than with that of adults. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Entropy and variability discrimination.

Two experiments examined college students' discrimination of complex visual displays that involved different degrees of variability of "entropy." Displays depicted 16 black and white line drawings of various types (e.g., a brain, a clock, a hand); the participants were required to classify a display in terms of its variability (e.g., low-variability display contains many identical items, whereas a high-variability display contains few identical items). The participants' accuracy and reaction time scores on a 2-alternative forced-choice discrimination disclosed that people can and do use entropy to classify different levels of visual display variability. Individuals differed in their use of absolute rather than relative entropy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pigeons show same-different conceptualization after training with complex visual stimuli.

Eight pigeons were first trained to peck 1 button in the presence of 16 distinct 4?×?4 arrays of identical pictures and to peck a 2nd button in the presence of 16 distinct 4?×?4 arrays of nonidentical pictures. Later, they were tested with 16 other same and 16 other different stimulus arrays involving untrained pictures. Performance to the testing arrays greatly exceeded chance levels, thus suggesting same-different conceptualization by pigeons. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A comparison of discrimination and reversal learning for olfactory and visual stimuli in aged rats.

The present study investigated age-related differences in discrimination and reversal learning for olfactory and visual stimuli in 6-month and 24-month-old rats. Rats were trained to discriminate between two pseudo-randomly selected odors or objects. Once each animal reached a criterion on discrimination trials, the reward contingencies were reversed. Young and aged rats acquired the olfactory and visual discrimination tasks at similar rates. However, on reversal trials, aged rats required significantly more trials to reach the learning criterion on both the olfactory and visual reversal tasks than young rats. The deficit in reversal learning was comparable for odors and objects. Furthermore, the results showed that rats acquired the olfactory task more readily than the visual task. The present study represents the first examination of age-related differences in reversal learning using the same paradigm for odors and objects to facilitate cross-modal comparisons. The results may have important implications for the selection of memory paradigms for future research studies on aging. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Habituation to complex emotional stimuli.

On each of 3 sessions, 45 male undergraduates viewed 20 presentations of an isolated accident (experimental group) and 23 Ss viewed a benign (control group) motion picture scene. At the end of each session, Ss also saw the complete movie from which these scenes were taken. Skin conductance, self-reported distress, and, to a lesser extent, heart rate showed considerable carry-over of habituation from the accident scene, viewed in isolation, to the same scene embedded in the complete movie. There was, however, very little generalization of habituation to other, similar accident scenes in the same movie. Heart rate response to the isolated accident scene was primarily deceleration, while cardiac acceleration was the primary response when the accident scene was viewed in the context of the complete film. The implication of these results for analogue studies of desensitization therapy is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modeling spatial integration and contrast invariance in visual pattern discrimination

PURPOSE: Human pattern discrimination performance has been reported to be largely independent of stimulus contrast but to depend on stimulus area. The authors propose a model that combines the effects of spatial integration and contrast. The model is based on the computation of similarity between pattern templates in memory and signals to be discriminated using normalized correlation. There are also two sources of additive noise, one before and one after the computation of correlation. The model was compared with human observers in an orientation discrimination task. METHODS: Orientation discrimination thresholds of human observers were measured for sinusoidal gratings of various areas, contrasts, and spatial frequencies. A two-interval, forced-choice methods was used. The performance of the model was determined by using computer simulations. RESULTS: It was found that the effects of contrast and grating area were interrelated. The decrease of orientation thresholds as a function of grating area was considerably larger at low than at high contrast. On the other hand, orientation thresholds decreased clearly as a function of contrast at the smallest grating areas but hardly at all at the largest grating areas. The model accounted well for the experimental findings. CONCLUSIONS: Because the invariance of orientation discrimination with respect to stimulus contrast depended on area, the cause of the invariance appeared to occur after spatial integration. The model explains this so that, with increasing contrast or area, the normalized correlation gradually approached a constant value. The proportion of pretemplate noise became negligible compared to the constant posttemplate noise. Thus, total noise also approached a constant value. Hence, the signal-to-noise ratio and discrimination performance became constant.     

Display duration and stereoscopic depth discrimination.

Investigated the role of display duration in stereoscopic depth perception. The display consisted of a dynamic random-dot stereogram, with 2 disparity defined squares, one on the left and one on the right of a central (Nonius) fixation stimulus. The sign of the disparity (crossed or uncrossed) was always the same for both squares, and the magnitude of disparity was 0.25° for one square and either 0.125° or 0.375° for the other square. 100 participants (aged 18–43 yrs) indicated which square appeared closer. The display duration was varied adaptively between 20 and 1000 ms until participants performed at 75% accuracy. Results confirmed large individual differences in the display duration required for stereoscopic depth perception. Approximately half of the participants were able to perform the task at 20 ms, while the remaining participants required up to 1000 ms to perform at criterion. The present study shows that display duration is a critical variable in explaining wide differences in reported abilities of individuals to process stereoscopic depth information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Verbal discrimination of pleasant and unpleasant stimuli prior to specific identification.

"The present study investigated the capacity of human Ss to judge the emotional quality of stimuli presented too briefly [tachistoscopically] and at illumination levels too low for correct specific identification… . After the exposure of each word, the Ss were required to judge whether the word was pleasant or unpleasant as well as to guess what the word was… . the results revealed that in the absence of specific recognition or identification of the stimuli, the Ss' affective judgments were more often correct than could be attributed to chance." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Distance and the presentation of visual stimuli to birds

Hemodynamic factors have profound influences on blood vessels. To test the hypothesis that hemodynamic conditions modify the pattern of remodeling in response to injury, monocrotaline (MCT) injury in Sprague-Dawley rats was followed 1 week later by left pneumonectomy to increase blood flow to the right lung. Right pulmonary artery remodeling in these MCT plus pneumonectomy animals was compared with animals receiving MCT or pneumonectomy alone. Neointimal changes developed in more than 90% of all right lung intra-acinar vessels 5 weeks after MCT injury (4 weeks after pneumonectomy). Neointimal lesions did not develop in untreated animals or in animals receiving MCT or pneumonectomy only. Animals with a neointimal pattern of remodeling developed severe right ventricular hypertrophy (RVH) whereas animals with a medial hypertrophy pattern of remodeling (MCT only) developed moderate RVH compared with control animals. Neointimal lesions and RVH were similar whether injury preceded pneumonectomy or vice versa. To exclude the possibility that neointimal lesions resulted from injury plus post-pneumonectomy compensatory lung growth, rather than injury plus increased flow, a left subclavian-pulmonary artery anastomosis was substituted for pneumonectomy. Neointimal lesions and severe RVH developed in these animals but were not seen in animals receiving either MCT or anastomosis only. These studies demonstrate an important role for hemodynamics in determining the pattern of pulmonary vascular remodeling after injury.     

Race as a visual feature: Using visual search and perceptual discrimination tasks to understand face categories and the cross-race recognition deficit.

One of the most familiar empirical phenomena associated with face recognition is the cross-race (CR) recognition deficit whereby people have difficulty recognizing members of a race different from their own. Most researchers assume that the CR deficit is caused by failure to generalize perceptual encoding expertise from same-race (SR) faces to CR faces. However, this explanation ignores critical differences in the social cognitions and feature coding priorities associated with SR and CR faces. On the basis of data from visual search and perceptual discrimination tasks, it appears that the deficit occurs because people emphasize visual information specifying race at the expense of individuating information when recognizing CR faces. In particular, it is possible to observe a paradoxical improvement in both detection and perceptual discrimination accuracy for CR faces that is limited to those who recognize them poorly. These findings support a new explanation for the CR recognition deficit based on feature coding differences between CR and SR faces, and appear incompatible with similarity-based models of face categories. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Number and position of visual stimuli as determinants of reaction time in schizophrenia.

Notes that RT in normal Ss has been shown to be linearly related to stimulus complexity, defined as the log of the number of equally probable stimuli to which a response may be made. Data from an earlier study of 40 short- and long-term paranoid and nonparanoid male schizophrenics and 10 male hospital employees were reanalyzed and compared with P. Venable's (see record 1959-10789-001) study of schizophrenic deficit. Although experimental procedures were dissimilar, both studies found that increased complexity did not result in schizophrenics having steeper regression slopes than normal Ss. Consideration of the position of the critical stimulus, however, clearly indicated that long-term, nonparanoid schizophrenics narrow attention to central cues when confronted by an increase in complexity. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)