Auditory discrimination of tone-pulse onsets

Two experiments are reported in which difference limens (DLs) were measured for onset times of a 1000-Hz tone pulse. An adaptive two-alternative forced-choice procedure and (mostly) well-trained subjects were used. In the first experiment, DLs were measured for the rise time of linear onset ramps at rise-time values between 10 and 60 msec. The DLs follow Weber's law up to a rise time of about 50 msec, and do not support the notion that rise times are perceived in a categorical manner. In the second experiment, DLs were obtained for linear, exponential, and raised-cosine onset envelopes at rise-time values between 10 and 40 msec. When energy differences in the critical band around 1000 Hz are computed for just-discriminable onsets, values between 0.7 dB (10-msec rise time) and 0.3 dB (40-sec rise time) are found. These equivalent intensity DLs show the same "near miss to Weber's law" behavior as do intensity DLs for pure tones.     

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 Ex-periment 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.     

Difference threshold for intensity of tactile stimuli

The difference threshold (DL) for brief tactile stimuli (taps) and vibrotactile stimuli was determined using a 2IFC procedure. The measurements were made at several intensities both in quiet and in the presence of a background vibration. The results show that in the absence of background vibration the DLs for higher intensity stimuli are similar for both taps and vibration, whereas at lower intensities the DL is larger for taps. In the presence of background vibration the DL for vibratory stimuli is elevated to a much greater extent than it is for tap stimuli. The DL is affected by both the intensity of the signal and the intensity of the background vibration.     

The measurement of differential thresholds for lifted weights by microcomputer-controlled apparatus

The measurement of differential thresholds (DLs) for lifted weights normally involves lengthy test sessions. This is due partly to the statistical techniques for measuring the threshold and partly to the methods adopted to present the stimuli. Attempts to speed up test procedures tend to produce unreliable DL estimates, or to measure the sense of force or effort rather than weight perception. To facilitate the measurement of DLs for lifted weights, an Apple microcomputer was programmed to generate Wetherill tracking procedures and was interfaced with two stimulus bearing turntables. Various lifting methods are easily implemented, and DLs are reliably and quickly measured. The adaptation of the apparatus for general use in investigating the haptic sense modality is discussed.     

Size and reliability of frequency-difference thresholds determined with operant tracking procedure

Auditory frequency discrimination thresholds have been determined by a “tracking procedure” at five frequencies and two intensity levels for a group of four cats. Intra-animal thresholds were found to be quite stable, and there was good inter-animal agreement among three of the four cats. Although quite stable, the tracking thresholds were larger than those which had been obtained using an avoidance procedure. However, because of the several differences between the tracking procedure and avoidance conditioning procedure, no conclusions can be drawn concerning the efficacy of the different types of reinforcement in determining the ultimate limit of the animals' discrimination ability.     

Visual evoked potential augmenting/reducing slopes in cats—2. Correlations with behavior

Relationships were studied in cats between the augmenting/reducing slopes of visual evoked potentials (VEP) and three types of behavioral responses: learning and performance measures in (1) fixed interval (FI), and (2) differential reinforcement of low rate of response (DRL) bar pressing tasks for food reward, and (3) the effect of noise stress or increasing task difficulty on performance of an FI, DRL or 2 bar discrimination task. The most reliable slope measure (N1 at a medium intensity range) was found to correlate most highly with inhibitory behaviors such that reducers were most successful in controlling bar pressing behavior during an inhibitory DRL task or when stress was introduced. At a higher range of flash intensity slopes tended to be more negative, and the P1 - N1 slopes although more variable correlated most consistently with general temperament. Augmenters at a high intensity range were more active and explaratory, and learmed to bar press more quickly and efficiently.     

Conditioned leg movement in the cat with massed trials,trace conditioning,and weak US intensity

Six male cats served as subjects in a classical conditioning experiment designed to assess the development of an overt conditioned response with experimental parameters that had been demonstrated to produce conditioning of neuro-electrical activity in immobilized cats. The subjects were physically restrained by means of an adjustable full-body cast during the experimental sessions which consisted of 75 habituation trials (light flash alone) followed by 225 trials with light and shock paired in a trace conditioning manner, and 75 additional extinction trials (light alone). The subjects were divided into two groups, and three different experimental sessions were given to each on three consecutive days. Group I received low US intensity (18 v) conditioning on the first day, high US (45–85 v) conditioning on Day 2 and pseudoconditioning on Day 3. Group II received the same sessions, but in a pseudoconditioning —high US—low US order. The results indicated that a conditioned leg movement was produced when the CS was paired in a trace conditioning fashion with either the high or low intensity shock US. The development of the conditioned leg movement across trials was found to be very similar to that of the conditioned neural activity in a previous study using comparable stimuli and procedures.     

Duration of cats' (Felis catus) working memory for disappearing objects

This study explored the duration of cats' working memory for hidden objects. Twenty-four cats were equally divided into four groups, which differed according to the type of visual cues displayed on and/or around the hiding boxes. During eight sessions, the four groups of cats were trained to locate a desirable object hidden behind one of the four boxes placed in front of them. Then, the cats were tested with retention intervals of 0, 10, 30 and 60 s. Results revealed no significant differences between the groups during training or testing. In testing, the cats' accuracy to locate the hidden object rapidly declined between 0 and 30 s but remained higher than chance with delays of up to 60 s. The analysis of errors also indicated that the cats searched as a function of the proximity of the target box and were not subjected to intertrial proactive interference. This experiment reveals that the duration of cats' working memory for disappearing objects is limited and the visual cues displayed on and/or around the boxes do not help the cats to memorize a hiding position. In discussion, we explore why the duration of cats' working memory for disappearing objects rapidly declined and compare these finding with those from domestic dogs. The irrelevance of visual cues displayed on and around the hiding boxes on cats' retention capacity is also discussed.     

Object permanence in cats (Felis catus): an ecological approach to the study of invisible displacements.

A single invisible displacement object permanence task was administered to 19 cats (Felis catus). In this task, cats watched a target object from behind a transparent panel. However, cats had to walk around an opaque panel to reach the object. While cats were behind the opaque panel, the object was hidden behind one of two screens. As cats did not perceive the disappearance of the object behind the target screen, the object was invisibly hidden. Results showed that cats solved this task with great flexibility, which markedly contrasts with what has been observed in previous research. The discussion emphasizes the difference between the typical Piagetian task in which the information necessary to succeed must be dealt with in retrospective way, whereas in our task cats had to anticipate a new position of the object. The ecological relevance of this new task is also discussed.     

There’s no ball without noise: cats’ prediction of an object from noise

We used an expectancy violation procedure to ask whether cats could use a causal rule to infer the presence of an unseen object on hearing the noise it made inside a container and predict its appearance when the container was turned over. We presented cats with either an object dropping out of an opaque container or no object dropping out (turning-over phase) after producing either a rattling sound by shaking the container with the object inside, or no sound (shaking phase). The cats were then allowed to freely explore the experimental environment (exploration phase). The relation between the sound and the object matched with physical laws in half of the trials (congruent condition) and mismatched in the other half (incongruent condition). Inferring the presence of an unseen object from the noise was predicted to result in longer looking time in the incongruent condition. The prediction was supported by the cats’ behavior during the turning-over phase. The results suggest that cats used a causal-logical understanding of auditory stimuli to predict the appearance of invisible objects. The ecology of cats’ natural hunting style may favor the ability for inference on the basis of sounds.     

The ontogenesis of lateralized behavior in the domestic cat, Felis silvestris catus

For the first time, the development of paw preferences in the domestic cat, Felis silvestris catus, is explored. Twelve cats were tested at ages 12 weeks, 6 months, and 1 year on a challenge requiring them to use one of their paws to retrieve food. To control for repeated testing of the same cats at different ages, the subjects' paw preferences were compared with those of cats tested just once, at 6 months (n = 11) or 1 year (n = 14) of age. Analysis revealed a significant effect of age on the distribution of cats' paw preferences. Cats were significantly more likely to be ambilateral than paw preferent at 12 weeks and at 6 months but more likely to display a lateral bias in paw use at 1 year. There was a significant positive correlation between cats' paw preferences at 6 months and at 1 year. Lateralized behavior was strongly sex related. Females had a greater preference for using their right paw; males were significantly more inclined to adopt their left. Analysis revealed no significant difference in the direction or strength of paw preferences of cats tested longitudinally or cross-sectionally at 6 months or 1 year of age. Findings indicate that cats develop paw preferences by 1 year and hint at a relative stability in preferred paw use over time. The strong sex effect observed strengthens the case for the influence of a biological mechanism in the emergence of motor asymmetry in cats.     

Auditory masking-level differences in the cat.

Four cats were trained to avoid shock by responding to the intermittent occurrence of 1-kHz tone pulses at one ear, while a continual train of noise pulses was simultaneously presented either to the signal ear alone or to both ears. Using the masked threshold levels determined with monaural noise as a reference, the amount of unmasking produced by the addition of noise to the nonsignal ear was measured. Significantly lower tonal detection thresholds were observed when noise equal in intensity to that at the signal ear was added to the nonsignal ear. Additional unmasking occurred when the intensity of the noise at the latter ear was raised to a level 10 db. higher than that at the signal ear.     

A comparison of method-of-adjustment and forced-choice procedures in frequency discrimination

Reported estimates of the frequency difference limen (DL) for tones show considerable variability. To determine the extent that the differences are dependent on psychophysical method, three estimates of the DL at 1,000 Hz were obtained from the same subjects for each of three psychophysical procedures. The three estimates were: (1) the standard deviation of final settings in a methbd of adjustment, (2) the average of several reversals in an adaptive two-interval forced-choice procedure, and (3) the 76%-correct point in a two-interval forced-choice procedure using constant stimuli. The two forced-choice procedures yielded very similar DLs. The adjustment procedure yielded significantly smaller estimates. Possible reasons for the different values produced by adjustment procedures and the nature of the underlying decision process are discussed.     

Vocal recognition of owners by domestic cats (Felis catus)

Domestic cats have had a 10,000-year history of cohabitation with humans and seem to have the ability to communicate with humans. However, this has not been widely examined. We studied 20 domestic cats to investigate whether they could recognize their owners by using voices that called out the subjects’ names, with a habituation–dishabituation method. While the owner was out of the cat’s sight, we played three different strangers’ voices serially, followed by the owner’s voice. We recorded the cat’s reactions to the voices and categorized them into six behavioral categories. In addition, ten naive raters rated the cats’ response magnitudes. The cats responded to human voices not by communicative behavior (vocalization and tail movement), but by orienting behavior (ear movement and head movement). This tendency did not change even when they were called by their owners. Of the 20 cats, 15 demonstrated a lower response magnitude to the third voice than to the first voice. These habituated cats showed a significant rebound in response to the subsequent presentation of their owners’ voices. This result indicates that cats are able to use vocal cues alone to distinguish between humans.     

Normal and abnormal visual development in kittens: insights into the mechanisms that underlie visual perceptual development in humans

For many years the mechanisms that underlie normal and abnormal development of visual perception in human infants have been explored in anatomical and physiological studies on two species of frontal-eyed mammals, namely, cats and, to a lesser extent, monkeys. The unstated assumption underlying the investigations on cats is that despite substantial differences in the organization of the visual pathways of cats and humans, as well as quantitative differences in their perceptual abilities, principles of development established in the former also apply to humans. This review examines the extent to which this assumption may be valid. Following a review of certain anatomical peculiarities of the cat visual system, several of the differences as well as the parallels between the perceptual abilities of cats and humans are summarized. The latter similarities, as well as the larger number of parallels between the two species that can be drawn during development, attest to the validity of the choice of the cat for study of the mechanisms that underlie human visual development.     

Frequency discrimination near masked threshold

Frequency DLs (Δf) at 1000 Hz were obtained in quiet and under masking conditions similar to those used in pitch-shift experiments, narrow-band noise at levels of 60, 80, and 100 dB SPL and tones at 15 dB SL or less. The Δfs were obtained by means of a tracking task in which the S controlled the input voltage to a frequency modulator. Characteristic improvement was seen when Δf was plotted as a function of sensation level. However, noise level itself was a significant factor, with more intense noise resulting in larger Δfs for tones of equal sensation level re masked threshold. This departure from previous findings is attributed to the signal and noise levels used, although the possibility exists that it is due to the use of modulated tones.     

Blocking of inhibitory conditioning within a serial conditioned stimulus-conditioned inhibitor compound: Maintenance of acquired behavior without an unconditioned stimulus

Well-trained classically conditioned stimuli, presented unreinforced, were protected from extinction when they were followed by a signal of the omission of the reinforcer (conditioned inhibitor Konorskian type) in eight cats. An aversive classical conditioning paradigm with shock as the reinforcer was used. Of several behavioral (leg flexion, vocalization) and organismic arousal (heart rate, respiration rate, respiration amplitude) measures of conditioned responses, the respiration amplitude changes were found to be most informative for the continuous assessment of elicited arousal of low and medium intensity. In all subjects conditioned stimuli presented during extinction in serial compound with the conditioned inhibitor elicited larger responses than did conditioned stimuli presented alone during extinction. The mechanism of protection from extinction in a paradigm in which the elicitor of learned behavior occurs prior to the conditioned inhibitor provides the organism with the mechanism for the maintenance of learned behavior in the absence of a reinforcer.     

Food-searching behavior of cats in a multiple-choice elimination problem

Twelve cats were individually exposed to a four-point elimination problem for 50 consecutive days. The problem for the animals consisted of choosing a series of different points where they found, and were allowed to eat, a piece of meat, without returning to any previously visited point. The order of elimination was not controlled in any way by the experimenter. Results indicated that cats were able to solve this problem. All subjects showed a strong tendency to make successive runs toward points situated as far apart as possible. Moreover, a relation was shown between performance and the tendency to follow this high divergence principle. This result is discussed in terms of subjects' ability to process information about the spatial characteristics of the experimental situation. This ability might in fact be related to the behavioral plasticity of animals in spatial problems according to the difficulty of the task.     

The effects of atropine on viscerovisceral reactions and the electrocardiogram of the cat

In 12 chronic cats the effects of mechanical stimulation (distention) of the gallbladder on heart rate, respiratory movements and bioelectrical activity of the cerebral cortex were studied under normal conditions and after intraperitoneal administration of atropine. In the control group without atropine a decrease or an increase of heart rate and of respiratory movements occurred, depending on stimulation intensity. These changes were independent of an activated or inactivated EKG. Behavioral arousal was not seen in every cat. After administration of atropine in doses from 0.2 to 2.0 mg per kg body weight, the changes in heart rate, respiration and EKG were suppressed or completely disappeared.