Male versus female Siamese fighting fish as reinforcing stimuli for conspecific males in single- and two-choice operant situations

Two experiments attempted to determine the reinforcing effectiveness of visual exposure to a female versus a male stimulus in male Siamese fighting fish (Betta splendens). This was accomplished by making male or female presentation contingent upon an operant ring swimming response in single- (Experiment 1) and two-choice (Experiment 2) continuous reinforcement operant situations for 1 hr per day. It was found that visual exposure to a female stimulus was behaviorally reinforcing in a way comparable to that typically found in intermale studies. If given a choice, male test subjects were observed to demonstrate a consistent preference for the female as opposed to the male stimulus. The results are discussed in terms of stimulus discrimination and approach-avoidance conflict as differentially elicited by male and female target stimuli.     

Influence of neighborhood size and exposure duration on visual-word recognition: evidence with the yes/no and the go/no-go lexical decision tasks

We present two experiments in which we measured lexical decision latencies and errors to words with few or many orthographic neighbors (ie., Coltheart's N). The main goal of the study was to examine whether or not the neighborhood size effect in a lexical decision task could be affected by the exposure duration of the stimulus item (unlimited vs. limited time exposure, 150 msec plus a backward mask) and the type of decision involved in the task (yes/no vs. go/no-go lexical decision tasks). In the yes/no task, the results showed a facilitative neighborhood size effect for low frequency that did not interact with exposure duration (Experiment 1). In contrast, in the go/no-go task (in this task, participants are instructed to respond as quickly as they can when a word is presented and not to respond if a nonword is presented), the neighborhood size effect for low-frequency words (and for nonwords) was greater under limited viewing time (Experiment 2). In addition, the word frequency effect was greater in the go/no-go task than in the yes/no task, replicating Hino and Lupker (1998, 2000). The results were interpreted in terms of the interaction of decision and lexical factors in visual-word recognition.     

Sub-Optimal Choice by Pigeons: Failure to Support The Allais Paradox

Pigeons show a preference for an alternative that provides them with discriminative stimuli (sometimes a stimulus that predicts reinforcement and at other times a stimulus that predicts the absence of reinforcement) over an alternative that provides them with nondiscriminative stimuli, even if the nondiscriminative stimulus alternative is associated with 2.5 times as much reinforcement (Stagner & Zentall, 2010). In Experiment 1 we found that the delay to reinforcement associated with the nondiscriminative stimuli could be reduced by almost one half before the pigeons were indifferent between the two alternatives. In Experiment 2 we tested the hypothesis that the preference for the discriminative stimulus alternative resulted from the fact that, like humans, the pigeons were attracted by the stimulus that consistently predicted reinforcement (the Allais paradox). When the probability of reinforcement associated with the discriminative stimulus that predicted reinforcement was reduced from 100% to 80% the pigeons still showed a strong preference for the discriminative stimulus alternative. Thus, under these conditions, the Allais paradox cannot account for the sub-optimal choice behavior shown by pigeons. Instead we propose that sub-optimal choice results from positive contrast between the low expectation of reinforcement associated with the discriminative stimulus alternative and the much higher obtained reinforcement when the stimulus associated with reinforcement appears. We propose that similar processes can account for sub-optimal gambling behavior by humans.     

Newborns' preference for faces: what is crucial?

Three experiments investigated whether the presence of more elements in the upper part of a configuration (i.e., up-down asymmetry) plays a role in determining newborns' preference for facelike patterns. Newborns preferred a nonfacelike stimulus with more elements in the upper part over a nonfacelike stimulus with more elements in the lower part (Experiment 1), did not show a preference for a facelike stimulus over a nonfacelike configuration equated for the number of elements in the upper part of the configuration (Experiment 2), and preferred a nonfacelike configuration located in the upper portion of the stimulus over a facelike configuration in the lower portion of the pattern (Experiment 3). Results demonstrated that up-down asymmetry is crucial in determining newborns' face preference.     

The two-alternative observing response procedure in rats: Preference for nondiscriminative stimuli and the effect of delay

A two-alternative choice procedure was used with rats to examine preference for discriminative stimuli (correlated with the occurrence of reinforcement) versus uncorrelated cues. Choice of discriminative stimuli was below chance, despite the use of very low levels of reinforcement (12.5% for some rats) known to produce a preference for discriminative cues. Levers that had been retracted during the stimulus presentation in Experiment 1 were extended in Experiment 2 to assess the role of response elicitation during the observed stimuli. In Experiment 3, the impact of cue-duration behaviors was further evaluated by lengthening the duration of the cues and providing an opportunity for an escape response. The preference for nondiscriminative stimuli was reversed only with increased exposure to the cues. The present results point to fundamental differences in the prevailing context of the choice procedure as compared to the usual free-operant observing design.     

Self-control in rhesus macaques (Macaca mulatta): controlling for differential stimulus exposure

Previous research on self-control using macaques (Macaca fascicularis) showed these animals have a strong bias for a delayed, larger reinforcer (Self-control) over an immediate, smaller reinforcer (Impulsive). Typical studies of self-control have used a discrete trials methodology with a secondary discriminative stimulus during the delay periods. This results in a greater exposure to the stimulus representing the self-controlled option and may account for some of the early exclusive preference for self-control observed. The present experiment examined self-control bias in three rhesus macaques (Macaca mulatta) while controlling for differential durations of stimulus exposure. Subjects were presented stimuli via a computer monitor and made choices by touching the stimulus at which point both stimuli were removed for the delay periods. All three subjects displayed a nearly exclusive bias for the delayed, larger reinforcer self-control). These results are consistent with previous studies, despite the variations in methodology and species.     

The influence of a distractor during compound preexposure on latent inhibition

Nonreinforced exposure to a nontarget stimulus that was followed by nonreinforced exposure to a target/nontarget simultaneous compound stimulus resulted in enhanced latent inhibition of the target. Conditioning was slower after this treatment than after nonreinforced exposure to the target stimulus alone (Experiment 1). However, a salient auditory stimulus presented immediately after the compound in the second phase reduced levels of latent inhibition, relative to the enhanced latent inhibition produced when no such extracompound stimulus was presented (Experiments 2 and 3). This effect was not noted if the salient auditory cue was presented 10 sec after the termination of the compound stimulus (Experiment 4). In Experiment 5, there was no disruption of simple latent inhibition produced by a salient stimulus. These results are consistent with enhanced latent inhibition's being produced by the formation of within-compound associations, which are disrupted by the salient extracompound stimuli.     

Social chemosignals in five Belontiidae (Pisces) species

Approach behaviors toward conspecific chemical stimuli of the opposite sex were examined in five Belontiidae species: Betta splendens, Macropodus opercularis, Colisa labiosa, C. lalia, and Trichogaster trichopterus. Approach was measured by (a) preference for section 1 of a three-section tank, which contained a vertical tube that introduced the stimulus water, and (b) occupancy of the tube. Experiments 1A and 1B showed that (a) approach behaviors were displayed by the isolated male Betta only to ripe-female stimulus water, (b) group-housed males of the remaining four species were not attracted to female-conditioned water, and (c) socially isolated males of these four species preferred section 1 during presentation of either ripe- or nonripe-female-inhabited water but occupied the tube only during exposure to ripe-female-conditioned water. The findings of Experiment 2A were that (a) the female Betta, regarless of physiological state, showed approach behaviors to male-inhabited water and (b) only ripe females of the remaining species indicated a preference for section 1 during male-water exposure but performed no tube entries. Results of Experiment 2B indicated that social isolation of the females, especially ripe females, facilitated their approach behaviors.     

Preference for the outcome that follows a relatively aversive event: Contrast or delay reduction?

Pigeons prefer a positive discriminative (S+) stimulus that follows a less preferred event (a large number of required responses, a longer delay, or the absence of food) over a different S+ with a similar history of reinforcement that follows a more preferred event (a single required response, no delay, or food). We proposed that this phenomenon results from contrast (referred to as within-trial contrast) between the less preferred initial event and the signal for reinforcement. Delay reduction theory (Fantino, 1969) can account for these results by proposing that the less preferred initial event lengthens the duration of the trial, thereby allowing the S+ stimulus to occur later in the trial and thus become a better predictor of reinforcement. In the present experiments, we further explored this effect. In Experiment 1, we controlled for trial duration by using a fixed ratio response (30 pecks) as one initial event and the absence of pecking for the same duration as the other initial event (0 pecks). The pigeons showed a reliable preference for the positive stimulus that followed the least preferred initial event. In Experiment 2, we controlled for trial duration by using 30 pecks as one initial event and 1 peck followed by a delay that matched the duration of the preceding 30-peck trial. (Group Time Same). For Group Time Different, there was no delay following the 1-peck initial event. For Group Time Same, preference for the initial event negatively predicted the pigeons’ preference for the S+ stimulus that followed, supporting the contrast account. A somewhat greater preference for the discriminative stimulus that followed the least preferred initial event was found for Group Time Different suggesting that in addition to contrast, delay reduction also may play a small role. However, the greater initial-event preference found for Group Time Different suggests that contrast can account for the group difference as well.     

Extinction of Within-event Learning Is Contextually Controlled and Subject to Renewal

Five experiments examined within-event learning in rats by inducing an appetite for one of the elements (salt) of a compound stimulus and assessing preference for the other element (almond). Almond preference was conditional upon (1) the almond flavour having been presented in compound with the salt, and (2) the assessment being conducted when the rats were out of sodium balance (Experiment 1). Presentations of the compound in one environment (A) and of the salt and almond elements in a second environment (B) resulted in greater almond preference when rats were tested in A than in B (Experiment 2). Almond preference was reduced when separate presentations of the compound and almond (Experiment 3) or of the compound and salt (Experiment 4) occurred in the same environments but not when these presentations occurred in different environments. Rats exposed to the compound in A and then extinguished to the elements in either A or B showed a reduced almond preference when tested in the extinction environment, but not when tested in the other environment (Experiment 5). Thus, extinction of within-event learning is context-specific and subject to renewal. The results were interpreted in terms of an associative model whereby separate presentations of the elements result in a symmetrical inhibitory link which is contextually gated (Bouton, 1993).     

How bumblebees first find flowers: Habituation of visual pattern preferences, spontaneous recovery, and dishabituation

Two experiments examined the exploratory behaviour of flower-naïve bumblebees. Bees were tested four times in a 12-arm radial arm maze in which they never received reward. Patterned and unpatterned stimuli were presented at the end of each corridor and the choices of the bees were recorded. We examined the effects of two variables, time and the presentation of a new stimulus, on habituation to a visual pattern. In Experiment 1, once bees had shown an unlearned preference for a pattern, and the preference had habituated, a response decrement was maintained after a confinement in the colony of two hours. After a 24 h confinement, however, the pattern preference was restored, i.e., spontaneous recovery was observed. In Experiment 2, the presentation of a new stimulus triggered renewed responding to the old pattern to which the bees had habituated, i.e., dishabituation was observed. Habituation to visual patterns is modulated by time and by exposure to new stimuli so that exploration in the face of failure to find food persists and unrewarding visual patterns are not eliminated for long as possible sources of food.     

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.     

Stimulus control of behavioral history.

Pigeons were exposed to two different reinforcement schedules under different stimulus conditions in each of two daily sessions separated by 6 hr (Experiments 1 and 2) or in a single session (Experiment 3). Following this, either a fixed-interval (Experiment 1) or a variable-interval schedule (Experiments 2 and 3) was effected in both stimulus conditions. In the first two experiments, exposure to fixed-ratio or differential-reinforcement-of-low-rate schedules led to response-rate, but not pattern, differences in subsequent performance on fixed- or variable-interval schedules that persisted for up to 60 sessions. The effects of reinforcement-schedule history on fixed-interval schedule performance generally were more persistent. In Experiment 3, a history of high and low response rates in different components of a multiple schedule resulted in subsequent response-rate differences under identical variable-interval schedules. Higher response rates initially occurred in the component previously correlated with high response rates. For 3 of 4 subjects, the differences persisted for 20 or more sessions. Previous demonstrations of behavioral history effects have been confined largely to between-subject comparisons. By contrast, the present results demonstrate strong behavioral effects of schedule histories under stimulus control within individual subjects.     

Reinforcement of inhibitory positional priming by spatial working memory contents

This study examined whether positional priming of pop-out is modulated by spatial working memory (WM). In Experiments 1A and 1B, observers were presented with a to-be-memorized item (Experiment 1A: triangle; Experiment 1B: circle) prior to performing a block of search trials, with triangular stimulus configurations (one target, two distractors) on an underlying elliptical frame. Each search block was followed by a memory test (i.e., memory conditions). In Experiment 1C, the presentation of the memory item (triangle) was immediately followed by the memory test, and the search block was performed after this test (i.e., no-memory condition). It was found that targets presented at a previous target were detected faster and targets presented at a previous distractor location slower, relative to a previous empty (‘neutral’) stimulus location, respectively. While facilitatory position priming was uninfluenced by the memory manipulation, inhibitory positional priming was larger in the memory than no-memory condition, but only when the memory stimulus (triangle) matched the (triangle) configuration formed by the three search items. This finding of larger inhibitory priming under memory conditions provides further evidence that positional priming, rather than being purely bottom-up determined, is open to top-down influences.     

Choice of extinction-signalling stimuli by rats

Rats in a two-lever situation were exposed to alternating periods of intermittent reinforcement and extinction. Extinction periods were either unsignalled or were signalled by a response-produced stimulus. The signal was sometimes a stimulus paired with food delivery in the reinforcement periods and sometimes a stimulus that occurred only in extinction periods. Both kinds of signal accelerated extinction relative to the unsignalled condition. When the signal was the stimulus paired with food in reinforcement periods, the rats tended to prefer the lever that gave that signal even though the signal accelerated extinction. There was no comparable effect for the stimulus that occurred only in extinction periods; when this signal was contingent on only one of the two levers, the rats either avoided it (Experiment 3) or were indifferent (Experiment 4). It is concluded that a stimulus can be a “secondary reinforcer” as measured by preference, even though it decreases resistance to extinction; the implications are discussed with reference to formal theories of choice behavior.     

Generalization and response latency

The present experiments investigated generalization in a reaction time situation where the generalization stimulus, a tone, preceded the reaction time signal, a light. The hypotheses under investigation were that the duration of the cue stimulus would determine the degree of generalization (Experiment I) and that the response latency independent of the stimulus duration would be related to the amount of generalization (Experiment II). A particular generalization test stimulus (a tone of 40, 45, 50, 60, 65, or 70 dB) was presented only once always following two bar-pressing responses to training stimulus (tone of 55 dB) under each of two conditions of stimulus duration in Experiment I and under each of two conditions of response latency in Experiment II. It was found that under the condition of short response latency generalization was broader.     

Generalization and response latency

The present experiments investigated generalization in a reactio? time situation where the generalization stimulus, a tone, preceded the reaction time signal, a light. The hypotheses under investigation were that the duration of the cue stimulus would determine the degree of generalization (Experiment I) and that the response latency independent of the stimulus duration would be related to the amount of generalization (Experiment II). A particular generalization test stimulus (a tone of 40, 45, 50, 60, 65, or 70 dB) was presented only once always following two bar-pressing responses to training stimulus (tone of 55 dB) under each of two conditions of stimulus duration in Experiment I and under each of two conditions of response latency in Experiment II. It was found that under the condition of short response latency generalization was broader.     

The effects of presentation time on preference for curvature of real objects and meaningless novel patterns

Objects with curved contours are generally preferred to sharp‐angled ones. In this study, we aim to determine whether different presentation times influence this preference. We used images of real objects (experiment 1) and meaningless novel patterns (experiment 2). Participants had to select one of two images from a contour pair, curved and sharp‐angled versions of the same object/pattern. With real objects, the preference for curved versions was greatest when presented for 84 ms, and it faded when participants were given unlimited viewing time. Curved meaningless patterns were preferred when presented for 84 and 150 ms. However, in contrast to real objects, preference for meaningless patterns increased significantly in the unlimited viewing time condition. Participants discriminated poorly between the two versions (curved and sharp‐angled) of the meaningless patterns in the 84‐ and 150‐ms presentations (experiment 3). Therefore, in short times with meaningless patterns, participants selected mostly the curved version without being aware of the difference. In conclusion, presentation time, type of stimulus, and their interaction influence preference for curvature.     

Preference for tones as a function of frequency (hertz) and intensity (decibels)

An extension of the Wundt hypothesis concerning stimulus intensity and hedonic tone leads to the prediction that Ss prefer tones of intermediate frequency (hertz) and of intermediate intensity (decibels). In Experiment 1, tones varying from 60 to 5000 Hz were presented in a paired comparison procedure, and, as predicted, Ss′ preference was an inverted-U-shaped function of frequency, with the most preferred tones in the range of 400–750 Hz. In Experiment 2, tones varying in intensity from 40 to 90 dB were also presented in a paired comparison procedure, and again the predicted inverted-U-shaped preference function was found, with 50 dB as the preferred intensity. Related research and some unexpected findings are discussed.     

A comparison of displacement and reinforcer potency for typically developing children

Previous researchers found that individuals with intellectual and developmental disabilities tend to prefer edible over leisure stimuli, although leisure stimuli may still function as reinforcers. We replicated and extended previous research in a 2-part experiment with typically developing children. In Experiment 1, we evaluated 15 children's preference for leisure and edible stimuli. Five of 15 participants preferred edible over leisure stimuli, 3 of 15 participants preferred leisure over edible stimuli, and the remaining 7 of 15 participants did not show a preference for a stimulus class. In Experiment 2, we compared the reinforcer potency of the top-ranked stimulus from each class with 7 of the 8 participants who showed displacement of one stimulus class. Four of 7 participants allocated more responding to the task associated with the top-ranked stimulus and 3 of 7 participants showed no differences in responding to the task regardless of the stimulus rank.