Performance of pigeons on delayed simple and conditional discriminations under equivalent training procedures

A pair of experiments investigated the short-term memory of pigeons under delayed simple and conditional discriminations. Trial sequences in both discriminations consisted of a color as the sample stimulus, a memory interval, a line orientation as the test stimulus, and a trial outcome, which was either food reinforcement or blackout. Pecking rates during the test stimulus defined discrimination performance. In the simple discrimination, the sample provided the necessary information regarding the subsequent trial outcome. In the conditional discrimination, the sample and test stimuli conjointly provided this information. In Experiment 1, the two procedures were compared with independent groups of pigeons. In Experiment 2, the comparison was made within subjects. The simple discrimination was acquired more quickly and was performed better with a memory requirement. Introduction of long delays disrupted performance even at shorter delays in both discriminations. Postulation of prospective as well as retrospective mediating processes facilitates the interpretation of these results.     

Assessment of the relative importance of S+ and S− in rats using differential training on intercurrent discriminations

The present studies assessed the degree of stimulus control exerted by S+ and S? without confoundings of stimulus novelty and stimulus ambiguity. In Experiment 1, rats were trained on two intercurrent simultaneous discrimination problems with nine times more training given on one than the other. Then the animals were given transfer tests with re-paired stimuli. The results showed that S? exerts greater stimulus control than S+ in a two-choice simultaneous discrimination. Experiment 2 provided a test of the possibility that the relative degree of control by S? varies with different amounts of training. Three groups were trained on two intercurrent simultaneous discrimination problems; each group was given 7, 11, or 15 times more training on one problem than the other. Then transfer tests were given with re-paired stimuli. Again the results showed that S? exerts greater stimulus control than S+ in a two-choice simultaneous discrimination.     

Psychophysical scaling of stimulus similarity in 3-month-old infants and adults

The ability of 3-month-old infants to discriminate novel components of a prefamiliarized stimulus was assessed using an operant paradigm. Subjects were familiarized with the standard stimulus (five-component mobile) in three daily conditioning sessions and then were exposed to a comparison mobile containing from zero to four novel components substituted for familiar elements at the outset of a fourth daily session. Although a reliable reduction in mean number of footkicks was found only when an extreme number of components was substituted, log-log plots of infant response as a function of degree of novelty indicated that discriminability was described by a power function. Adult judgments of the similarity between the standard mobile and each degree of novelty were also described by a power function, suggesting a common basis may underlie the perception of similarity in the two groups. The finding of a power function for infant response to visual novelty is consistent with reports of similar discriminability functions in infant olfaction and audition. However, duration of visual fixation increased nondifferentially to all test stimuli, irrespective of degree of novelty. The latter finding is inconsistent with predictions arising from the visual attention literature.     

Delayed recognition memory for orientation by human infants

The familiarization/novelty preference paradigm was employed to study the effect of a delay (between the end of the familiarization phase and the beginning of the test phase) on discrimination of the orientation of square-wave gratings by 2- and 3-month-old human infants. Three stimulus pairs were studied: horizontal-vertical, non-mirror-image obliques, and mirror-image obliques. The data indicate that the members of the oblique-oblique stimulus pairs are confused in memory to a greater extent than the members of the horizontal-vertical stimulus pair. These findings are consistent with P.C. Bomba's (1984, Journal of Experimental Child Psychology, 37, 609-636) recent report that infants respond to the orientation of a visual stimulus in a categorical-like manner.     

Contribution of the dorsal subiculum to memory for temporal order and novelty detection using objects,odors, or spatial locations in the rat

The contribution of the dorsal subiculum (DS) to memory for temporal order and novelty detection was assessed using a spontaneous exploration paradigm with objects (visual/tactile stimuli), odors, or spatial locations (Hunsaker, Fieldsted, Rosenberg, & Kesner, 2008). Rats with selective excitotoxic lesions of the DS were compared to sham-operated rats (SHAM) in the two exploration tests. In temporal order tests, two previously explored stimuli were presented and normal rats typically show a preference for exploring the stimulus that was first explored compared to the other stimulus. In novelty detection tests, a familiar and a new stimulus were presented and normal rats typically have a preference for exploring new stimuli. In temporal order tests, results indicated that Group SHAM explored significantly more the first than the last stimulus they met when the stimuli were odors or objects. In addition, SHAM rats predictably displayed a significant preference for the new stimulus in the novelty detection tests with objects, odors, and spatial locations. Group DS did not differ from controls on the temporal order and the novelty detection tests with objects or odors. However, on the novelty detection test with spatial locations, Group DS differed from Group SHAM. These results suggest that the DS is necessary for the memory of spatial locations but not of objects and odors.     

Reasoning by exclusion in the kea (<Emphasis Type="Italic">Nestor notabilis</Emphasis>)

Reasoning by exclusion, i.e. the ability to understand that if there are only two possibilities and if it is not A, it must be B, has been a topic of great interest in recent comparative cognition research. Many studies have investigated this ability, employing different methods, but rarely exploring concurrent decision processes underlying choice behaviour of non-human animals encountering inconsistent or incomplete information. Here, we employed a novel training and test method in order to perform an in-depth analysis of the underlying processes. Importantly, to discourage the explorative behaviour of the kea, a highly neophilic species, the training included a large amount of novel, unrewarded stimuli. The subsequent test consisted of 30 sessions with different sequences of four test trials. In these test trials, we confronted the kea with novel stimuli that were paired with either the rewarded or unrewarded training stimuli or with the novel stimuli of previous test trials. Once habituated to novelty, eight out of fourteen kea tested responded to novel stimuli by inferring their contingency via logical exclusion of the alternative. One individual inferred predominantly in this way, while other response strategies, such as one trial learning, stimulus preferences and avoiding the negative stimulus also guided the responses of the remaining individuals. Interestingly, the difficulty of the task had no influence on the test performance. We discuss the implications of these findings for the current hypotheses about the emergence of inferential reasoning in some avian species, considering causal links to brain size, feeding ecology and social complexity.     

Long-term memory in pigeons: I. The role of discrimination problem difficulty assessed by reacquisition measures II. The role of stimulus modality assessed by generalization slope

Pigeons learned either an easy or a difficult line angle discrimination (Experiment 1) or wavelength discrimination (Experiment 2), and then they were given a reacquisition test of retention after delays of 1 min, 1 day, or 1 week. Both percentage of responses to the S+ in the initial 10-trial block and number of blocks to criterion showed a progressive memory loss which was greater for the difficult problem. These results extend recent findings by using a free operant rather than a discrete trial task and by varying problem difficulty by altering the dimensional separation between training stimuli. In Experiment 3, pigeons were given variable interval training with either a wavelength or a line angle stimulus, and then they were tested for generalization in extinction after delays of 1 min, 1 day, and 1 week. With both dimensions, the relative gradients became progressively flatter with increasing delay intervals. This replicates earlier findings and extends them to the line angle dimension. The evidence of substantial forgetting in the first 24 h in all three experiments suggests that operant free-response procedures are more sensitive to forgetting effects than are discrete trial tasks.     

Stigma,staring, and discomfort: A novel-stimulus hypothesis

Three experiments were conducted in order to assess the validity of the novel-stimulus hypothesis as an explanation for why people who are physically different (i.e., novel) are avoided. The hypothesis states that avoidance is mediated by conflict over a desire to stare at novel stimuli and a desire to adhere to a norm against staring when the novel stimulus is another person. In the first two field experiments, subjects viewed photographs of novel (handicapped or pregnant) and familiar (physically normal) people under conditions where staring was sanctioned or not. It was found that staring increased with novelty when staring was unobserved (sanctioned); however, the reverse obtained when an observer was present. In the third experiment, subjects interacted with a crippled, pregnant, or physically normal partner. Half of the subjects were first given the opportunity to observe their partner through a one-way mirror. The reduction in stimulus novelty for this group resulted in reduced avoidance. The question of whether such avoidance of the disabled results from feelings of dislike or disgust as previously suggested, or from discomfort created by novelty, is discussed.     

S+ versus S− Fading in prompting procedures with autistic children

The purpose of this investigation was to assess the relative effectiveness of two prompt-fading procedures for teaching difficult visual discriminations to autistic children. Both prompt procedures involved within-stimulus fading where manipulation occurred on the relevant component of the discrimination. One procedure involved fading first along the S+ stimulus, while holding the S? stimulus constant. The other procedure involved fading first along the S? stimulus, while holding the S+ stimulus constant. Eight autistic children were each taught two discriminations, one by each of the prompt procedures. Results indicated that for all but one child, the discriminations were acquired significantly faster, with fewer errors, when the S+ stimulus was faded first. These findings are related to the literature on the effects of stimulus novelty on selection and learning.     

Linear Position Preference Habits of Monkeys

While novelty is well established as a motivational factor in children's preferences, the methodology with which the effect is demonstrated seems poorly equipped to deal with the issue of the strength of novelty, since choices alternatives have frequently been limited to items of comparable base attractiveness. Data, drawn from 216 first graders, are reported for a procedure in which stimulus unattractiveness was pitted against novelty to test the capacity of this variable to sway Ss' choices in the presence of resistance. Consistent with previous findings, it is shown that roughly 80% of preschoolers chose a novel item rather than a familiar one when the alternatives were comparably desirable except for the element of novelty. However, when a difference in base attractiveness favored the familiar item, novelty choice dropped sharply. Problems of specification of the strength of novelty and interpretation of observed levels of novelty preference are discussed in terms of the methodology of choice research with children. The motivational strength of novelty for children is questioned.     

Pupillary changes during recall in children

Seven children aged 7–9 years were auditorily presented five-digit numbers for retention intervals of 0 and 10 sec. Pupil size was recorded during stimulus presentation, retention interval, and recall of items. Findings indicate that pupil dilation occurs during encoding and retrieval of stimulus items with pupillary constriction occurring during retention of the items. The pupillary change functions obtained with children were found to be very similar to those obtained with older subjects.     

New evidence for infant colour categories

Bornstein, Kessen, and Weiskopf (1976) reported that pre‐linguistic infants perceive colour categorically for primary boundaries: Following habituation, dishabituation only occurred if the test stimulus was from a different adult category to the original. Here, we replicated this important study and extended it to include secondary boundaries, with a crucial modification: The separations between habituated and novel stimuli were equated in a perceptually uniform metric (Munsell), rather than in wavelength. Experiment 1 found Categorical Perception and no within‐category novelty preference for primary boundary blue‐green and secondary boundary blue‐purple. Experiment 2 replicated the categorical effect for blue‐purple and found no within‐category novelty preference with increased stimulus separation. Experiment 3 showed category effects for a lightness/saturation boundary, pink‐red. Novelty preference requires a categorical difference between the habituated and novel stimulus. The implications for the origin of linguistic colour categories are discussed.     

The nature of standard control in children's matching-to-sample

In Experiment I, six preschool-aged children were given matching-to-sample training with two figures in which they were required to choose one of two comparison stimuli that was identical in shape to the standard stimulus. Following this training, they were given intermittent test trials in which a novel stimulus figure was substituted for the previously correct comparison stimulus. Five of the six subjects consistently chose the substituted stimulus during test trials. Experiment II replicated the findings of Experiment I with three other preschool-aged children. Experiment II also provided controls for the possibility that the subjects of Experiment I were selecting the substituted stimulus because of its novelty. The investigators concluded that eight of the nine subjects were exhibiting the type of control described by Berryman, Cumming, Cohen, and Johnson (1965) as S-delta responding.     

Development of chromatic induction in infancy

The perception of colour in an embedded field is affected by the surround colour. This phenomenon is known as chromatic induction. In the present study we investigated whether the colour perception by infants aged 5–7 months could be affected by the surround colour. In Experiments 1 and 2 each stimulus was composed of an array of six squares in tandem. The colour appearance of the array in the familiarization stimulus was established by chromatic induction. In Experiment 1 we used familiarization stimuli that were perceived as two‐colour array with a two‐colour surround. In Experiment 2 we used a familiarization stimulus that was perceived as a uniform‐colour array with a two‐colour surround. In the test phase, the uniform‐colour array and the two‐colour array were presented on a white uniform‐colour surround in both experiments. The results showed that in Experiment 1 the 5‐ and 7‐month‐old infants had novelty preference for the uniform‐colour test array. This suggested that the infants' colour perception could be affected by surround colour. The results of Experiment 2 showed that the 7‐month‐olds showed a novelty preference for the two‐colour test array, but the 5‐month‐olds showed no novelty preference. This suggested that 7‐month‐olds' colour perception could be affected by surround colour, but that of 5‐month‐olds could not. We discuss the contradiction of the results between Experiments 1 and 2. Copyright © 2007 John Wiley & Sons, Ltd.     

Feeding-based arousal effects on visual recognition memory in early infancy.

Arousal effects on a 1-trial visual recognition paired-comparison task were studied at newborn, 1-month, and 4-month test ages. Infants were tested before and after feeding, with arousal assumed to be lower after feeding. Newborns and 1-month-olds shifted from a familiarity preference before feeding to a novelty preference after feeding. A control group tested only after feeding confirmed that this shift was not due to increased stimulus exposure from the prefeeding test. By 4 months, infants showed novelty preferences independent of feeding. This age by arousal interaction for recognition memory extends previous knowledge by including endogenous arousal with age, stimulus, and length of exposure as contributors to familiarity-novelty preferences. It also extends and provides converging evidence for arousal effects on visual attention in early infancy found previously with preferential looking. A shift from subcortical to cortical dominance is supported.     

Children's preference for novelty in selective learning: Developmental stability or change?

Data relating novelty preference to age for normal children are inconsistent, although a current theory predicts a developmental shift from novelty to familiarity preference in selective learning (D. Zeaman, 1976, in T. J. Tighe & R. N. Leaton (Eds.), Habituation: Perspectives from child development, animal behavior, and neurophysiology (pp. 297–320), Hillsdale, NJ: Erlbaum). Support for this theory, however, has been derived primarily from studies of retardate learning. Normal children's novelty preference was examined within a modified Moss-Harlow (E. Moss & H. F. Harlow, 1947, Journal of Comparative and Physiological Psychology, 40, 333–342) design to compare Zeaman's model with that of S. L. Witryol and W. Wanich (1983, The Journal of Genetic Psychology, 143, 3–8). Each of 16 problems, consisting of three single-stimulus demonstration trials and one two-choice test, was administered to 180 children (mean CA 4, 5.5, and 7 years) in three reward conditions. Novelty was manipulated by varying stimulus familiarization in the demonstration trials. Experiment 1 showed strong preferences for novel over familiar (demonstrated) stimuli at each age. Experiment 2 revealed novelty preference across age levels, two levels of reward contrast, and two levels of task difficulty. It was reasoned that Moss-Harlow tasks designed for normal children typically present a much higher level of difficulty than that intended by researchers. Furthermore, developmental decreases in novelty preference by retardates may derive from (a) transfer of training from prior experiments and (b) specific, repetitive instructions which may have directed attention away from stimulus novelty.     

Novelty as a reinforcer for position learning in children

The stimulus-familiarization-effect (SFE) paradigm, a reaction-time (RT) task based on a response to novelty procedure, was modified to assess response for novelty, i.e., a response-reinforcement sequence. Ninetysix kindergarten children were familiarized on one of two colored lights. Then Ss were confronted with a simple position discrimination task in which they could choose between two response buttons which produced either the previously familiarized light or a new (i.e., novel) light. Results showed that the choice response for the novel stimulus (NS) was facilitated by three variables: number of exposures to and duration per exposure of the familiar stimulus (FS), and degree of change provided by the NS relative to the FS. The parallel between the effective variables of this study and those which produce the SFE was noted, implicating an attention interpretation of the function of novelty as a reinforcer. The potential implications of attention for reinforcement theory and learning in general are discussed.     

外观新颖性对消费者购买意愿的影响：自我建构与产品类型的调节效应

外观创新在市场竞争中的地位越来越突出,然而因此而导致的成败案例都很普遍。如何进行外观创新更受消费者欢迎,其内在机制是什么,我们却知之甚少。基于独特性需求理论、风险感知理论及自我建构理论,本文探讨了自我建构与外观新颖性对消费者购买意愿的交互作用、影响机制以及边界条件。通过3个实验,发现对于独立型自我建构的消费者而言,高外观新颖性能引发独特性需求从而提高购买意愿,而对于相依型自我建构而言,低外观新颖性则通过降低社会风险感知从而提高购买意愿;同时,本文也确定了产品类型对该机制的调节作用,具体来讲,对于实用品,所有消费者都对低外观新颖性产品具有更强的购买意愿,而对于享乐品,所有消费者都对高外观新颖性产品具有更强的购买意愿。     

The ambiguous-cue problem: The effects of reduced similarity between trials and the schedule of reinforcement

In a series of seven experiments pigeons were trained on the two-choice ambiguous-cue problem that contains PA and NA trials. On PA trials choice of P (the positive stimulus) was reinforced and choice of A (the so-called ambiguous stimulus) was not reinforced; on NA trials choice of A was reinforced and choice of N (the negative stimulus) was not reinforced. When the two types of trials were distinguished by only the presence of P or N and each trial was terminated by one response, subjects quickly attained high levels of performance on NA trials but showed only chance levels of performance on PA trials. PA performance was markedly improved when a variety of additional stimuli distinguished the two types of trials and when a variety of schedules of intermittent reinforcement were employed; these manipulations had little effect on NA performance.     

A response rule for positive and negative stimulus interaction in associative learning and performance

The present article presents a response rule developed to account for both positive and negative stimulus interaction. In the response rule proposed here, positive interaction phenomena (e.g., second-order conditioning) and negative interaction phenomena (e.g., Pavlovian conditioned inhibition) are presumed to occur during performance and acquisition, respectively. Also, in this rule the novelty of the test stimulus determines the expression of positive interaction on responding. As the stimulus loses its novelty over training, positive interaction effects will wane, which will allow negative interaction effects to emerge in responding elicited by the stimulus. It is proposed that this response rule can be adopted by acquisition-focused associative models (e.g., Rescorla & Wagner, 1972) in order to account for contrary associative phenomena in the literature. The simulation program used in this study is available for download from the author’s website and from the Psychonomic Society website at www.psychonomic.org/archive.