Auditory frequency discrimination in primates: Species differences (Cercopithecus, Macaca, Homo).

Auditory frequency difference limens (DLs) at 2 kHz were measured in Old World monkeys (Cercopithecus, Macaca) and humans using a go/no-go repeating standard procedure and positive reinforcement operant conditioning techniques. Quantitative and qualitative differences occurred between monkey and human sensitivity. Best DLs for monkeys were 20–60 Hz, and for humans they were 3–4 Hz. Monkey sensitivity decreased as sensation level increased from 30 to 70 dB, whereas human sensitivity increased. Sensitivity differences also occurred in the various monkey species. Cercopithecus monkeys were generally more sensitive to frequency decrements, whereas Japanese macaques were more sensitive to frequency increments, as were humans. Results are related to other comparative psychoacoustic data and primate vocal communication, including human speech. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Auditory intensity discrimination in blackbirds and pigeons.

Three male and 3 female redwing blackbirds, 2 male brown-headed cowbirds, and 2 male White Carneaux pigeons were trained with operant conditioning techniques to respond to small increases in the intensity of pulsed tone trains at 3 frequencies: .5, 1.0, and 2.0 kHz. All 3 species produced similar intensity difference limens (DLs) at the frequencies tested. Intensity DLs decreased as sensation level (intensity level above absolute threshold) increased at all 3 frequencies, with the slopes of these sensation level functions being greatest at 2.0 kHz. The median intensity DLs at 50 db sensation level were 3.3, 2.7, and 2.9 db at .5, 1.0, and 2.0 kHz, respectively, averaged over the 3 species. Some Ss were also required to detect decreases in intensity. They produced intensity DLs 2–3 times larger than the DLs obtained when these same Ss were required to detect increases in intensity. Avian intensity DLs generally appear to be 1–2 db higher than the DLs of those mammals that have been tested (rat, cat, monkey, humans). (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Discrimination of duration ratios by pigeons (Columba livia) and humans (Homo sapiens).

Humans were trained on 2 versions of a 2-alternative, forced-choice procedure. First, Ss judged which of 2 successive stimulus durations was longer. Second, Ss judged whether the ratio of the 2 durations was less or greater than a criterion ratio (e.g., 2:1). Accuracy was significantly lower for the task in which the judgment was made according to the ratio of the 2 durations. This result is different than that obtained by J. G. Fetterman et al (1989), who trained pigeons on a similar pair of tasks and found that pigeons' performance was comparable for the 2 discriminations. Comparisons of the pigeon and human data suggest that humans were more accurate than pigeons when the judgment involved which duration was longer, but that accuracy was comparable for the ratio-based task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perception of cliff swallow calls by birds (Hirundo pyrrhonota and Sturnus vulgaris) and humans (Homo sapiens).

Tested for species differences in the perception of the cliff swallow chick begging call. One cliff swallow, 3 European starling, and 3 human Ss were trained on go–no-go or repeating background tasks to discriminate between all possible stimulus pairs, measured by percentage of correct response and latency. Multidimensional scaling was used to convert the similarity measures into a 2-dimensional map for each S. Most of the maps were significantly correlated in Dimension 1 but not in Dimension 2. A cluster analysis separated bird and human maps. To identify the most important acoustic cues for each S, the coordinates of each dimension were regressed on acoustic variables measured from the stimuli. For all Ss, center frequency was Dimension 1. Different acoustic cues were associated with Dimension 2, with agreement only on bandwidth, by the cliff swallow and 1 starling. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Difference limens for formant patterns of vowel sounds

Studies of thresholds for discrimination of formant frequency variation in synthetic vowel sounds have been predominantly limited to variations in a single formant. Here, differences limens (DLs) are presented for multiformant variations expressed in measures of delta F and as distances in the auditory-perceptual space (APS) proposed by J. D. Miller [J. Acoust. Soc. Am. 85, 2114-2134 (1989)]. DLs for four subjects were estimated along 102 synthetic vowel continua representing five patterns of formant variation [(1) single variation in F1; (2) single variation in F2; (3) parallel simultaneous variation in F1 and F2; (4) opposing simultaneous variation in F1 and F2; and parallel simultaneous variation in F1, F2, and F3] and 17 within- or between-category vowel sounds. Minimal uncertainty methodology was employed utilizing an adaptive up-down procedure with a cued, two-interval forced-choice (2IFC) task. The results of this experiment reflect smaller DLs for both single- and multiple-formant changes than have been found in the past and also suggest that discrimination of parallel multiformant variation is significantly better than opposing multiformant or single-formant variation.     

Hearing in large mammals: Horses (Equus caballus) and cattle (Bos taurus).

Determined behavioral audiograms for 3 horses and 2 cows. Horses' hearing ranged from 55 Hz to 33.3 kHz, with a region of best sensitivity from 1 to 16 kHz. Cattle hearing ranged from 23 Hz to 35 kHz, with a well-defined point of best sensitivity at 8 kHz. Of the 2 species, cattle proved to have more acute hearing, with a lowest threshold of –21 db (re 20 μN/m–2) compared with the horses' lowest threshold of 7 db. Comparative analysis of the hearing abilities of these 2 species with those of other mammals provides further support for the relation between interaural distance and high-frequency hearing and between high- and low-frequency hearing. (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rhesus monkeys (macaca mulatta) immediately generalize the uncertain response.

Rhesus monkeys (Macaca mulatta) have learned, like humans, to use an uncertain response adaptively under test conditions that create uncertainty, suggesting a metacognitive process by which human and nonhuman primates may monitor their confidence and alter their behavior accordingly. In this study, 4 rhesus monkeys generalized their use of the uncertain response, without additional training, to 2 familiar tasks (2-choice discrimination learning and mirror-image matching to sample) that predictably and demonstrably produce uncertainty. The monkeys were significantly less likely to use the uncertain response on trials in which the answer might be known. These results indicate that monkeys, like humans, know when they do not know and that they can learn to use a symbol as a generalized means for indicating their uncertainty. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Delayed figure reconstruction by a chimpanzee (Pan troglodytes) and humans (Homo sapiens).

A chimpanzee (Pan troglodytes) was trained to construct a copy of 3-element compound figures from a set of 9 elements. Delay intervals between sample offset and element presentation varied. The chimpanzee maintained accuracy at about 80% correct for a delay of 32 s, which was slightly higher than the mean of 4 human (Homo sapiens) Ss. Excellent visual reproductive memory in the chimpanzee as compared with that in humans was demonstrated. However, the nature of the reproductive memory was different in the 2 species in that humans better constructed meaningful figures, which represented food items, than meaningless ones, whereas the chimpanzee constructed these 2 types of figures with the same accuracy. This outcome suggests that the reproductive memory for meaningful figures of the chimpanzee may have been processed separately from symbolic processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sequential Responding and Planning in Chimpanzees (Pan troglodytes) and Rhesus Macaques (Macaca mulatta).

Chimpanzees (Pan troglodytes) and rhesus macaques (Macaca mulatta) selected either Arabic numerals or colored squares on a computer monitor in a learned sequence. On shift trials, the locations of 2 stimuli were interchanged at some point. More errors were made when this interchange occurred for the next 2 stimuli to be selected than when the interchange was for stimuli later in the sequence. On mask trials, all remaining stimuli were occluded after the 1st selection. Performance exceeded chance levels for only 1 selection after these masks were applied. There was no difference in performance for either stimulus type (numerals or colors). The data indicated that the animals planned only the next selection during these computerized tasks as opposed to planning the entire response sequence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Posture and reaching in chimpanzees (Pan troglodytes) and orangutans (Pongo pygmaeus).

Hand preference in reaching was assessed under 2 postural adjustment conditions in 40 chimpanzees (Pan troglodytes) and 6 orangutans (Pongo pygmaeus). The postural conditions were quadrupedal and upright, during which reaching for food was scored on a minimum of 50 trials. Results indicated no population preference during quadrupedal reaching, but a right-hand population preference was found during upright reaching. There were no significant effects of age or sex on either the direction or strength of hand preference. Early rearing history affected the strength of hand preference but not direction. The results suggest that posture is an important factor in the assessment of hand preference in great apes and may have important evolutionary consequences. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Statistical classification of black-capped (Poecile atricapillus) and mountain chickadee (Poecile gambeli) call notes.

Both black-capped (Poecile atricapillus) and mountain chickadees (Poecile gambeli) produce a chick-a-dee call that consists of several distinct note types. In some regions, these 2 species live sympatrically, and it has been shown that 1 species will respond weakly to songs of the other. This suggests that chickadee song, and potentially other of their vocalizations, contains species-specific information. We tested the possibility that call notes were acoustically sufficient for species identification. Black-capped and mountain non-D notes were summarized as a set of 9 features and then analyzed by linear discriminant analysis. Linear discriminant analysis was able to use these notes to identify species with 100% accuracy. We repeated this approach, but with black-capped and mountain D notes that were summarized as a set of 4 features. Linear discriminant analysis was able to use these notes to identify species with 94% accuracy. This demonstrates that any of the note types in these chickadee calls possesses sufficient information for species classification. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A comparative study of geometric rule learning by nutcrackers (Nucifraga columbiana), pigeons (Columba livia) and jackdaws (Corvus monedula).

Three avian species, a seed-caching corvid (Clark's nutcrackers; Nucifraga columbiana), a non-seed-caching corvid (jackdaws; Corvus monedula), and a non-seed-caching columbid (pigeons; Columba livia), were tested for ability to learn to find a goal halfway between 2 landmarks when distance between the landmarks varied during training. All 3 species learned, but jackdaws took much longer than either pigeons or nutcrackers. The nutcrackers searched more accurately than either pigeons or jackdaws. Both nutcrackers and pigeons showed good transfer to novel landmark arrays in which interlandmark distances were novel, but inconclusive results were obtained from jackdaws. Species differences in this spatial task appear quantitative rather than qualitative and are associated with differences in natural history rather than phylogeny. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Avfail in color avoidance learning by starlings (Sturnus vulgaris) and red-winged blackbirds (Agelaius phoeniceus).

Certain unconditioned stimulus/stimuli (UCS) in flavor avoidance learning sometime become ineffective after pairings with relatively stronger UCS. This failure of avoidance learning (avfail) has been demonstrated only with rodents. The present investigations examined whether avfail might also occur with avian species, the food selection of which is guided primarily by visual cues. In Exp I, 20 male starlings were given pairings of 2 mg/kg methiocarb (a relatively weak UCS) and LiCl (a relatively strong UCS) in propylene glycol vehicle. In Exp II, 20 male red-winged blackbirds were given pairings of 2 or 4 mg/kg methiocarb (relatively weak and relatively strong UCS, respectively). Pairings were followed by a conditioning trial (UCS gavage in the presence of a color cue) and 2-choice tests. Conditioned avoidance was observed except (a) when methiocarb preceded LiCl and (b) when the low preceded the high methiocarb dose in preconditioning pairings. Exp III, with 20 Ss of each species, demonstrated that UCS habituation could not account for the results of Exps I and II. The data reflect avfail in the visual modality, and a biological implication of the results is that birds may not learn strong avoidance of aposematic prey containing varied levels of toxicant. (23 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Object permanence in orangutans (Pongo pygmaeus), chimpanzees (Pan troglodytes), and children (Homo sapiens).

Juvenile and adult orangutans (n?=?5; Pongo pygmaeus), chimpanzees (n?=?7; Pan troglodytes), and 19- and 26-month-old children (n?=?24; Homo sapiens) received visible and invisible displacements. Three containers were presented forming a straight line, and a small box was used to displace a reward under them. Subjects received 3 types of displacement: single (the box visited 1 container), double adjacent (the box visited 2 contiguous containers), and double nonadjacent (the box visited 2 noncontiguous containers). All species performed at comparable levels, solving all problems except the invisible nonadjacent displacements. Visible displacements were easier than invisible, and single were easier than double displacements. In a 2nd experiment, subjects saw the baiting of either 2 adjacent or 2 nonadjacent containers with no displacements. All species selected the empty container more often when the baited containers were nonadjacent than when they were adjacent. It is hypothesized that a response bias and inhibition problem were responsible for the poor performance in nonadjacent displacements. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of noise on pure-tone thresholds in blackbirds (Agelaius phoeniceus and Molothrus ater) and pigeons (Columba livia).

Blackbirds and pigeons were trained to detect tones in quiet and in broadband noise by using positive-reinforcement techniques. In Experiment 1, thresholds in noise were obtained in blackbirds as a function of both tone frequency and noise intensity for a pulsed noise masker (noise gated on and off with tone). For blackbirds, critical ratios (the ratio of the power of the just-detectable tone in noise to the power of the noise masker) obtained in pulsed noise showed no consistent relation to tone frequency. For pigeons, on the other hand, critical ratios obtained in continuous noise increased by about 3 dB/octave across their range of hearing, being similar to known critical ratio functions for cats and humans. In Experiment 2, critical ratios in blackbirds obtained with both continuous noise and pulsed noise were compared. Blackbird critical ratios were more stable in continuous noise and averaged 4 dB lower than critical ratios in pulsed noise. The blackbird critical ratio function obtained with continuous noise was similar to the known critical ratio function of another avian species, the parakeet. Thus, small birds appear to have atypical critical ratio functions, compared with pigeons and other vertebrates. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The dolphin's (Tursiops truncatus) understanding of human gazing and pointing: Knowing what and where.

The authors tested whether the understanding by dolphins (Tursiops truncatus) of human pointing and head-gazing cues extends to knowing the identity of an indicated object as well as its location. In Experiment 1, the dolphins Phoenix and Akeakamai processed the identity of a cued object (of 2 that were present), as shown by their success in selecting a matching object from among 2 alternatives remotely located. Phoenix was errorless on first trials in this task. In Experiment 2, Phoenix reliably responded to a cued object in alternate ways, either by matching it or by acting directly on it, with each type of response signaled by a distinct gestural command given after the indicative cue. She never confused matching and acting. In Experiment 3, Akeakamai was able to process the geometry of pointing cues (but not head-gazing cues), as revealed by her errorless responses to either a proximal or distal object simultaneously present, when each object was indicated only by the angle at which the informant pointed. The overall results establish that these dolphins could identify, through indicative cues alone, what a human is attending to as well as where. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Infants' detection of increments in low- and high-frequency noise

A visually reinforced operant paradigm was employed to examine the relationship between the difference limen (DL) for intensity and level of the standard during infancy. In Experiment 1, 7-month-old infants and adults detected increments in continuous noise presented via headphones at each of four levels ranging from 28 to 58 dB SPL. Noise stimuli were 2-octave bands centered at either 400 or 4000 Hz, and increments were 10 and 100 msec in duration. Infants' DLs were significantly larger than those of adult subjects and significantly larger for low- than for high-frequency stimuli. For the high-frequency noise band, infants' DLs were generally consistent with Weber's law, remaining essentially constant for standards higher than 28 dB SPL (3 dB SL) for 100-msec increments and 38 dB SPL (13 dB SL) for 10-msec increments. For low-frequency noise, infants' absolute thresholds were exceptionally high, and sensation levels of the standards were too low to adequately describe the relationship. In Experiment 2, 7-month-old infants detected 10- and 100-msec increments in 400-Hz noise stimuli presented in sound field. Infants' low-frequency DLs were large at low intensities and decreased with increases in level of the standard up to at least 30 dB SL. For both low- and high-frequency noise, the difference between DLs for 10- and 100-msec increments tended to be large at low levels of the standard and to decrease at higher levels. These results suggest that the relationship between the DL and level of the standard varies with both stimulus frequency and duration during infancy. However, stimulus-dependent immaturities in increment detection may be most evident at levels within approximately 30 dB of absolute threshold.     

Do Chimpanzees (Pan troglodytes) and 2-Year-Old Children (Homo sapiens) Understand Double Invisible Displacement?

Chimpanzees (Pan troglodytes) and young children (Homo sapiens) have difficulty with double invisible displacements in which an object is hidden in two nonadjacent boxes in a linear array. Experiment 1 eliminated the possibility that chimpanzees' previous poor performance was due to the hiding direction of the displacement device. As in Call (2001), subjects failed double nonadjacent displacements, showing a tendency to select adjacent boxes. In Experiments 2 and 3, chimpanzees and 24-month-old children were tested on a new adaptation of the task in which four hiding boxes were presented in a diamond-shaped array on a vertical plane. Both species performed above chance on double invisible displacements using this format, suggesting that previous poor performance was due to a response bias or inhibition problem rather than a fundamental limitation in representational capacity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Imitative learning of artificial fruit processing in children (Homo sapiens) and chimpanzees (Pan troglodytes).

Observational learning in chimpanzees and young children was investigated using an artificial fruit designed as an analog of natural foraging problems faced by primates. Each of 3 principal components could be removed in 2 alternative ways, demonstration of only one of which was watched by each subject. This permitted subsequent imitation by subjects to be distinguished from stimulus enhancement. Children aged 2–4 years evidenced imitation for 2 components, but also achieved demonstrated outcomes through their own techniques. Chimpanzees relied even more on their own techniques, but they did imitate elements of 1 component of the task. To our knowledge, this is the first experimental evidence of chimpanzee imitation in a functional task designed to simulate foraging behavior hypothesized to be transmitted culturally in the wild. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Auditory sensitivity of the redwing Blackbird (Agelaius phoeniceus) and brown-headed cowbird (Molothrus ater)..

Used 3 behavioral procedures to measure the auditory sensitivity of 10 redwing blackbirds and 6 brown-headed cowbirds. In the 1st procedure, a go-left/go-right task, an S initiated a trial by pecking a center key; a tone was presented with 50% probability on each trial. An S was rewarded with grain for pecking a right or left key, depending on whether a tone was present or not. In the 2nd, a go/no-go procedure, an S pecked the center key continuously until a 2-sec tone sounded; reinforcement then occurred if the S pecked the right-side key during the tone. In the 3rd, a modified go/no-go procedure, clearly audible tones were inserted into the regular go/no-go procedure whenever near-threshold tones were missed. All procedures produced similar thresholds for both redwings and cowbirds; hearing encompassed the range from 125 to 10 kHz, with lowest thresholds of 4–20 db sound-pressure level in the 2–4 kHz range. Two pigeon control Ss gave stable thresholds only under the modified go/no-go procedure. (23 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)