Sound localization in a predatory rodent, the northern grasshopper mouse (Onychomys leucogaster)

A comparison of the ability of mammals to localize sound revealed that among the animals examined to date, none of the rodents have been able to localize as accurately as the carnivores. Because all of these rodents are prey animals, the question arises as to whether their poor localization acuity is a phyletic trait of Rodentia or whether it is a trait common to prey species that may be under less selective pressure than predators to localize sound accurately. To answer this question, sound localization acuity was determined in a species that is both predatory and a rodent, the northern grasshopper mouse. Localization thresholds for a single 100-ms noise burst were determined for three grasshopper mice using a conditioned avoidance procedure. Their 50% discrimination threshold of 19 degrees is larger than that of any of the previously tested carnivores and well within the range of other rodents. However, calculations of the binaural sound localization cues available to rodents (based on their head size) suggest that the grasshopper mouse may make more efficient use of the available locus cues than other rodents. Thus, although the grasshopper mouse cannot localize as accurately as carnivores, it appears to be more accurate than predicted for a nonpredatory rodent of its size.     

The organization of play fighting in the grasshopper mouse (Onychomys leucogaster): Mixing predatory and sociosexual targets and tactics

The body targets contacted, the type of contact made, and the patterns of defense and counterattack elicited by those attacks are examined in the play fighting of captive male and female pairs of grasshopper mice. The nape was the most frequently contacted body target, irrespective of the type of contact made, be it nosing, allogrooming, biting, or striking with a forepaw. The types of defense varied with both body area contacted and type of attack performed. Based on the topography and pattern of contact, it was concluded that grasshopper mice, as is the case for many other muroid rodents, primarily attack and defend targets otherwise contacted during precopulatory encounters. However, grasshopper mice, which are obligate carnivores, also attack and defend predatory targets, although less frequently than sociosexual targets. Surprisingly, predatory attacks were more likely to be counterattacked with predatory attacks, whereas sociosexual attacks were more likely to be counterattacked with sociosexual attacks. Conspecific aggression involves bites directed at the face, lower flanks, and dorsum. Neither the biting of these areas nor the tactics of attack and defense usually associated with such bites were observed during the juvenile interactions. There were no sex differences in either frequency or patterns of attack and defense in play fighting. The data presented for grasshopper mice shed light on the issue of mixing behavior patterns from multiple functional systems during play. Aggr. Behav. 26:319–334, 2000. © 2000 Wiley‐Liss, Inc.     

Prey-dependent effects of fluprazine hydrochloride on predatory aggression in northern grasshopper mice (Onychomys leucogaster) and rats (Rattus norvegicus)

Treatment with the phenylpiperazine DU 27716 (fluprazine hydrochloride) inhibited the predatory killing of albino mice by northern grasshopper mice (Onychomys leucogaster) and of frogs by rats. This treatment had no effect on cricket predation by grasshopper mice or worm predation by rats. The prey-specific effect of fluprazine did not seem to result from a decreased tendency to attack nor was its effect restricted to prey showing characteristic rodent defensive responses. Rather, the drug seemed to increase fearfulness when the prey exhibited vigorous defensive behavior. It is possible that increased fearfulness induced by treatment with this drug may also contribute to its antioffensive effect during conspecific encounters.     

Effects of preweaning predatory or consummatory experience and litter size on cricket predation in northern grasshopper mice (Onychomys leucogaster)

Preweaning exposure to cricket killing and consumption, but not consumption alone, facilitated postweaning cricket predation. This facilitatory effect did not result from kill-sharing by the parents or from food competition among the offspring. The results were strongly influenced by litter size. Small litters (N = 3–4) were strongly facilitated in all measures of predatory behavior when compared to litters of five to six mice. Since smaller litters of this species also show much higher levels of play behavior, it is suggested that play frequency may strongly facilitate later predatory behavior.     

Effects of some physiological and pharmacological manipulations on shock- facilitated mouse killing by onychomys leucogaster (Northern grasshopper mouse)

Onychomys leucogaster (northern grasshopper mice) were induced to kill mice with response-contingent shock, and the effects of several physiological, pharmacological, and endocrinological variables were assessed. Lesions of the septum facilitated mouse killing, while lesions of the amygdala abolished spontaneous mouse killing and delayed shock-facilitated killing. Chlorpromazine (2.5–5 mg/kg) and chlordiazepoxide (5–10 mg/kg) facilitated mouse killing on postdrug trials but did not affect killing when the animals were drugged. Adrenalectomy, castration, and castration adrenalectomy did not alter the frequency of kill nor were sex-related differences in killing noted. These results were compared to those found by others studying the effects of lesions and drugs on mouse killing by rats.     

Food deprivation: Effects on the predatory behavior of southern grasshopper mice (Onychomys torridus)

The southern grasshopper mouse (Onychomys torridus) is a predatory and aggressive rodent native to the semi-arid scrub deserts of the southwestern United States and northern Mexico. Its natural diet consists primarily of arthropods and small vertebrates. In this study, we have evaluated the effects of food deprivation on the predatory behavior of adult male and female grasshopper mice to crickets (Acheta domesticus) and laboratory mice (Mus musculus). Subjects that were food-deprived for 48 hours spent more time eating dead but not living crickets than did controls that were provided free access to laboratory chow. There were no sex differences in the predatory behavior of grasshopper mice to living or dead crickets. Food deprivation also influenced the predatory behavior of grasshopper mice toward laboratory mice. With laboratory chow available ad lib, 6 of 43 (14%) male and 22 of 45 (49%) female grasshopper mice killed and ate laboratory mice within 48 hours of pairing. When deprived of food for 48 hours, 16 of 36 (44%) males and 15 of 19 (79%) females that did not kill in the previous experiment killed and ate laboratory mice. We concluded that food deprivation and type of prey are two variables which influence the frequency and intensity of predatory behaviors of grasshopper mice.     

Hearing and vocalizations in the orange-fronted conure (Aratinga canicularis)

The auditory sensitivities of the orange-fronted conure (Aratinga canicularis) were examined in relation to the spectral characteristics of its vocalizations. Absolute thresholds, masked thresholds, frequency difference limens, and intensity difference limens for pure tones were obtained using psychoacoustic techniques. In general, hearing abilities are similar to those found in many avian auditory generalists. One exception is the unusually low critical ratio (masked threshold) between 2.0 and 4.0 kHz, similar to that previously found in the budgerigar (Melopsittacus undulatus). These auditory sensitivities were compared with average spectra for (a) contact calls and (b) a general sample of vocalizations recorded from wild birds. The spectral regions of both greatest vocal energy and best auditory sensitivity were between 2.0 and 5.0 kHz.     

Hearing in large mammals: sound-localization acuity in cattle (Bos taurus) and goats (Capra hircus).

Sound localization acuity of 3 cattle (Bos taurus) and 2 goats (Capra hircus) was determined for brief complex sounds in a two-choice procedure. Thresholds around the median sagittal plane averaged 30 degrees and 18 degrees, respectively. For comparison, thresholds were obtained in the same test apparatus for humans (0.8 degrees) and a dog (8 degrees). Although the relatively poor acuity of cattle and goats compared with most mammals comes as some surprise, given their large interaural distances and the large binaural locus cues available to them, it is not unexpected when other factors are considered. Like other poor localizers (both domesticated and nondomesticated), cattle and goats are prey species with their best vision directed throughout nearly the entire horizon. In contrast to mammals with very narrow foveal fields, they may not need very accurate locus information from their auditory systems to direct their gaze to a sound source.     

Washing, drying, and anointing in adult humans (Homo sapiens): commonalities with grooming sequences in rodents.

Very few behavioral patterns generalize across human and nonhuman species. We describe washing, drying, and anointing sequences in humans (Homo sapiens) that may have analogies with other species. The rank ordering of washing, drying, and anointing body parts was obtained over 3 successive days for 37 men and 60 women. Variation in rank ordering of body parts was nonrandom, and a cephalocaudal progression was evident for each behavior. Reliability of the behaviors as well as the correlations across rankings were highly significant, which indicates a generalized cephalocaudal progression for all 3 behaviors. Women's anointing was most variable, which suggests a more specific function. The cephalocaudal action pattern described for humans is similar to that for Mongolian gerbils and laboratory rats. Cross-species functions, such as these, may add to our understanding of common developmental and learning processes.     

Paternal care in the social and diurnal striped mouse (Rhabdomys pumilio): laboratory and field evidence

Paternal care is rare in mammals, occurring mainly in carnivores and neotropical primates, in which the difficulties of long generation time and large individuals lead to small sample sizes. Here, the authors show that paternal care can be easily studied in the four-striped mouse (Rhabdomys pumilio) because (a) captive males show all the patterns of parental care as do females, with the obvious exception of nursing; (b) in the field, wild males act amicably toward juveniles and retrieve pups experimentally presented to them; (c) the striped mouse facilitates experimental approaches in captivity because it has a short generation period and can be kept in large numbers; and (d) the striped mouse is diurnal, not only making observations in captivity easier but also enabling direct observations in the field.     

Watson's behaviorism: a comparison of the two editions (1925 and 1930)

J.B. Watson's Behaviorism, a complete presentation of the mature psychological points of view of its author, had 2 editions, in 1925 and 1930, which presented significant differences in their texts. Although Watson maximized such variations, to the point of considering the 2nd edition as nearly a brand-new book, both suppressions and additions reveal his feelings when presenting his ideas to a general audience. Such variations are here presented through an in-depth analysis.     

The easy-to-hard effect in human (Homo sapiens) and rat (Rattus norvegicus) auditory identification

The authors examined whether progressively training humans and rats to perform a difficult auditory identification task led to larger improvements than extensive training with highly similar sounds (the easy-to-hard effect). Practice improved humans' ability to distinguish sounds regardless of the training regimen. However, progressively trained subjects were more accurate and showed more generalization, despite significantly less training with the stimuli that were the most difficult to distinguish. Rats showed less capacity to improve with practice but still benefited from progressive training. These findings indicate that transitioning from an easier to a more difficult task during training can facilitate, and in some cases may be essential for, auditory perceptual learning. The results are not predicted by an explanation that assumes interaction of generalized excitation and inhibition but are consistent with a hierarchical account of perceptual learning in which the representational precision required to distinguish stimuli determines the mechanisms engaged during learning.     

Sociality and social learning in two species of corvids: the pinyon jay (Gymnorhinus cyanocephalus) and the Clark's nutcracker (Nucifraga columbiana)

The hypothesis that social learning is an adaptive specialization for social living predicts that social species should learn better socially than they do individually, but that nonsocial species should not exhibit a similar enhancement of performance under social learning conditions. The authors compared individual and social learning abilities in 2 corvid species: the highly social pinyon jay (Gymnorhinus cyanocephalus) and the less social Clark's nutcracker (Nucifraga columbiana). The birds were tested on 2 different tasks under individual and social learning conditions. Half learned a motor task individually and a discrimination task socially; the other half learned the motor task socially and the discrimination task individually. Pinyon jays learned faster socially than they did individually, but nutcrackers performed equally well under both learning conditions. Results support the hypothesis that social learning is an adaptive specialization for social living in pinyon jays.     

Interference in short-term memory: The magical number two (or three) in sentence processing

Many theories have been proposed to explain difficulty with center embedded constructions, most attributing the problem to some kind of limited-capacity short-term memory. However, these theories have developed for the most part independently of more traditional memory research, which has focused on uncovering general principles such as chunking and interference. This article attempts to gain some unification with this research by suggesting that an interesting range of core sentence processing phenomena can be explained as interference effects in a sharply limited syntactic working memory. These include difficult and acceptable embeddings, as well as certain limitations on ambiguity resolution, length effects in garden path structures, and the requirement for locality in syntactic structure. The theory takes the form of an architecture for parsing that can index no more than two constituents under the same syntactic relation. A limitation of two or three items shows up in a variety of other verbal short-term memory tasks as well.Preparation of this paper was supported by a grant from the James S. McDonnell Foundation to the Human Information Processing Group at Princeton University. Many thanks to Martin Chodorow, Terry Langendoen, Thad Polk, and an anonymous reviewer for helpful comments on the paper and research.     

Perceptual grouping in two visually reliant species: humans (Homo sapiens) and Australian sea lions (Neophoca cinerea).

Kurylo, van Nest, and Knepper (1997 Journal of Comparative Psychology 111 126-134) have recently shown that hooded rats are able to judge the global orientation of an array of elements if orientation is signalled by the perceptual-grouping principle of proximity, but not if it is signalled by element alignment. Using a procedure designed to overcome some potential problems with the experiment of Kurylo et al, we found the same distinction in the perceptual processing of Australian sea lions. The sea lions were able to judge the orientation of arrays containing strong proximity and similarity information, but performed at chance levels judging arrays in which element alignment signalled global orientation. Human subjects were able to judge all three pattern types quickly and accurately. This is strong evidence of a qualitative distinction in the way in which perceptual grouping operates in humans and the non-human species tested. Whether this distinction is a consequence of evolutionary or experiential factors is a question for future research, but the mere fact of a qualitative difference holds important implications for our understanding of perceptual grouping.     

Discriminability, loudness, and masking in the rat (Rattus norvegicus): a confirmation and extension

In Experiment 1, rats discriminated between two sound pressure levels (SPL) of a pure tone: standard (STD) SPLs of 84 and 74 dB and comparison (CO) SPLs 4, 14, and 24 dB below STD were tested in quiet and 60 dB noise at 4 and 12.5 kHz (24 conditions). The decibel difference between STD and CO accounted for only 43.52% of the variance in the signal detection measure of sensitivity, d', across conditions, whereas the loudness difference (LD = STD0.35 - CO0.35) accounted for 89.82% of the variance in d'. These results confirm and extend previous observations that: (a) equal decibel differences are not equally discriminable; (b) loudness for the rat increases as a power function of SPL with an exponent of 0.35: and (c) masked loudness is a linear function of loudness in quiet. In Experiment 2, the assumptions of normal distribution and equal variance implicit in the use of the d' measure were examined. Receiver operating characteristic curves that were well approximated by straight lines of unit slope in normal-normal coordinates were obtained and thereby validated the use of d' in Experiment 1.     

Lost in (cyber)space: finding two adolescent boys hiding from their own humanity

This article explores the intense psychological effects of compulsive Internet use, which has become increasingly common among adolescent boys and young men. Two cases are presented and discussed to illustrate some of the psychic distortions around thinking and feeling, as these occurred in the analysis of a mid‐adolescent boy and of another patient in later adolescence. A kind of narcissistic omnipotence grounded in magical thinking appeared to take root in their minds, and it led to an avoidant pattern in relationships because of such strong wishes for both distance and control. A short review of the conceptual origins of magical thinking underscores its continued relevance because so many now engage with the Internet. In addition, Anzieu's idea of the ‘skin ego’ is applied to the clinical case material to provide a theoretical framework for the developmental challenges that can appear in adolescent boys who seek to use the Internet as a form of psychic container. Emerging problems that immersion in the Internet might bring into our practices, for example the depleting effects of massive projective identification, are considered and discussed, along with the obvious ways in which using the Internet can be beneficial for connecting with others, for creating new platforms of expression, and for education.     

Cognitive parameters and morning and evening types: two decades of research (1990-2009)

An important area of study has examined cognitive aspects of morningness-eveningness orientation. Optimal times of efficiency in participants classified as Morning and Evening types are of great importance for understanding their cognitive abilities. The present review covers the last two decades (1990-2009), during which the important review by Tankova, Adan, and Buela-Casal appeared, and focuses particularly on attention, memory, and executive functions.