Amount consumed varies as a function of feeder design.

Studies of pigeon behavior in which magazine-cycle duration is varied suggest that many researchers assume that feeders of different designs dispense food at roughly the same rate. However, Epstein (1981) showed that, with a commonly used feeder, the amount of grain a pigeon consumes is a negatively accelerated function of magazine-cycle duration. The present experiment shows that, with a different commonly used feeder, amount consumed is roughly a linear function of magazine-cycle duration. At a duration of 60 seconds, the second feeder dispenses roughly 10 times as much food as the first. Thus, reports of studies in which magazine-cycle duration is varied should identify the design of the feeder employed, and in some cases, authors should consider determining the feeding functions for those feeders.     

Subjective value of risky foods for individual domestic chicks: a hierarchical Bayesian model

For animals to decide which prey to attack, the gain and delay of the food item must be integrated in a value function. However, the subjective value is not obtained by expected profitability when it is accompanied by risk. To estimate the subjective value, we examined choices in a cross-shaped maze with two colored feeders in domestic chicks. When tested by a reversal in food amount or delay, chicks changed choices similarly in both conditions (experiment 1). We therefore examined risk sensitivity for amount and delay (experiment 2) by supplying one feeder with food of fixed profitability and the alternative feeder with high- or low-profitability food at equal probability. Profitability varied in amount (groups 1 and 2 at high and low variance) or in delay (group 3). To find the equilibrium, the amount (groups 1 and 2) or delay (group 3) of the food in the fixed feeder was adjusted in a total of 18 blocks. The Markov chain Monte Carlo method was applied to a hierarchical Bayesian model to estimate the subjective value. Chicks undervalued the variable feeder in group 1 and were indifferent in group 2 but overvalued the variable feeder in group 3 at a population level. Re-examination without the titration procedure (experiment 3) suggested that the subjective value was not absolute for each option. When the delay was varied, the variable option was often given a paradoxically high value depending on fixed alternative. Therefore, the basic assumption of the uniquely determined value function might be questioned.     

Treating food selectivity as resistance to change in children with autism spectrum disorder

Change-resistant behavior, such as rigid and selective food consumption, is a core symptom of autism that can have significant negative consequences for the child (Flygare Wallén et al., 2018; Levy et al., 2019). In the current study, we used a matching-law-based intervention (Fisher et al., 2019) to treat the change-resistant feeding behavior of 7 young children with autism. The feeder gave the participant a choice between a change-resistant and an alternative food during free- and asymmetrical-choice conditions. Alternative-food consumption increased for 2 participants during asymmetrical choice when the feeder provided a preferred item for consuming the alternative food and no programmed consequence for consuming the change-resistant food. Alternative-food consumption increased for the other 5 participants after the feeder exposed at least 1 food to single choice in which the feeder guided the participant to put the bite of alternative food in his or her mouth if he or she did not do so within 8 s of presentation. Effects of the single-choice contingencies maintained during reversals and generalized to other alternative foods the feeder did not expose to single choice. These results are important because participants consumed alternative foods even when their change-resistant foods were present, which is similar to typical mealtime contexts in which children have choices among foods.     

Measurement of consummatory behavior in honey bees

Consummatory behavior in honey bees can be measured by recording contact of the proboscis with sucrose solution in the food cup of an automatic feeder, and the behavior can be instrumentalized by arranging for contact of the proboscis with the food cup to activate the feeder. Illustrative free-operant and discrete-trials data are presented.     

Transfer of persistence to the acquisition of a new behaviour

Two experiments tested whether the degree of effort required for the reinforcement of one behaviour would affect the acquisition of a second behaviour. In the first experiment, rats were placed in a conditioning chamber and: (a) were required to press a lever for food pellets on a fixed ratio schedule, (b) received free presentation of the pellets, or (c) did not receive pellets. Next, all rats were rewarded for a new behaviour, round trips across the length of a runway. As predicted, the fixed-ratio group had the greatest shuttle rate. In the second experiment, two groups were required to press a lever, and the number of presses per pellet was varied. For two other groups not required to press the lever, the amount of food presented per approach to the feeder was varied. The greater required number of lever presses and the lesser number of pellets per approach to the feeder produced the higher subsequent shuttle rates. Two alternative explanations were compared: the degree of accustomed effort per reinforcer becomes a learned component of behaviour, or high effort increases the habituation of frustration-produced disruptive responses.     

An automated food delivery system for behavioral and neurophysiological studies of learning and memory in freely moving monkeys

We describe a custom-built feeder based on stepping motor technology controlled by a laboratory computer. The feeder dispenses a wide range of foods: any fruit, vegetable, or nut. The feeder allows the investigator to reward monkeys with different foods within a single experimental day. The monkey’s motivation to perform tasks is high and does not rely upon food regulation. The avoidance of regulation, as well as the palatability and variety of the rewards dispensed by our device, distinguishes it from commercially available products. We also describe the use of the feeder in the context of novel behavioral and neurophysiological studies in freely moving monkeys.     

Duration discrimination is better with food access as the signal than with light as the signal

In Experiment 1 a go/no-go discrimination procedure was used to compare control of five pigeons' keypecking by food-access duration with control by light duration. Pecks to an illuminated key were reinforced with grain following 10-sec presentations of food access or houselight, but not after 5-sec presentations of either stimulus. Each subject discriminated food-access duration faster and to a greater degree than light duration. In four between-subject replications, pigeons discriminated food-access duration better than the duration of a localized light, the feeder light and a keylight, and with either water or food as reinforcement. In Experiment 2 control by durations of food access and light was compared using a conditional right-left choice procedure (two pigeons), and a delayed symbolic matching-to-sample procedure (six pigeons). Under both, choice accuracy again was higher on food-access trials. The results of Experiment 3, in which two pigeons received generalization trials with durations of food access and light that were intermediate to the training values, confirmed that responding was controlled by the duration dimension of both food access and light. The superior control by food access is consistent with previous evidence that food is an effective and memorable stimulus, possibly because of its biological importance. These results also provided empirical support for the commonly made assumption that stimuli differ in effectiveness. As well, the results show that the stimulus to be discriminated can play an important role in the accuracy of duration disciminations, a fact which has implications for the study of temporal discriminations in animals.     

The disruption of autoshaped key pecking in the pigeon by food-tray illumination

Two experiments investigated the effect of food-tray illumination on pecking a lighted key that signalled food presentation. Pigeons key pecked less when both feeder and key stimuli preceded grain delivery than when the keylight alone signalled food. This detractive influence of grain-tray illumination did not result after prior pairings of the keylight with food. The involvement of associative and physical variables in autoshaping the pigeon's key peck is considered in light of these findings.     

Reliable operant apparatus for fish: Audio stimulus generator, response button, and pellet-dispensing nipple

As part of ongoing research into the ability of koi to categorize complex auditory stimuli, we have had to develop novel apparatus. The stimulus generator presents sound from two CD drives under computer control through a new underwater speaker. The operant manipulandum is a horizontal button that eliminates spurious triggering by water turbulence and problematic response topographies. The button’s design has also been adapted for use by tilapia in an aquacultural food-preference study. The feeder uses a nipple to dispense food pellets reliably under water. In this paper, the apparatus is described in detail. Also discussed are methodological issues related to its design, as well as its usage in a pilot study in which koi learned to discriminate music from silence by using a single manipulandum with food reinforcement.     

DYNAMICS OF CHOICE: RELATIVE RATE AND AMOUNT AFFECT LOCAL PREFERENCE AT THREE DIFFERENT TIME SCALES

To examine extended control over local choice, the present study investigated preference in transition as food‐rate ratio provided by two levers changed across seven components within daily sessions, and food‐amount ratio changed across phases. Phase 1 arranged a food‐amount ratio of 4:1 (i.e., the left lever delivered four pellets and the right lever one pellet); Phase 2 reversed the food‐amount ratio to 1:4, and in Phase 3 the food‐amount ratio was 3:2. At a relatively extended time scale, preference was described well by a linear relation between log response ratio and log rate ratio (the generalized matching law). A small amount of carryover occurred from one rate ratio to the next but disappeared after four food deliveries. Estimates of sensitivity to food‐amount ratio were around 1.0 and were independent of rate ratio. Analysis across food deliveries within rate‐ratio components showed that the effect of a small amount was diminished by the presence of a large amount—that is, when a larger amount was present in the situation (three or four pellets), the value of a small amount (one or two pellets) became paltry. More local analysis of visits to the levers between food deliveries showed that postfood visits following a large amount were disproportionately longer than following a small amount. Continuing food deliveries from the same source tended to make visits less dependent on relative amount, but a discontinuation (i.e., food from the other lever) reinstated dependence on relative amount. Analysis at a still smaller time scale revealed preference pulses following food deliveries that confirmed the tendency toward dependence on absolute amount with continuing deliveries, and toward dependence on relative amount following discontinuations. A mathematical model based on a linear‐operator equation accounts for many of the results. The larger and longer preference following a switch to a larger amount is consistent with the idea that local preference depends on relatively extended variables even on short time scales.     

An inexpensive universal feeder suitable for small numbers of large rations

This report describes a simple universal feeder designed for operant conditioning applications in zoo settings. The apparatus delivers up to six large rations of food. It is portable, easily serviced, and can be constructed in a modest carpentry shop.     

Effect of delay-interval stimuli on delayed symbolic matching to sample in the pigeon

In Experiment 1, food-deprived pigeons received delayed symbolic matching to sample training in a darkened Skinner box. Trials began with the illumination of the grain feeder lamp (no food sample), or illumination of this lamp, accompanied by the raising of the feeder tray (food sample). After a delay of a few seconds, the two side response keys were illuminated, one with red and one with green light, with positions counterbalanced over trials. Pecking the red (green) comparison produced grain reinforcement if the trial had started with food (no food); pecking red after a no-food sample or green after a food sample was not reinforced. Once matching performance was stable, four stimuli were presented during the delay interval, and their effects on matching accuracy were evaluated. Both illumination of the houselight and the center key with white geometric forms decreased matching accuracy, whereas presentation of a tone and vibration of the test chamber did not. In Experiment 2, pecking the red center key was reinforced with food according to a variable interval schedule. The effects of occasional brief presentations of the four stimuli used in the first experiment on ongoing pecking were assessed. The houselight and form disturbed key pecking, but the tone and vibration did not. Thus, stimuli that interfered with delayed matching also interfered with simple operant behavior. Implications of these results for theories of remembering are discussed.     

Control of responding by the location of an auditory stimulus: role of rise time of the stimulus

The control of responding by the location of tone bursts of 0.2- or 50-msec rise time was investigated in three albino rats. The apparatus consisted of an enclosure with two levers, two loudspeakers (in different locations), and a dipper feeder. The animal was exposed to tone bursts from either one or the other of the two speakers, and the speaker through which the tone bursts were delivered on any particular trial alternated in an irregular manner. Responses on one lever were reinforced with food in the presence of tone bursts from one speaker; responses on the second lever were reinforced with food in the presence of tone bursts from the second speaker. Responding came under the control of the location of 4-kHz tone bursts of 0.2-msec rise time within the first session. At this rise time, animals maintained a stable level of correct responding of greater than 95%. When the rise time was increased to 50 msec the percentage of correct responding fell to an average of 80 to 85%. It was concluded that location of an auditory stimulus is a powerful controller of responding in rats and that the degree of control is dependent upon rise time.     

Choice as a dependent measure in autoshaping: sensitivity to frequency and duration of food presentation.

Previous investigations have shown that rate, latency, and percentage of trials with at least one response are somewhat insensitive measures of the strength of autoshaped responding. In the present studies, these measures were contrasted with the allocation of responding during simultaneous choice tests, a measure of response strength frequently used in operant paradigms. In two experiments, nine pigeons were exposed to a forward pairing autoshaping procedure. Training sessions consisted of the successive presentation of three stimuli, each followed by food on either 100%, 50%, or 0% of the trials. Choice testing involved the simultaneous presentation of the three stimuli. In Experiment I, all pigeons consistently directed their initial choice responses and the majority of subsequent responses to the stimulus always followed by food, despite the fact that during training sessions the response rates of most birds were highest in the presence of the stimulus followed by food on 50% of the trials. In Experiment II, rate, latency, and percentage of trials with at least one response did not change appreciably as a function of duration of feeder presentations. However, choice responding was lawfully affected by duration of feeder presentations. These data suggest that choice is perhaps a more sensitive measure of the strength of autoshaped responding than other, more commonly employed, indices.     

Latent inhibition of US signal value.

Three experiments with rats examined the effects of preexposure to an unconditioned stimulus (US; a single food pellet) on the subsequent ability of that US to effectively signal the delivery of three food pellets during a US-US conditioning procedure. In Experiment 1, latent inhibition (LI) rats showed attenuated conditioning, compared to control (C) rats, when a single food pellet, delivered 10 minutes into a session, was followed by three additional pellets. In preexposure, one pellet had been delivered 10 minutes into each session (in group LI), or placed into the magazine at the beginning of each session (in group C). Experiment 2 showed that this effect was evident when the conditions of preexposure matched those of conditioning for group C, and Experiment 3 showed that the difference between groups LI and C was not a product of context conditioning, or latent inhibition to the noise of the feeder in group LI. Implications of these results for theories of latent inhibition are considered.     

Behavior induced by periodic food delivery: The effects of interfood interval

Pigeons were exposed to fixed-time schedules of food presentation ranging from five to 300 seconds. Although consistent, stereotyped response patterns developed during interfood intervals on all schedules, there were distinct differences in the behavior observed on schedules with short, as opposed to long, intervals. During the shorter intervals, responses were performed quite vigorously, a feeder-directed terminal response was observed, and most activities were localized near the feeder. On the longer schedules, no feeder-directed terminal response developed, although the birds were usually near the feeder at the end of intervals. The predominant response involved moving about the chamber, often pacing along one of the walls. Performance during short intervals is accounted for quite well by the antagonistic-motivational state hypothesis suggested by Staddon (1977); however, performance during longer intervals is not. Behavior during interfood intervals may more accurately be classified as reflecting a single (food) motivational state and described simply in terms of Craig's (1918) appetitive behavior.     

A response duration schedule: effects of training, extinction, and deprivation

Rats were trained to hold down a lever for at least 40 consecutive seconds. When the lever had been held down for 40 sec, white noise came on. Releasing the bar in the presence of the noise turned off the noise and operated a feeder that delivered a pellet of food. At the end of training, frequency distributions of response durations peaked at 40 to 41 sec. If as in training, holding down the lever produced white noise at the end of 40 sec, and release of the lever terminated the noise and operated the feeder, but no food delivery occurred, duration distributions and several other measures were initially not very different from when food was delivered. However, if during extinction white noise was never produced by lever holding, and feeder operation did not occur upon lever release, most responses were shorter than 1 sec in duration, some were much longer than 41 sec, and duration distributions did not peak at 40 to 41 sec. When reinforcement was reinstated after extinction, performance quickly returned to pre-extinction measures. Further sessions at different levels of deprivation produced only temporary disruptions in performance.     

A motor-driven feeder for operant training in song birds

Conventional pigeon feeders can make noise, spill food, and injure birds in applications using small song birds as subjects. We developed a motor-driven feeder based on the principle of the piston to address these concerns.     

Reversed effects in closed and open economies

Pigeons received food according to either fixed-interval, fixed-ratio, or random-interval schedules in both closed and open feeding economies. In the closed economy, they were not food deprived, they controlled the amount of food received at each meal, and they had no other source of food. In the open economy, each feeding bout consisted of one feeder cycle, and the pigeons received supplemental feeding as needed to maintain them at 80% of their free-feeding weights. Response rate always increased with larger schedule requirements in the closed economy, but it either decreased steadily or increased and then decreased in the open economy. Initial pauses lengthened with longer fixed intervals or fixed ratios (FR) in the open economy but less so in the closed economy. Responding continued under FR 10,000 schedules in the closed economy, but never survived FR 400 in the open economy. In the open economy, fixed-interval schedules could maintain far more behavior than could either fixed ratios or random intervals. Familiar concepts such as matching and arousal can describe at least some of the behavior in the open economy, but current theory does not apply well to behavior in the closed economy. An explanation of economy-dependent effects might begin with the possibility that the two economies invoke different evolved survival strategies. These strategies influence behavior by means of different mechanisms and laws. The strategy for the closed economy may relate to weight conservation, but that for the open economy may be based on energy conservation.     

Expectancies of reinforcer location and quality as cues for a conditional discrimination in pigeons

Experiment 1 demonstrated that reliably correlating different reinforcer locations (top vs. bottom) with sample stimuli markedly enhanced the performance of White Carneaux pigeons in a spatial conditional discrimination. This differential outcome effect was more evident at longer retention intervals. In Experiment 2, pigeons were given the opportunity to learn about two redundant reinforcer features--location (top vs. bottom) and quality (grain vs. chow). Which reinforcer feature exerted control over choosing depended on task structure. In the congruent task, where pecks to the top key operated the top feeder and pecks to the bottom key operated the bottom feeder, reinforcer location exerted predominant control. In the incongruent task, where pecks to the top key operated the bottom feeder and vice versa, reinforcer quality exerted exclusive control. These results have implications for the nature of reinforcer representations in instrumental learning.