International Journal of Comparative Psychology

Several methodologies are available to evaluate how animals discriminate and perceive stimuli. These methodologies are described herein, and the kinds of questions that can be addressed with each technique, and its strengths and limitations,are addressed. De ction and discrimination studies are described that measure animal abilities, followed by classification and judgment studies that measure animal proclivities.  The choice of methodology is a consideration in experimental design, because the format of the question can direct, and sometimes define the answer. The experiments discussed emphasize that animals have multiple processing modes available to them that they use to classify stimuli. Detection and discrimination experiments may tap into one of those modes, while categorization and judgment experiments may address a different mode. A feature of these experiments is that they reduce the extent to which we view animal perception and cognition as distinct from human perception and cognition. Several methodologies are available to evaluate how animals discriminate and perceive stimuli. These methodologies are described herein, and the kinds of questions that can be addressed with each technique, and its strengths and limitations, are addressed. Detection and discrimination studies are described that measure animal abilities, followed by classification and judgment studies that measure animal proclivities. The choice of methodology is a consideration in experimental design, because the format of the q estion can direct, and sometimes define the answer. The experiments discussed emphasize that animals have multiple processing modes available to them that they use to classify stimuli. Detection and discrimination experiments may tap into one of those modes, while categorization and judgment experiments may address a different mode. A feature of these experiments is that they reduce the extent to which we view animal perception and cognition as distinct from human perception and cognition.

In the superior temporal sulcus (STS) of the macaque brain there are populations of cells which respond selectively to faces. Studies of these cells reveal that they are very sensitive to the direction of eye gaze and posture of the head of other subjects. It is argued that one function of the cells is to enable analysis of where other individuals are directing their attention. Given this selectivity for complex socially relevant stimuli it is surprising that the STS contains cells that respond to touch anywhere on the body or to any movement seen in the visual environment. We have investigated these tactile and motion sensitive cells to determine their behavioural significance. In the awake, behaving monkey we found that the critical dimension for polymodal coding is whether or not the sensations are expected. Tactile stimulation out of sight cannot be predicted and elicits neuronal responses. By contrast, when the monkey can see and, therefore, predict impending contact, or when the monkey touches a familiar surface in a predictable location, cell responses are reduced or abolished. In an analogous way some cells are unresponsive to the sight of the monkey's own limbs moving but respond to the sight of other moving stimuli. Since unpredictable sensations are often caused by other animals, the STS area appears well suited to defining sensory stimuli that are important in social or predator/prey interactions.

Budgerigars were trained with operant conditioning procedures to discriminate among sets of calls from several species in a Same-Different task. Response latencies from this task were analyzed in several ways including multidimensional scaling (MDS) and cluster analysis. The pattern of response latencies from budgerigars reared in a large group of conspecifics was compared to that of budgerigars reared in acoustic and social isolation. Results show that budgerigars with previous experience with species-specific vocalizations and isolate-reared birds who had never heard such sounds can both discriminate among the categories of species-specific vocal signals. But, results from MDS and cluster analysis also show that rearing budgerigars in isolation has subtle effects on the perception of these categories of vocal signals.

Blue

monkeys (Cercopithecus mitis) were trained to detect

acoustic signals

embedded in noise. Masked thresholds were determined for four hu

consonant-vowel speech

sounds (6a, pa, ga, and ka), and four blue monkey

(boom,

pyow, chirp, and trill). The ability of monkey listeners to hear these

was compared with humans. Results showed that monkey and human

was

very similar. The mean difference between species for these eight stimuli in

broad-band

noise environment was 2.3 dB. The signal-to-noise ratio for

ranged from

4.8 dB for the ka to -23.8 dB for the boom. The four monkey calls

audible

at a signal-to-noise level that was 8.1 dB less than that required for the

the speech sounds. However, most of this effect was due to the audibility of

boom.

With the boom excluded, the mean signal-to-noise ratio for detection of the re

7

sounds was -0.5 dB, and the mean difference in the audibility of

and

monkey sounds within this set was 2.6 dB. These results contrast

findings

which used simulated rain forest noise as the masking noise (Brown, 1986).

rain

forest noise, test signals were audible at signal-to-noise ratios approximately

dB

less than those reported here, and the observed difference in the

human and monkey utterances was larger. These findings

variations in

the amplitude and spectrum of the ambient noise may have

influence

on the

audibility of vocal signals in nature.

a strong

suggest that rather small

relative audibility

of

10

In

with previous

the speech

maining

the

detection

of

were

perception

the

hearing

signals in

noise

calls

man

complex

Human

infants' perception of tone sequences or melodies is reviewed

the context

of related work with human adults and nonhuman species. For the

part,

infants use an adult-like pitch processing strategy that is global and

rather

than the local pitch strategy that is characteristic of the nonhuman species stud

date. Thus they encode and retain the pitch configuration or contour of

with

little attention to the absolute pitches of individual notes. In the case

structured melodies,

specifically, melodies that are prototypical of Western music, in

encode

more precise relations, notably the intervals or exact pitch relations be

adjacent

notes. Finally, the functional significance of relational pitch

in

human infancy is

considered

processing

tween

fants

of well

a melody,

ied

to

relational

most

in

This paper discusses timing behavior as measured by Fixed (FI), Differential Reinforcement of Low rate (DRL) or Differential Reinforcement Response Duration (DRRD) performances, in humans and animals at different develop stages. Infants and rats display similar behavior patterns in FI and childhood on, humans develop species-specific behavior patterns in FI, which differ from those of animal species. However, DRL patterns do follow similar trends in animals and humans. These discrepancies and similarities may by the availability of cognitive and linguistic tools in humans, and the degree od schedule constraint on behavior. Motivation and reinforcer variables as well as to a cross-specific timing mechanism (such as scalar timing) are briefly commented upon. Available data tend to show that humans shift from contingency-shaped or "animal-like" behavior, in infancy, to rule-governed behavior. This transition is progressive and does not seem to erase forms of adaptation to temporal constraints that humans share with other species.