AUDITORY SUCCESSIVE CONDITIONAL DISCRIMINATION AND AUDITORY STIMULUS EQUIVALENCE CLASSES

This paper describes an experimental demonstration of stimulus equivalence classes consisting entirely of auditory stimuli. Stimuli were digitized arbitrary syllables (e.g., “cug,” “vek”) presented via microcomputer. Training and testing were conducted with a two-choice auditory successive conditional discrimination procedure. On each trial, auditory samples and comparisons were presented successively. As each comparison was presented, a response location (a rectangle) appeared on the computer screen. After all stimuli for a trial were presented, subjects selected one of the response locations. Six subjects acquired the conditional discrimination baseline, 4 subjects demonstrated the formation of three-member auditory equivalence classes resulting from sample-S+ relations, and 1 subject demonstrated equivalence classes resulting from sample-S— relations. Four subjects received additional training and subsequently demonstrated expansion of the three-member classes to four members each.     

Investigations of perception and imagery using CAEs: The role of experimental design and psychophysical method

Orientation-contingent color aftereffects (CAEs) were measured using 174 observers ran-domly allocated to one of eight experimental conditions formed by the factorial combination of three two-level factors. These were experimental design (pretest and posttest measures taken vs. posttest measures taken alone), psychophysical method (forced-choice vs. magnitude estimation), and inspection procedure (inspection of real contours vs. inspection of imagined contours). In addition to color responses, written introspective reports of the strategies used in providing color responses were obtained. As a basis for the rejection of observers using inappropriate strategies, reported strategies were coded as appropriate or inappropriate. An analysis of the color reports of all observers was performed, as well as two analyses of the color reports of only those observers identified as using appropriate response strategies. In all cases, the results showed that CAEs were reported after inspection of real contours irrespective of the experimental design or psychophysical method used. There were no significant CAEs reported in any conditions that involved the imagination of contours. A separate analysis of the relationship between observers’ response strategies, the coding of these strategies, and observers’ actual color reports revealed some problems concerning the use of such introspective techniques. The implications of these findings are discussed in terms of theoretical assumptions about the nature of imagery and perception.     

Taï chimpanzees use botanical skills to discover fruit: what we can learn from their mistakes

Fruit foragers are known to use spatial memory to relocate fruit, yet it is unclear how they manage to find fruit in the first place. In this study, we investigated whether chimpanzees (Pan troglodytes verus) in the Taï National Park make use of fruiting synchrony, the simultaneous emergence of fruit in trees of the same species, which can be used together with sensory cues, such as sight and smell, to discover fruit. We conducted observations of inspections, the visual checking of fruit availability in trees, and focused our analyses on inspections of empty trees, so to say “mistakes”. Learning from their “mistakes”, we found that chimpanzees had expectations of finding fruit days before feeding on it and significantly increased inspection activity after tasting the first fruit. Neither the duration of feeding nor density of fruit-bearing trees in the territory could account for the variation in inspection activity, which suggests chimpanzees did not simply develop a taste for specific fruit on which they had fed frequently. Instead, inspection activity was predicted by a botanical feature—the level of synchrony in fruit production of encountered trees. We conclude that chimpanzees make use of the synchronous emergence of rainforest fruits during daily foraging and base their expectations of finding fruit on a combination of botanical knowledge founded on the success rates of fruit discovery, and a categorization of fruit species. Our results provide new insights into the variety of food-finding strategies employed by primates and the adaptive value of categorization capacities.     

Two kinds of bias in visual comparison illustrate the role of location and holistic/analytic processing differences

A number of studies have shown that two stimuli appearing successively at the same spatial location are more likely to be perceived as the same, even though location is irrelevant to the task. This bias to respond “same” when stimuli are at the same location is termed spatial congruency bias. The experiments reported here demonstrate that the spatial congruency bias extends to letter strings: Participants tend to respond “same” when comparing two strings appearing successively at the same location. This bias may arise because successive stimuli at the same location are more likely to be perceived as a single object. Bias is also affected by the nature of the comparison task. We show that if letters must be compared individually (analytical comparison), there is a bias to respond “different,” but if letter strings are compared as unified wholes (holistic comparison), there is no bias or a bias to respond “same.” This analytical bias is apparently separate from the spatial congruency bias. It appears whether the task requires localization of differences between strings, or counting the number of differences, or ignoring differences in some parts of the stimuli while attending to others. All of these analytical comparison tasks require that letters be selected individually, and the analytical bias may reflect difficulty in preventing interference from neighboring letters in this selection process. Each type of bias reflects a different aspect of visual processing, and both can be measured to probe how processing changes across different tasks.     

A pitfall for the expectancy theory of human eyelid conditioning

Two simple eyeblink conditioning experiments with random intermittent reinforcement schedules were performed. In Experiment 1, subjects had to rate their expectancy for an unconditioned stimulus (US) on a seven-level scale prior to each trial. As anticipated, expectancy for US increased with a successive conditioned stimulus (CS) alone, and decreased with successive CS-US pairings. However, Experiments 1 and 2 showed that the frequency of eyeblink conditioned responses (CRs) evolved in a direction opposite to that of expectancy changes: CRs increased, whereas expectancy for US decreased, and vice versa. The possible effect of sensitization on eyeblink response was ruled out by the lack of a run effect in an unpaired control group in Experiment 2. These results tend to disconfirm the expectancy theory of conditioning. Although they were explicitly predicted by the conventional “strength” theory of conditioning, an alternative interpretation is proposed within a cognitive framework.     

Binocular summation in the perception of form at brief durations

Visual form identification at brief durations was studied under: (a) monocular presentation; (b) dichopic presentation where the same form was presented successively on noncorresponding areas; and (c) dichopic presentation where the same form was presented on corresponding areas simultaneously and successively. Form identification for noncorresponding area dichopic presentation was at the level to be expected from 2 independent chances to perceive. Both simultaneous and successive dichopic presentation on corresponding areas gave identification accuracy significantly above the level predicted by the assumption of independence. However, the binocular summation was not complete. When the same amount of energy entering the visual system in a binocular presentation was given in a monocular stimulation, the latter condition gave significantly better identification.     

Binocular summation in the perception of form at brief durations

Visual form identification at brief durations was studied under: (a) monocular presentation; (b) dichopic presentation where the same form was presented successively on noncorresponding areas; and (c) dichopic presentation where the same form was presented on corresponding areas simultaneously and successively. Form identification for noncorresponding area dichopic presentation was at the level to be expected from 2independent chances to perceive. Both simultaneous and successive dichopic presentation on corresponding areas gave identification accuracy significantly above the level predicted by the assumption of independence. However, the binocular summation was not complete. When the same amount of energy entering the visual system in a binocular presentation was given in a monocular stimulation, the latter condition gave significantly better identification.     

Apport démographique de l’immigration internationale dans la région Métropolitaine de recensement (RMR) de Montréal, 1976–1996

This study assesses the total net demographic contribution of international immigrants in the census metropolitan area (CMA) of Montreal in 1996. Most work on this topic uses the “place of birth” criterion implied by the concept of a “native born” population. However, this limits the “immigrant population”, by inappropriately assigning births to immigrants to the non-immigrant or “native born” sub-population. This has a direct effect on the levels of observed indicators of both groups, such as the proportion of the immigrant population, the mean age, the median age etc. In addition to the total number of surviving migrants (direct contribution), the estimate here also includes children born to the immigrants during the period (1976–1996) and surviving in Montreal at the end of the period (indirect contribution). Montreal’s total population in 1996 can therefore be broken down into the “extended immigrant population” (EIP) and the “restricted native population” (RNP). One of the main consequences of this new approach is a marked change in the age structure for each restructured sub-group. For instance, once the births to immigrants during the period under study are included in the EIP instead of the “native population”, the median age of immigrants drops from 43.9 years to 38.2 years, a reduction of almost six years, bringing it much closer to that age in the population as a whole (36.2 years).     

Perceptual hysteresis in the judgment of auditory pitch shift

Perceptual hysteresis can be defined as the enduring influence of the recent past on current perception. Here, hysteresis was investigated in a basic auditory task: pitch comparisons between successive tones. On each trial, listeners were presented with pairs of tones and asked to report the direction of subjective pitch shift, as either “up” or “down.” All tones were complexes known as Shepard tones (Shepard, 1964), which comprise several frequency components at octave multiples of a base frequency. The results showed that perceptual judgments were determined both by stimulus-related factors (the interval ratio between the base frequencies within a pair) and by recent context (the intervals in the two previous trials). When tones were presented in ordered sequences, for which the frequency interval between tones was varied in a progressive manner, strong hysteresis was found. In particular, ambiguous stimuli that led to equal probabilities of “up” and “down” responses within a randomized context were almost fully determined within an ordered context. Moreover, hysteresis did not act on the direction of the reported pitch shift, but rather on the perceptual representation of each tone. Thus, hysteresis could be observed within sequences in which listeners varied between “up” and “down” responses, enabling us to largely rule out confounds related to response bias. The strength of the perceptual hysteresis observed suggests that the ongoing context may have a substantial influence on fundamental aspects of auditory perception, such as how we perceive the changes in pitch between successive sounds.     

The effects of ITI fillers in autoshaping

The present experiments used pigeons in an autoshaping procedure to examine the effects of a nonreinforced, nontarget stimulus presented during the intertrial interval on responding to a target CS. Experiments 1 and 2 found that a filler stimulus presented during a substantial portion of the ITI retarded responding to the target CS relative to a group not exposed to the filler. This group difference in performance was subsequently abolished by continued training and omitting the filler in the former group (Experiment 1) or adding a filler for the latter group (Experiment 2). Experiment 3 found that when the “filler” occupied most of the interreinforcement interval, CS-US pairings embedded within the “filler” stimulus yielded superior autoshaping relative to a group that received CS-US pairings embedded in static apparatus cues in the absence of the filler. The results are discussed with reference to the ways that a nontarget stimulus during the ITI can influence contextual modulation of responding to a discrete CS and the necessity for comparator theories to incorporate a “local context” view of cycle time to explain the present findings.     

There's more to emotion than meets the eye: A processing bias for neutral content in the domain of emotional prosody

Research on emotion processing in the visual modality suggests a processing advantage for emotionally salient stimuli, even at early sensory stages; however, results concerning the auditory correlates are inconsistent. We present two experiments that employed a gating paradigm to investigate emotional prosody. In Experiment 1, participants heard successively building segments of Jabberwocky “sentences” spoken with happy, angry, or neutral intonation. After each segment, participants indicated the emotion conveyed and rated their confidence in their decision. Participants in Experiment 2 also heard Jabberwocky “sentences” in successive increments, with half discriminating happy from neutral prosody, and half discriminating angry from neutral prosody. Participants in both experiments identified neutral prosody more rapidly and accurately than happy or angry prosody. Confidence ratings were greater for neutral sentences, and error patterns also indicated a bias for recognising neutral prosody. Taken together, results suggest that enhanced processing of emotional content may be constrained by stimulus modality.     

Nonverbal discrimination of more and fewer elements by children

Fifty-six prekindergarten and 174 kindergarten children learned to choose either the card with more or the card with fewer elements in simultaneous discrimination problems. Learning was faster when the card with more elements was positive, particularly when a zero-element card was involved. This difference appeared to be attributable in part to an initial preference for “more.” On transfer trials involving all possible pairings of the training cards, subjects generally performed as though their choices were governed by the concept “more” or “fewer”. This tendency increased with age and with experience in the situation, even though conditions made verbal mediation appear unlikely.     

Impact of Co-Therapy Teams on Client Outcomes and Therapist Training in Marriage and Family Therapy

This study of 33 student therapists, 402 client systems, and three supervisors tested the efficacy of using student co-therapy teams as an aspect of clinical training in a marriage and family therapy program. This study utilizes both quantitative and qualitative methodology. Two research questions were addressed: “Do different pairings of co-therapists affect client outcomes?” and “Is co-therapy a viable option for a training program?” The results indicate that client outcomes using co-therapy are at least as effective as treatment using one therapist and in some circumstances produce more positive outcomes for both clients and student therapists.     

Vibrotactile spatial summation

By means of a two-interval, forced-choice technique, absolute thresholds were obtained at several sites on the skin for short bursts of mechanical vibration. The difference between the energy required for a single vibrator, in dB, to reach threshold and the energy required for two vibrators presented successively to reach threshold was taken as the measure of probability summation. Spatial summation was computed as the difference between the energies required for threshold for the two vibrators presented successively and simultaneously. Both probability summation, 0.52 dB lowering in threshold, and spatial summation, 1.94 dB lowering in threshold, remained constant as a function of the distance between the two vibrators on the thigh. Similar amounts of summation were obtained unilaterally and bilaterally on the fingers. When the frequency of vibration was lowered to 9 Hz, no spatial summation was found. When the frequencies of vibration at the two test sites were different, 160 Hz at one locus, 360 Hz at the other locus, there was no spatial summation.     

Cardiovascular generalization and differentiation: The relationship between heart rate and blood pressure

The present study was designed to study generalization and differentiation and to check the relation between heart rate and blood pressure in cardiovascular conditioning. Five naive mongrel dogs were presented with 10 sec 1000 cps tone regularly reinforced with 0.5-sec shock to a left foreleg. Four other 10-sec tones (600, 800, 1200, 1400 cps), never reinforced, were administered in a randomized and counterbalanced fashion using a differential reinforcing technique. The response measures were heart rate and three indices of blood pressure,i.e., systolic, diastolic, and pulse pressures.“Initial response” of heart rate showed rapid tachycardia to all tones, with no generalization and differentiation among five tones.“Terminal response” clearly indicated generalization gradients that tachycardia to 800 and 1200 cps tones were higher than those to 600 and 1400 cps tones, respectively. Some differences were noted among systolic, diastolic, and pulse pressures, with pulse pressure showing a trend of generalization and differentiation in the“initial response.” No statistical difference, however, was obtained in blood pressure scores. Beat-by-beat analyses of correlations between heart rate and diastolic blood pressure showed that the correlations successively decreased during the“terminal response.” Overall correlations between heart rate and three indices of blood pressure were obtained, with the highest correlation between heart rate and pulse pressure. Considering the above results in relation to the classical conditioning theory, it was tentatively concluded that“initial response” includes non-conditional factors, while“terminal response” reflects mainly a true conditional response, particularly, at a long CS-US interval. This interpretation leads to the hypothesis that conditional response with a short CS-US interval may attain better conditioning scores in terms of the summation effect between a non-conditional factor and a true conditional factor.     

Retention and Recall: Incidental Learning of Visual and Auditory Material

This study examined the effect on observer agreement of switching from a system of overt reliability assessment to two successive systems of covert reliability measurement. A primary purpose was to see whether agreement obtained with the use of covert data checks would improve over time if observers were provided with accurate feedback regarding their level of agreement. Seventeen undergraduate psychology students served as Ss. They observed instructional interactions between preschool children and their teachers. During the two week “overt” check period (Phase I), observers were aware of when their observations were being “checked” by a previously designated reliability assessor. In the subsequent covert phases (weeks 3–7) this information was not available to them during the observational sessions. When covert monitoring was implemented, agreement rates initially dropped significantly below the “overt” measurement phase. Gradually agreement rates improved until, in weeks 6 and 7, they were not significantly different from the initial overt measures. Es should be aware that an overt check on observer agreement may not reflect the true reliability of an observational system. However, when observers are given accurate feedback on their level of agreement, they are able significantly to improve their vigilance and consistency in the use of the observational system.     

Summation of excitatory and inhibitory control produced by traditional tone-shock contingencies and autocontingencies

Previous research has demonstrated that rats can use unsignaled shock to predict subsequent periods free from shock. This shock-no shock stimulus arrangement, termed an autocontingency, has appeared less likely to exert behavioral control when a traditional tone-shock contingency was simultaneously available. The present research examined the generality of CS-US contingency dominance in a conditioned suppression paradigm by using a summation test in which “probe” stimuli derived from tone-shock contingencies were superimposed upon responding maintained by an autocontingency. In experiment 1, an inhibitory CS accelerated responding only when responding was normally suppressed by the autocontingency. In experiment 2, an excitatory CS failed to yield conditioned suppression during an inhibitory (accelerative) period produced by the autocontingency. Unlike our previous findings (e.g., Davis, Memmott & Hurwitz, 1975), these results do not support a general notion of tone-shock contingency dominance over autocontingencies. Behavioral control by autocontingencies appears robust and “holds its own” in summation with both excitatory and inhibitory CSs derived from traditional contingencies.     

Reaction times and error rates for judging nominal identity of letter strings

Most theories of “same”-“different” judgments predict that “same” responses should be at least as slow as “different” responses. However, the contrary has often been found. To explain this, a two-processor model has been proposed. In this model, a fast processor and a slow processor operate simultaneously. “Same” responses are initiated by whichever processor first indicates that the stimuli are “same,” whereas “different” responses are initiated only by the slow processor. In the experiment reported here, Ss judged whether two successively presented letter strings were nominally “same” or “different.” It was expected that the fast processor would be incapable of making nominal identity judgments. Thus, both “same” and “different” responses would be initiated by the slow processor. Consequently, “same” responses should have been slower than “different” responses. However, this did not occur. This finding casts doubt upon, but does not disprove, the two-processor model.