Responses of motor cortex neurons of the cat to auditory stimulation and their role in the instrumental food reflex

The responses of motor cortex neurons in the cat to the presentation of a single auditory click and a series of 10 clicks presented with 1,000/sec frequency were studied under conditions of chronic experiments before and after the development of an instrumental food reflex. After reflex development a single presentation of a positive conditioned stimulus (single click) markedly influenced for 7 sec the appearance of instrumental movements. At the same time, the immediate responses of motor cortex neurons to presentation of the conditioned auditory stimulus had no impact on the appearance in the motor cortex of discharges leading to the realization of instrumental movements. Consequently, motor cortex neurons do not require activation from afferent sensory inputs for the generation of such discharges. The immediate neuronal responses to conditioned stimulation did not inhibit the realization of the instrumental reflex. It is proposed that they are associated with the realization of motor function in the unconditioned defensive response evoked by the presentation of an auditory stimulus. The presence or absence of responses to auditory conditioned stimulation was dependent upon the signal meaning of the stimulus, its physical parameters, and the degree of excitability of the animal.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 17, No. 4, pp. 539–550, July–August, 1985.     

Predator odour per se does not frighten domestic horses

Horses frequently react nervously when passing animal production farms and other places with distinctive smells, leading riders to believe that horses are innately frightened by certain odours. In three experiments, we investigated how horses respond to (1) urine from wolves and lions, (2) blood from slaughtered conspecifics and fur-derived wolf odour, and (3) a sudden auditory stimulus in either presence or absence of fur-derived wolf odour. The experiments were carried out under standardised conditions using a total of 45 naïve, 2-year-old horses. In the first two experiments we found that horses showed significant changes in behaviour (Experiments 1 and 2: increased sniffing; Experiment 2 only: increased vigilance, decreased eating, and more behavioural shifts), but no increase in heart rate compared to controls when exposed to predator odours and conspecific blood in a known test environment. However, the third experiment showed that exposure to a combination of wolf odour and a sudden stimulus (sound of a moving plastic bag) caused significantly increased heart rate responses and a tendency to a longer latency to resume feeding, compared to control horses exposed to the sudden stimulus without the wolf odour. The results indicate that predator odour per se does not frighten horses but it may cause an increased level of vigilance. The presence of predator odour may, however, cause an increased heart rate response if horses are presented to an additional fear-eliciting stimulus. This strategy may be adaptive in the wild where equids share habitats with their predators, and have to trade-off time and energy spent on anti-predation responses against time allocated to essential non-defensive activities.     

Development of infant social isolate monkeys (Macaca mulatta) in their isolation environments

This study was designed to more clearly define thetreatment of early social isolation. Four newborn infant rhesus monkeys, (Macaca mulatta) were raised in social isolation and their behavioral developmentduring their sojourn in isolation was compared to the behavioral development of four controls which were reared by mothers. The controls were matched with the isolates for age and sex and both groups were studied for 30 weeks. The following conclusions resulted from this study:

1. Infant rhesus monkeys raised in laboratory cages do not display facial expressions very frequently, whether they are isolate-reared or alone with a mother. A search of the literature indicated that facial expressions do not occur frequently early in life even when peers are provided.
2. Isolates spent more time looking at human observers, at the nonsocial environment, and at themselves than did controls while controls looked a their mothers or slept.
3. Isolates showed more walking and more manual exploration of the cage and of themselves than did controls but controls did more cage climbing and jumping, and the latter was often oriented toward the mother. The isolates moved more slowly and awkwardly than did the controls.
4. Isolates did not make as extensive use of towels in their cages as we had expected. Controls were in contact with their mothers much more frequently than isolates were in contact with their towels.
5. Abnormal movements such as rocking, self-grasping, and autoeroticism, appeared in the isolates before the end of thefirst month. Thus, the first month of life is evidently extremely crucial for the development of abnormal behavior. Though many abnormal movements first appear during the first month, each individual isolate apparently does not settle down to his own favorite type of weirdness until well after seven months of age.

     

The effects of prenatal PCBs on adult social behavior in rats

Endocrine disrupting chemical (EDC) exposures during critical periods of development may influence neuronal development and the manifestation of sexually dimorphic sociability and social novelty behaviors in adulthood. In this study, we assessed the effects of gestational exposure to PCBs on the social behavior of males and females later in adulthood. A weakly estrogenic PCB mixture, Aroclor 1221 (A1221, 0.5 or 1 mg/kg) was administered to pregnant Sprague–Dawley rat dams. Both a positive control (estradiol benzoate; EB, 50 μg/kg) and negative control (dimethylsulfoxide; DMSO in sesame oil vehicle) were similarly administered to separate sets of dams. The sexes responded differently in two tasks essential to sociality. Using a three-chamber apparatus that contained a caged, same-sex, gonadectomized stimulus animal and an empty stimulus cage, we found that both sexes showed a strong preference for affiliating with a stimulus animal (vs. an empty cage), an effect that was much more pronounced in the males. In the second task, a novel and a familiar stimulus animal were caged at opposite ends of the same apparatus. Females displayed a higher degree of novelty preference than the males. During both tests, females had significantly higher social approach behaviors while male engaged in significantly more interactive behaviors with the conspecific. Of particular interest, males born of dams that received prenatal A1221 (0.5 mg/kg) exhibited an overall decrease in nose-to-nose investigations. These behavioral data suggest that the males are more sensitive to A1221 treatment than are females. In addition to behavioral analysis, serum corticosterone was measured. Females born of dams treated with A1221 (0.5 mg/kg) had significantly higher concentrations of corticosterone than the DMSO female group; males were unaffected. Females also had significantly higher corticosterone concentrations than did males. Overall, our results suggest that the effects of gestational exposure to PCBs on adult social behavior are relatively limited within this particular paradigm.     

Automated auditory recognition training and testing

Laboratory training and testing of auditory recognition skills in animals is important for understanding animal communication systems that depend on auditory cues. Songbirds are commonly studied because of their exceptional ability to learn complex vocalizations. In recent years, mounting interest in the perceptual abilities of songbirds has increased the demand for laboratory behavioural training and testing paradigms. Here, we describe and demonstrate the success of a method for auditory discrimination experiments, including all the necessary hardware, training procedures and freely-available, versatile software. The system can run several behavioural training and testing paradigms, including operant (go-nogo, stimulus preference, and two-alternative forced choice) and classical conditioning tasks. The software and some hardware components can be used with any laboratory animal that learns and responds to sensory cues. The peripheral hardware and training procedures are designed for use with songbirds and auditory stimuli. Using the go-nogo paradigm of the training system, we show that adult zebra finches learn to recognize and correctly classify individual female calls and male songs. We also show that learning the task generalizes to new stimulus classes; birds that learned the task with calls subsequently learned to recognize songs faster than did birds that learned the task and songs at the same time.     

Immunological reactivity of tuberculosis patients

Summary The investigation made byWilkens andTasman (1959) into the immunization of tuberculosis patients with Tetanus Phosphate Toxoid has been extended to a further group of patients and control subjects. The work described here covered a total of 29 controls and 54 tuberculosis patients; the latter were from two different clinics (SAZU and “Zonnegloren”). On the whole, the results previously reported byWilkens andTasman were comfirmed in that tuberculosis patients were found to respond to primary immunization with Tetanus-P.T. (2 injections of 0.5 ml at a one-month interval) by a less marked and slower antitoxin production than the normal controls. The patients treated at SAZU showed a more deviant behaviour in this respect, than did the “Zonnegloren” patients. A number of specifically designed animal experiments showed that administration of PAS had an unfavourable effect on development of immunity after the first P.T. injection. This fact might possibly explain the behaviour seen in the tuberculosis patients. It might also explain the marked difference in immunological reactivity between the SAZU and the “Zonnegloren” patients, because the former chiefly received this agent by intravenous drip, while the latter were given oral medication. It is possible that intravenous administration of PAS produces higher blood concentrations than oral administration.     

Vocal buffering of the stress response: exposure to conspecific vocalizations moderates urinary cortisol excretion in isolated marmosets

For many species, the presence of a significant social partner can lessen the behavioral and physiological responses to stressful stimuli. This study examined whether a single, individually specific, signature vocalization (phee call) could attenuate the physiological stress response that is induced in marmosets by housing them in short-term social isolation. Utilizing a repeated-measures design, adult marmosets (n=10) were temporarily isolated from their long-term pair mate and exposed to three conditions: signature vocalizations from the pair mate, phee calls from an unfamiliar opposite sex individual, or no auditory stimuli. Levels of urinary cortisol were monitored as a physiological indicator of the stress response. Urinary cortisol levels were also monitored, while subjects remained undisturbed in their home cages to provide baseline levels. Temporarily isolated marmosets showed significantly higher levels of urinary cortisol than undisturbed marmosets. However, the nature of the acoustic stimulus experienced during isolation led to differences in the excretion of urinary cortisol. Isolated marmosets exposed to a familiar pair mate's vocalization showed significantly lower levels of urinary cortisol than when exposed to unfamiliar marmoset vocalizations (P <0.04) or to no auditory stimuli (P <0.03). Neither the duration of pairing nor the quality of relationship in the pair (indexed by spatial proximity scores) predicted the magnitude of reduction in cortisol in the familiar vocalization condition. The results presented here provide the first evidence that a single, individually specific communication signal can decrease the magnitude of a physiological stress response in a manner analogous to the physical presence of a social partner, a process we term "vocal buffering."     

Sound the alarm: learned association of predation risk with novel auditory stimuli by fathead minnows ( Pimephales promelas ) and glowlight tetras ( Hemigrammus erythrozonus ) after single simultaneous pairings with conspecific chemical alarm cues

Fathead minnows, Pimephales promelas, and glowlight tetras, Hemigrammus erythrozonus, were tested for their ability to associate predation risk with novel auditory stimuli after auditory stimuli were presented simultaneously with chemical alarm cues. Minnows and tetras gave a fright response when exposed to skin extract (alarm cue) and an artificial auditory sound stimulus, but no response to water (control) and sound, indicating that they did not have a pre-existing aversion to the auditory stimulus. When retested with sound stimuli alone, minnows and glowlight tetras that had previously been conditioned with water and sound showed no response, but those that had been conditioned with alarm cues and sound exhibited antipredator behaviour (reduced activity) in response to the auditory cue. This is the first known demonstration of learned association of an auditory cue with predation risk, and raises questions about the role of sound in mediating predator-prey interactions in fishes.     

Comparing the relative benefits of grooming-contact and full-contact pairing for laboratory-housed adult female Macaca fascicularis

Tactile social contact is the most effective form of environmental enrichment for promoting normal behavior in captive primates. For laboratory macaques housed indoors, pair housing is the most common method for socialization. Pairs can be housed either in full contact (FC), or in protected contact (PC). At Washington National Primate Research Center, PC is provided by grooming-contact (GC) cages whereby two partners are housed individually in adjacent cages with access to each other through widely spaced vertical bars. Grooming-contact has been used to accommodate research protocol restrictions and improve the likelihood of compatibility for various pairings, in part by enabling male-female pairs. This study compares the benefits between the two housing types by video recording 14 pairs of adult female Macaca fascicularis in four sequential housing phases following an ABBA design: baseline grooming-contact, full contact shortly after introduction, 1-month-later full contact, and after reversion to grooming-contact. Prior to this study, pairs had been housed compatibly in GC. Twelve of the 14 long-term pairs transitioned successfully to full contact and data presented exclude the two failed pairs. Allogrooming increased significantly when pairs first switched from GC to FC (P = 0.018), but the effect did not last through the on 1-month-later FC phase suggesting that the initial improvement in affiliative behavior was a transitory novelty response that did not persist. Self-grooming significantly decreased between the first GC and first FC phases (P = 0.016), likely due to redirected allogrooming. Non-contact affiliative behavior towards partner or other conspecifics in the room did not differ, nor did agonism towards partner or others in the room. Occurrence of abnormal, tension, manipulation, miscellaneous active, and inactive behaviors did not differ significantly across housing phases. Proximity measurements indicated that pairs were significantly out of arm's reach more often in protected contact than when in full contact (P ≤ 0.02). Proportion of time spent in physical contact significantly increased between the first GC and first FC phases (P = 0.002), but subsequently declined. For both FC phases, partners chose to spend about 50% of their time in the same cage. Few behavioral improvements were seen after pairs switched to full contact and no negative effects came of reversion to grooming contact. This study suggests that tactile contact provided through widely spaced bars (grooming-contact) is a viable alternative to full contact housing for adult female longtailed macaques. It provides a degree of social housing while allowing both partners choice and control, key concepts in contemporary animal welfare guidelines.     

Pigeons' timing of an arbitrary and a naturalistic auditory stimulus: tone versus cooing

Previous animal research has traditionally used arbitrary stimuli to investigate timing in a temporal bisection procedure. The current study compared the timing of the duration of an arbitrary, auditory stimulus (a 500-Hz tone) to the timing of the duration of a naturalistic, auditory stimulus (a pigeon cooing). In the first phase of this study, temporal perception was assessed by comparing psychophysical functions for the duration of tone and cooing signals. In the first set of tests, the point of subjective equality (PSE) was significantly lower for the tone than for the cooing stimulus, indicating that tones were judged longer than equivalent durations of cooing. In the second set of tests, gaps were introduced in the tone signal to match those present in the cooing signal, and no significant difference in the PSE for the tone or the cooing signal was found. A repetition of the testing conducted with gaps removed from the tone signal, failed to replicate the difference in the PSEs for the tone and cooing signals originally obtained. In the second phase of the study, memory for the duration of tone and cooing was examined, and a choose-long bias was found for both signals. Based on these results, it appears that, for pigeons, there may be no significant differences in either temporal perception or temporal memory for arbitrary, auditory signals and more complex, naturalistic, auditory signals.     

Response to novel housing in two groups of captive tufted capuchin monkeys (Cebus apella)

The influence of age, maternal status, and the presence of a group male on use of space was assessed in two groups of captive tufted capuchin monkeys that underwent a move from indoor housing to a larger outdoor facility. Both groups originally contained two adult males, but only one group retained a male after the move. Following the move, mothers spent less time on the ground when carrying their infants than they did when not carrying their infants. In the group with no male (1) individuals decreased time spent on the ground relative to pre-move levels, whereas no such difference was noted in the group with the male; (2) females spent more time carrying their infants than did females in the group with a male. In the group with the adult male, juveniles spent less time on the ground than did non-mother adult females, whereas no difference had existed prior to the move. Grooming rates dropped from pre-move to post-move, but the mean number of partners with which each animal was in contact increased. Measures of social behavior varied across post-move observation periods inversely to time spent on the ground. These results are consistent with the view that an individual's relative vulnerability influences behavioral conservatism in novel environments, and suggests a relatively profound role for males in promoting exploration of new space in this species.     

The social interactions of adult conspecifics with an adult XY gonadal dysgenetic chacma baboon (Papio ursinus)

Two separate behavioral studies on an XY gonadal dysgenetic chacma baboon were carried out. In the first experiment the focal subject was treated identically as the control females by her adult male test partners. In contrast to the controls in this experiment the dysgenetic animal reciprocated the agonistic behaviors directed by the males toward her. In the second study intact and castrated males as well as ovariectomized females served as controls for the dysgenetic subject in tests with ovariectomized adult females. The stimulus females presented more to both classes of males than either the subject females or the gonadal dysgenetic individual, suggesting that the focal subject was treated by other female conspecifics as a female.     

Effects of Pair-Bond and Social Context on Male–Female Interactions in Captive Titi Monkeys (Callicebus moloch, Primates: Cebidae)

In monogamous species, an abiding relationship between a specific adult male and a specific adult female is a defining feature of the social system. The interactions between these individuals are influenced by many factors, including not only the history of their relationship (for example, development of a mutual bond), but also the immediate effects of the prevailing social context (for example, presence and sex of extra‐pair conspecifics). In this study we examined the effects of an existing bond and of social context on interactions between adult heterosexual pairs of the monogamous titi monkeys (Callicebus moloch). Twelve adult males and 12 adult females were tested with their cagemates and with an unfamiliar partner of the opposite sex in five social contexts: (1) mated male–female pair; (2) unfamiliar pair; (3) single female; (4) single male; and (5) empty stimulus cage. Results show that mated pairs were more affiliative than unfamiliar pairs and differentiated social contexts more sharply. Males were more responsive to context than females. Distance between mates was less and physical contact was more frequent in the presence of male–female pairs or a single male, than in the presence of a single female or an empty cage. These findings suggest that the presence and sex of strangers have a stronger influence on male–female interactions when the pair has an existing relationship.     

Risk assessment and avoidance in juvenile golden hamsters exposed to repeated stress

Juvenile hamsters are typically less vulnerable to social subjugation than adults, although they will avoid aggressive individuals in some situations. The purpose of this study was to determine the extent to which social subjugation stimulates fear- or anxiety-like behavior in juvenile hamsters in both social and non-social contexts. Social context testing was conducted in a Y-maze while the non-social context apparatus consisted of an open field arena and a lat-maze. In the Y-maze, subjects were exposed to an unfamiliar aggressive adult hamster. Compared with non-subjugated controls, subjugated juveniles spent significantly more time in the area furthest from the aggressive adult stimulus. In addition, socially stressed animals were more likely to avoid the arm of the maze containing the social stimulus. When they did walk in the arm containing the social stimulus, subjugated individuals were more likely to ambulate slowly. Subjugated hamsters also performed fewer olfactory investigations in the proximity of the unfamiliar aggressive individual. Despite these behavioral differences detected between groups during testing in a social context, we observed no differences between groups in the open field and lat-maze. This suggests that the effects of subjugation observed in the Y-maze are specific to exposure to a social context and that social subjugation in juvenile hamsters does not result in a generalized state of fear. Instead, subjugated juveniles learned to avoid adult males and were otherwise behaviorally similar to non-subjugated controls.     

Prenatal diet determines susceptibility to cardiac ischaemia-reperfusion injury following treatment with diethylmaleic acid and N-acetylcysteine

Fetal undernutrition programmes increased risk of developing cardiovascular disease in adult life. We hypothesized that prenatal protein restriction would impair recovery in post-ischaemic cardiac function in adult offspring through antioxidant-mediated processes. Pregnant Wistar rats were fed control or maternal low protein diets (MLP) throughout gestation. The offspring of these rats were treated with either saline, N-acetylcysteine (NAC), diethylmaleate (DEM), or both NAC and DEM to manipulate glutathione status at 6 months of age. Hearts were rapidly excised and retro-perfused (Langendorff) to assess isolated cardiac function before (baseline), and during 30 min global ischaemia and 60 min reperfusion. Hearts from adult rats exposed to a MLP diet in utero suffered greater cardiac dysfunction than those from controls following 30 min ischaemia. Left ventricular developed pressure (LVDP) was significantly reduced upon early reperfusion (p<0.042) in MLP rats compared to controls. NAC pre-treatment had no effect on LVDP of hearts from control animal hearts but improved the revival of MLP hearts to the same level as controls. DEM treatment did not affect control hearts but significantly reduced recovery of LVDP of MLP hearts during early (p<0.008) and late reperfusion (0.035). Combined NAC and DEM treatment had no effect on LVDP between control and MLP fed offspring. Prenatal protein restriction throughout pregnancy increases the susceptibility of the adult rat heart to suffer a functional deficit following ischaemia-reperfusion injury. Pharmacologically improving antioxidant status prevented this injury. A nutritionally-imbalanced developmental environment may increase susceptibility to coronary heart disease through the programming of myocardial glutathione metabolism.     

Experimental infections of free-ranging Rocky Mountain bighorn sheep with lungworms (Protostrongylus spp.; Nematoda: Protostrongylidae)

Twelve free-ranging Rocky Mountain bighorn lambs (Ovis canadensis canadensis), each exposed experimentally to 125-1,000 infective third-stage larvae of Protostrongylus stilesi and P. rushi, shed significantly more first-stage larvae in their feces than did control lambs, but showed no clinical signs of illness and had equivalent summer and overwinter survival as control lambs. Two adult ewes, each exposed to 925 infective larvae, showed no increase in numbers of first-stage larvae in their feces; both survived at least 14 mo postexposure. Experimentally exposed lambs did not differ from control lambs in numbers of larvae in their feces in the following summer. Three experimental lambs had 313-402 adult P. stilesi and 0-97 adult P. rushi on necropsy; two control lambs had 255 and 270 P. stilesi and no P. rushi. The presence of these numbers of lungworms did not appear to be sufficient to precipitate lungworm pneumonia in bighorn lambs under the conditions of this study.     

Effects of early rearing experience on subsequent adult sexual behavior using domestic cats (Felis catus) as a model for exotic small felids

Zoo professionals generally believe that maternal rearing of zoo animals is preferable to human/nursery raising. The lack of consistent reproductive success in small captive exotic felids has been partially attributed to an excess of human-raised individuals. To investigate experimentally the effects of human/nursery rearing on adult sexual behavior, domestic cats were used as a model for small captive exotic felids. Three groups of female domestic cats were reared under three different conditions (intended to mimic typical zoo rearing situations) and then paired at sexual maturity with sexually experienced males. Cats in Condition 1 were Human-Raised Alone, i.e., had no physical or visual contact with con-specifics until sexual maturity; cats in Condition II were Human-Raised with a Sibling, i.e., had no physical or visual contact with any conspecifics except their respective sibling until sexual maturity; cats in Condition 3 were Maternally Raised with a female sibling, but had no other physical or visual contact with other conspecifics until sexual maturity. Individuals in Condition 3 copulated significantly more often than did the individuals in Condition 1. The individuals in Condition 1 were distinguished by the extreme aggression they displayed toward both the males with which they were paired and their human-caretakers. Data suggest that human-reared female cats are less likely to reproduce than are their maternally-reared counterparts. These results suggest that, whenever possible, nursery-raising of small exotic felids should be avoided.     

Selenium and <Emphasis Type="SmallCaps">l</Emphasis>-Carnitine Reduce Oxidative Stress in the Heart of Rat Induced by 2.45-GHz Radiation from Wireless Devices

The aim of this study was to investigate the possible protective role of selenium and l-carnitine on oxidative stress induced by 2.45-GHz radiation in heart of rat. For this purpose, 30 male Wistar Albino rats were equally divided into five groups namely controls, sham controls, radiation-exposed rats, radiation-exposed rats treated with intraperitoneal injections of sodium selenite at a dose of 1.5 mg/kg/day, and radiation-exposed rats treated with intraperitoneal injections of l-carnitine at a dose of 1.5 mg/kg/day. Except for the controls and sham controls, the animals were exposed to 2.45-GHz radiation during 60 min/day for 28 days. The lipid peroxidation (LP) levels were higher in the radiation-exposed groups than in the control and sham control groups. The lipid peroxidation level in the irradiated animals treated with selenium and l-carnitine was lower than in those that were only exposed to 2.45-GHz radiation. The concentrations of vitamins A, C, and E were lower in the irradiated-only group relative to control and sham control groups, but their concentrations were increased in the groups treated with selenium- and l-carnitine. The activity of glutathione peroxidase was higher in the selenium-treated group than in the animals that were irradiated but received no treatment. The erythrocyte-reduced glutathione and β-carotene concentrations did not change in any of the groups. In conclusion, 2.45-GHz electromagnetic radiation caused oxidative stress in the heart of rats. There is an apparent protective effect of selenium and l-carnitine by inhibition of free radical formation and support of the antioxidant redox system.     

Supply-side control over the survivorship of Chthamalus spp. recruits in northern Baja California

The constant supply of larvae to coastal habitats is important for the persistence of populations and can vary depending on oceanic conditions that may affect physical transport processes. We evaluated the survivorship of Chthamalus recruits in Playa San Miguel, Baja California, for over a year to evaluate if the supply of new recruits was of greater importance than the post-recruitment factors of competition and predation in determining adult population size. We hypothesized that the number of Chthamalus recruits would predict the number of adults present and that predation and competition would not play a significant role in determining adult densities. Recruit density was a robust predictor of adult density despite the presence of weak density-dependent mortality. Neither predation nor competition significantly affected the survivorship of recruits and did not decouple the relationship between recruit and adult densities, suggesting that these post-recruitment controls did not play an important role in determining the population size of Chthamalus barnacles at this site. The data support the hypothesis that supply-side control is the primary factor structuring the population of Chthamalus in the intertidal community at Playa San Miguel.     

Patients' Attitudes to Medical Students in General Practice

259 consecutive adult patients were interviewed regarding their attitudes to the presence of medical students at consultation, at examination, and at home visits. Few patients declared reluctance to discussing physical illness and smoking or drinking problems in the student''s presence, but many had appreciable inhibitions about discussing almost every other common component of consultation. Over half of the younger women interviewed would prefer students not to be present at physical or pelvic examination.Neither age nor social class showed significant association with declared preference, but previous contact with students did not decrease inhibitions among patients. Only 15% of respondents said that they would be more upset by the presence of two students rather than one.