Blocking and pseudoblocking: New control experiments with honeybees

Prompted by doubts about the adequacy of the various control procedures long used in research on blocking, we repeated some earlier experiments with honeybees that had given the appearance of forward, concurrent, and backward blocking. The new experiments differed from the earlier experiments only in that the target stimulus was omitted during the training and was encountered for the first time in the test. In the new experiments, just as in the earlier experiments, the blocking groups responded less to the target stimulus than did the control groups. The results show that the effects of the different treatments of nontarget stimuli commonly compared in blocking experiments may generalize to the target stimulus and thus affect responding to that stimulus independently of experience with it. Implications for research on blocking in honeybees and other animals are considered.     

Blocking and pseudoblocking: the reply of Rattus norvegicus to Apis mellifera

Blaser, Couvillon, and Bitterman (2006) presented data obtained with honeybees that in principle challenged all traditional interpretations of blocking. They administered A + followed by either A + or + alone (where + indicates an unconditioned stimulus) and then tested on X. They observed less responding to X when they administered A + than when + alone was administered, a phenomenon they called "pseudoblocking". Here we examined pseudoblocking in a rat fear-conditioning preparation. In Experiment 1, using a control procedure that was similar to our usual blocking control, we obtained conventional blocking but failed to observe pseudoblocking in our analogue to Blaser et al.'s procedure. In Experiment 2, we used Blaser et al.'s control procedure and again failed to observe the pseudoblocking effect with rats when we used the experimental context as an analogue to the honeybee feeder used by Blaser et al. After reviewing their protocol and previously published studies from their laboratory, we hypothesized that the feeder that they treated as a training context probably served as a punctate cue. We also tested this possibility in Experiment 2, using a punctate cue as a surrogate feeder, and were now able to reproduce their pseudoblocking phenomena. Our results are consistent with a simple overshadowing account of pseudoblocking, within the framework of existing theories of associative learning, which is not applicable to the conventional blocking paradigm. Thus, blocking remains a real phenomenon that must be addressed by models of associative learning.     

Blocking and pseudoblocking: The reply of Rattus norvegicus to Apis mellifera

Blaser, Couvillon, and Bitterman (2006) presented data obtained with honeybees that in principle challenged all traditional interpretations of blocking. They administered A + followed by either A + or + alone (where + indicates an unconditioned stimulus) and then tested on X. They observed less responding to X when they administered A + than when + alone was administered, a phenomenon they called “pseudoblocking”. Here we examined pseudoblocking in a rat fear-conditioning preparation. In Experiment 1, using a control procedure that was similar to our usual blocking control, we obtained conventional blocking but failed to observe pseudoblocking in our analogue to Blaser et al.'s procedure. In Experiment 2, we used Blaser et al.'s control procedure and again failed to observe the pseudoblocking effect with rats when we used the experimental context as an analogue to the honeybee feeder used by Blaser et al. After reviewing their protocol and previously published studies from their laboratory, we hypothesized that the feeder that they treated as a training context probably served as a punctate cue. We also tested this possibility in Experiment 2, using a punctate cue as a surrogate feeder, and were now able to reproduce their pseudoblocking phenomena. Our results are consistent with a simple overshadowing account of pseudoblocking, within the framework of existing theories of associative learning, which is not applicable to the conventional blocking paradigm. Thus, blocking remains a real phenomenon that must be addressed by models of associative learning.     

A visual equalization strategy for locomotor control: of honeybees,robots, and humans

Honeybees fly down the center of a corridor by equating the speed of optic flow in the lateral field of the two eyes. This flow-equalization strategy has been successfully implemented in mobile robots to guide behavior in cluttered environments. We investigated whether humans use a similar strategy to steer down a corridor, and determined the relative contributions of equating the speed of flow (.27), the splay angles of base lines (.62), and the visual angles of texture on the left and right walls (.03) to steering behavior. A generalized equalization strategy based on the weighted linear combination of these variables closely models human behavior, providing robust visual control.     

Correspondence as conditional stimulus control: insights from experiments with pigeons.

Correspondence between saying and doing, typically studied in young children and individuals with developmental disabilities, was examined as an instance of conditional stimulus control. In Experiment 1, 3 pigeons were exposed to a two‐component repeated‐trials procedure. In the first—sample or say—component, two response keys transilluminated by different colored lights were presented and the pigeon pecked one of the keys. After 1 s of darkness in the chamber, the second—choice or do—component was presented, in which the two keys again were transilluminated, one by the color selected in the first component and the second by another color. Selecting the color that matched that selected in the say component resulted in access to food. Selecting the other color produced a blackout of the chamber. After an intertrial interval (ITI), the next say component was programmed, and the procedure was repeated. Correspondence remained at chance levels through several manipulations of ITI duration and sample response requirement. When a correction procedure was added such that only the originally selected sample stimulus was re‐presented until a correct choice response occurred, reliable correspondence developed in 2 pigeons. This correspondence was eliminated by making reinforcement independent of correspondence and subsequently was reestablished when reinforcement again depended on correspondence. In Experiment 2, 3 other pigeons rapidly acquired correspondence under the final procedure used in Experiment 1. Increasing the time interval between the say and do components diminished correspondence. The results of the two experiments suggest how correspondence may be considered an instance of conditional stimulus control and that it is possible to construct a homologue of human say‐do correspondence with pigeons.     

Visualization of multiple influences on ocellar flight control in giant honeybees with the data-mining tool Viscovery SOMine

Viscovery SOMine is a software tool for advanced analysis and monitoring of numerical data sets. It was developed for professional use in business, industry, and science and to support dependency analysis, deviation detection, unsupervised clustering, nonlinear regression, data association, pattern recognition, and animated monitoring. Based on the concept of self-organizing maps (SOMs), it employs a robust variant of unsupervised neural networks—namely, Kohonen’s Batch-SOM, which is further enhanced with a new scaling technique for speeding up the learning process. This tool provides a powerful means by which to analyze complex data sets without prior statistical knowledge. The data representation contained in the trained SOM is systematically converted to be used in a spectrum of visualization techniques, such as evaluating dependencies between components, investigating geometric properties of the data distribution, searching for clusters, or monitoring new data. We have used this software tool to analyze and visualize multiple influences of the ocellar system on free-flight behavior in giant honeybees. Occlusion of ocelli will affect orienting reactivities in relation to flight target, level of disturbance, and position of the bee in the flight chamber; it will induce phototaxis and make orienting imprecise and dependent on motivational settings. Ocelli permit the adjustment of orienting strategies to environmental demands by enforcing abilities such as centering or flight kinetics and by providing independent control of posture and flight course.     

Maze navigation by honeybees: learning path regularity

We investigated the ability of honeybees to learn mazes of four types: constant-turn mazes, in which the appropriate turn is always in the same direction in each decision chamber; zig-zag mazes, in which the appropriate turn is alternately left and right in successive decision chambers; irregular mazes, in which there is no readily apparent pattern to the turns; and variable irregular mazes, in which the bees were trained to learn several irregular mazes simultaneously. The bees were able to learn to navigate all four types of maze. Performance was best in the constant-turn mazes, somewhat poorer in the zig-zag mazes, poorer still in the irregular mazes, and poorest in the variable irregular mazes. These results demonstrate that bees do not navigate such mazes simply by memorizing the entire sequence of appropriate turns. Rather, performance in the various configurations depends on the existence of regularity in the structure of the maze and on the ease with which this regularity is recognized and learned.     

From vision to action: experiments and models of steering control during driving

Experienced drivers performed simple steering maneuvers in the absence of continuous visual input. Experiments conducted in a driving simulator assessed drivers' performance of lane corrections during brief visual occlusion and examined the visual cues that guide steering. The dependence of steering behavior on heading, speed, and lateral position at the start of the maneuver was measured. Drivers adjusted steering amplitude with heading and performed the maneuver more rapidly at higher speeds. These dependencies were unaffected by a 1.5-s visual occlusion at the start of the maneuver. Longer occlusions resulted in severe performance degradation. Two steering control models were developed to account for these findings. In the 1st, steering actions were coupled to perceptual variables such as lateral position and heading. In the 2nd, drivers pursued a virtual target in the scene. Both models yielded behavior that closely matches that of human drivers.     

PSYCHOBASIC: A BASIC dialect for the control of psychological experiments with the Commodore-64 and DELA interfacing

A modified version of BASIC for the control of psychological experiments is presented. PSYCHOBASIC runs on Commodore-64 computers with DELA interfacing, and it is based on Commodore BASIC. New commands control digital and analog input and output, centisecond timers, and counters. A control panel, which is displayed on the screen at all times, gives the status of many PSYCHOBASIC components. The interpreted nature of PSYCHOBASIC, as well as the control panel, makes the system easy to learn and use. The PSYCHOBASIC system is less expensive than equivalent systems for IBM-PC computers. A sample PSYCHOBASIC program is given.     

Imagination and insight: a new acount of the content of thought experiments

This paper motivates, explains, and defends a new account of the content of thought experiments. I begin by briefly surveying and critiquing three influential accounts of thought experiments: James Robert Brown’s Platonist account, John Norton’s deflationist account that treats them as picturesque arguments, and a cluster of views that I group together as mental model accounts. I use this analysis to motivate a set of six desiderata for a new approach. I propose that we treat thought experiments primarily as aesthetic objects, specifically fictions, and then use this analysis to characterize their content and ultimately assess their epistemic success. Taking my starting point from Kendall Walton’s account of representation (Mimesis as make-believe, Harvard University Press, Cambridge, 1990), I argue that the best way to understand the content of thought experiments is to treat them as props for imagining fictional worlds. Ultimately, I maintain that, in terms of their form and content, thought experiments share more with literary fictions and pictorial representations than with either argumentation or observations of the Platonic realm. Moreover, while they inspire imaginings, thought experiments themselves are not mental kinds. My approach redirects attention towards what fixes the content of any given thought experiment and scrutinizes the assumptions, cognitive capacities and conventions that generate them. This view helps to explain what seems plausible about Brown’s, Norton’s, and the mental modelers’ views.     

Configural olfactory learning in honeybees: negative and positive patterning discrimination

In an appetitive context, honeybees (Apis mellifera) learn to associate odors with a reward of sucrose solution. If an odor is presented immediately before the sucrose, an elemental association is formed that enables the odor to release the proboscis extension response (PER). Olfactory conditioning of PER was used to study whether, beyond elemental associations, honeybees are able to process configural associations. Bees were trained in a positive and anegative patterning discrimination problem. In the first problem, single odorants were nonreinforced whereas the compound was reinforced. In the second problem, single odorants were reinforced whereas the compound was nonreinforced. We studied whether bees can solve these problems and whether the ratio between the number of presentations of the reinforced stimuli and the number of presentations of the nonreinforced stimuli affects discrimination. Honeybees differentiated reinforced and nonreinforced stimuli in positive and negative patterning discriminations. They thus can process configural associations. The variation of the ratio of reinforced to nonreinforced stimuli modulated the amount of differentiation. The assignment of singular codes to complex odor blends could be implemented at the neural level: When bees are stimulated with odor mixtures, the activation patterns evoked at the primary olfactory neuropile, the antennal lobe, may be combinations of the single odorant responses that are not necessarily fully additive.     

Blocking in successive differential conditioning: Prior acquisition of control by internal cues blocks the acquisition of control by brightness

In each of four experiments the acquisition of discriminative stimulus control by brightness cues (black vs white runway) in a successive go/no-go instrumental discrimination was blocked in groups given prior discrimination training with internal (reward-produced and intertrial interval-related) cues as relevant discriminanda and brightness cues irrelevant. The blocking effects obtained here in instrumental conditioning were substantial and in most cases complete. Blocking occurred whether brightness in Phase I varied across trials but was uncorrelated with reinforcement (varied-irrelevant, V-I, condition) or whether all Phase 1 trials occurred to a single value on the brightness dimension (constant-irrelevant, C-I, condition) which then served as a redundant S+ cue in Phase 2 while the previously unexperienced brightness cue was added to the S- stimulus compound, or vice versa. Blocking in the V-I condition was shown not to be due simply to nondifferential reinforcement of brightness in Phase 1, but to depend on the prior acquisition of discriminative stimulus control by internal cues. As in Pavlovian conditioning, blocking here was an increasing function of amount of prior conditioning to the blocking stimulus. The results encourage the prospect that the procedures used here can be developed into a viable instrumental conditioning companion to the Pavlovian procedures now used almost exclusively to study blocking.     

Top-down gain control in the auditory system: evidence from identification and discrimination experiments

The influence of intensity range in auditory identification and intensity discrimination experiments is well documented and is usually attributed to nonsensory factors. Recent studies, however, have suggested that the stimulus range effect might be sensory in origin. To test this notion, in one set of experiments, we had listeners identify the individual tones in a set. One baseline condition consisted of identifying four 1-kHz, low-intensity tones; the other consisted of identifying four 1-kHz, high-intensity tones. In the experimental conditions, these baseline tone sets were augmented by adding a fifth tone at either 1 or 5 kHz. Added 5-kHz tones had little effect on identification accuracy for the four baseline tones. When an added 1-kHz tone differed substantially in intensity from the four baseline tones, it adversely affected performance, with the addition of a high-intensity tone to a set of low-intensity tones having a more deleterious effect than the addition of a low-intensity tone to a set of high-intensity tones. These and further results, obtained in an exploration of this asymmetrical range effect in a third identification experiment and in two intensity-discrimination experiments, were consistent with the notion of a nonlinear amplifier under top-down control whose functions include protection against sensory overload from loud sounds. The identification data were well described by a signal-detection model using equal-variance Laplace distributions instead of the usual Gaussian distributions.     

Inhibitory neurotransmission and olfactory memory in honeybees

In insects, gamma-aminobutyric acid (GABA) and glutamate mediate fast inhibitory neurotransmission through ligand-gated chloride channel receptors. Both GABA and glutamate have been identified in the olfactory circuit of the honeybee. Here we investigated the role of inhibitory transmission mediated by GABA and glutamate-gated chloride channels (GluCls) in olfactory learning and memory in honeybees. We combined olfactory conditioning with injection of ivermectin, an agonist of GluCl receptors. We also injected a blocker of glutamate transporters (L-trans-PDC) or a GABA analog (TACA). We measured acquisition and retention 1, 24 and 48 h after the last acquisition trial. A low dose of ivermectin (0.01 ng/bee) impaired long-term olfactory memory (48 h) while a higher dose (0.05 ng/bee) had no effect. Double injections of ivermectin and L-trans-PDC or TACA had different effects on memory retention, depending on the doses and agents combined. When the low dose of ivermectin was injected after Ringer, long-term memory was again impaired (48 h). Such an effect was rescued by injection of both TACA and L-trans-PDC. A combination of the higher dose of ivermectin and TACA decreased retention at 48 h. We interpret these results as reflecting the involvement of both GluCl and GABA receptors in the impairment of olfactory long-term memory induced by ivermectin. These results illustrate the diversity of inhibitory transmission and its implication in long-term olfactory memory in honeybees.     

Overshadowing and Blocking as Acquisition Deficits: No Recovery After Extinction of Overshadowing or Blocking Cues

The effects of extinction of the blocking or overshadowing stimulus on conditioned responding controlled by the blocked or overshadowed stimulus were examined in seven appetitive conditioning experiments with rats. The experiments differed in their designs, stimuli used, the amounts of conditioning and extinction training, and the levels of conditioned responding produced. In all cases, conditioned responding to the blocked or overshadowed cue was either unaffected or reduced by extinction of the blocking or overshadowing cue. These data are consistent with accounts of overshadowing and blocking that attribute those phenomena to acquisition deficits, rather than to retrieval failures.     

A high-level language for control of psychology experiments

A language for controlling learning, memory, and perception experiments is described. The language features the capability of manipulating large amounts of alphanumeric information with ease. A small, but powerful, command set uses the psychologists’, rather than the programmers’, logic and jargon.     

Blocking the development of stimulus control when stimuli indicate periods of nonreinforcement

To learn whether prior discrimination training based on one stimulus would block learning about a subsequently added stimulus, rats were first trained to press a bar on a variable-interval schedule of food reinforcement. Occasional stimuli were presented during which no reinforcement was available. Responding became suppressed in the presence of these stimuli. Stimuli could be noise, light, or a compound of noise plus light. A group trained with noise in Phase 1, then trained with the compound in Phase 2, showed less suppression to light in a subsequent test than a group that had the same compound training in Phase 2 but only variable-interval training in Phase 1. This showed that prior training with noise blocked the development of control by light during compound training. Two further groups showed that noise training following compound training did not have the same effect on control by light.