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PubMed2005

Seeing the light: illumination as a contextual cue to color choice behavior in bumblebees.

The principal challenge faced by any color vision system is to contend with the inherent ambiguity of stimulus information, which represents the interaction between multiple attributes of the world (e.g., object reflectance and illumination). How natural systems deal with this problem is not known, although traditional hypotheses are predicated on the idea that vision represents object reflectance accurately by discounting early in processing the conflating effects of illumination. Here, we test the merits of this general supposition by confronting bumblebees (Bombus terrestris) with a color discrimination task that can be solved only if information about the illuminant is not discounted but maintained in processing and thus available to higher-order learned behavior. We show that bees correctly use the intensity and chromaticity of illumination as a contextual cue to guide them to different target colors. In fact, we trained bees to choose opposite, rather than most similar, target colors after an illumination change. This performance cannot be explained with a simple color-constancy mechanism that discounts illumination. Further tests show that bees do not use a simple assessment of the overhead illumination, but that they assess the spectral relationships between a floral target and its background. These results demonstrate that bees can be color-constant without discounting the illuminant; that, in fact, they can use information about the illuminant itself as a salient source of information.

Animals↗
PubMed1966

Probabilistically reinforced choice behavior in pigeons.

A single principle, "momentary maximizing", may account for much of a pigeon's steady-state behavior in both probability learning and concurrent variable interval experiments. The principle states that a pigeon tends to choose the alternative that momentarily has the higher probability of reinforcement. A successive discrimination procedure, which produced matching in an earlier experiment, produced here a tendency to maximize if training were adequately extended. Maximizing was produced also by other procedures, in which no reinforcing event was presented on some trials: one procedure did and two did not provide a bird with information about the availability of reinforcement on a key after an unreinforced response on the other key. The latter two procedures were analogous to concurrent variable interval schedules in two respects: the reinforcement probability on one key increased while a bird responded on the other key; and they produced matching. But sequential statistics suggested that matching resulted from momentary maximizing. Depending on the procedure, the tendency to maximize produced different relative frequencies of pecking a key for a fixed relative frequency of reinforcement. Computer simulation of maximizing behavior in several concurrent variable interval schedules produced matching and sequential statistics similar to those produced by a real bird.

Animals↗
PubMed1972

Choice behavior and the accessibility of the reinforcer.

In Experiment 1, matching of relative response rates to relative rates of reinforcement was obtained in concurrent variable-interval schedules when the absolute values of the two concurrent variable-interval schedules varied from 6 sec and 12 sec to 600 sec and 1200 sec. Increases in the duration of the changeover delay, however, produced decreases in the relative response rates and, consequently, some deviation from matching. In Experiment 2, matching of relative response rates to the relative duration of the reinforcer failed to occur when the equal variable-interval schedules arranging access to the two different reinforcer durations (1.5 and 6 sec) were varied in size from concurrent variable-interval 10-sec schedules to concurrent variable-interval 600-sec schedules.

Journal Article↗
PubMed1979

The effect of punishment on free-operant choice behavior in humans.

During Phase I, three female human subjects pressed a button for monetary reinforcement in five variable-interval schedules specifying different frequencies of reinforcement. On alternate days, responding was also punished (by subtracting money) according to a variable-ratio 34 schedule. In the absence of punishment, response rates conformed to Herrnstein's equation for single variable-interval schedules. Punishment suppressed responding at all frequencies of reinforcement. This was reflected in a change in the values of both constants in Herrnstein's equation: the value of the theoretical maximum response-rate parameter was reduced, and the parameter describing the reinforcement frequency corresponding to the half-maximal response rate was elevated. During Phase II, the same five schedules (A) were in operation (without punishment), but in addition, a concurrent variable-interval schedule (B) of standard reinforcement frequency was introduced. On alternate days, responding in Component B was punished according to a variable-ratio 34 schedule. In the absence of punishment, absolute response rates conformed to equations proposed by Herrnstein to describe performance in concurrent schedules; the ratios of the response rates in the two components and the ratios of the times spent in the two components conformed to the Matching Law. When responding in Component B was punished, response rates in Component B were reduced and those in Component A were elevated, these changes being reflected in distortions of the matching relationship.

Journal Article↗
PubMed2006

Affective-motivational influences on feedback-related ERPs in a gambling task.

Theories have proposed that both the stimulus-preceding negativity (SPN) and the medial frontal negativity (MFN) reflect affective/motivational processing. We examined the effect of the motivational impact of feedback stimuli on these ERPs using a simple gambling task, focusing on the influence of prior losses and gains on ERPs and choice behavior. Choices were riskier following large losses than following small losses or large gains. The MFN, however, was larger following larger gains. The SPN preceding the outcome was also larger after a greater gain. Thus, we confirmed that both the MFN and the SPN respond to the motivational properties of the feedback. A dissociation between risk-taking behavior and these ERPs suggests that there could be two monitoring systems: one that leads to riskier responses following losses and a second that leads to heightened expectancy.

Adult↗
PubMed1994

Values influencing neonatal nurses' perceptions and choices.

The purpose of this research was to identify the values influencing the nurses' perception and choice of behavior in a hypothetical clinical situation. The theoretical framework was Rokeach's theory on the nature of human values and value systems. A descriptive study using a mailed survey was conducted on a random sample of 331 members of the National Association of Neonatal Nurses. Data on individual nurse's values, perception of information, and behavioral choices were collected with an investigator-developed questionnaire consisting of a values scale, and an information scale and choice alternatives related to three hypothetical vignettes: a low-birthweight infant, an infant with chromosomal anomalies, and a chronically ill infant. Results of this study indicate that nurses identified a hierarchy of values related to their practice. Information related to infant characteristics was consistently most important; however, in uncertain situations, rules or external protocols had an increased influence on the behavioral choice process. The behavioral choice option with the greatest agreement was different for each situation. A consistently negative correlation between the options within each vignette indicates that nurses have clearly defined choice preferences. Model testing revealed a consistent relationship across the three vignettes between the variable being just and protocol, doing right and infant characteristics, and infant characteristics and the choice options (p < .05).

Adult↗
PubMed2003

Effects of a reward downshift on the consummatory behavior and flower choices of bumblebee foragers.

Insect foragers often exhibit flower constancy, the tendency to visit single flower types rather than sample alternative flowers that provide equal or higher levels of reward. We employed a negative incentive contrast procedure to examine whether a decrease of sucrose concentration in a regularly visited flower type affects bumblebee (Bombus impatiens) consummatory or choice behavior. Subjects were trained to enter a test arena where they foraged on a single, red, artificial flower that contained 140 microl of sucrose solution. Subjects were reinforced with a concentration of either 0.50 or 0.20 sucrose solution in 20 trials and in 12 subsequent test trials subjects were given a choice between a red and yellow flower that each contained 140 microl of 0.20 sucrose solution. Subjects that experienced a downshift of reward showed an abrupt disruption in consumption of sucrose solution from the red flower. These subjects were also significantly more likely to visit the novel yellow flower than subjects that were reinforced with 0.20 sucrose solution in red flowers in all trials. However, the effects of the downshift of reward were transient and appeared to disrupt consummatory behavior more strongly than flower preferences. These results support the idea that bumblebee foragers form expectations of reward in flowers--as is implied by the results of studies of honeybees--and suggest that unrealized expectations of reward may cause foragers to sample alternative flowers or to fly considerable distances in search of particular types of flowers.

Animals↗