Positive Patterning Research Articles

Bimodal Patterning Discrimination in Harnessed Honey Bees

In natural environments, stimuli and events learned by animals usually occur in a combination of more than one sensory modality. An important problem in experimental psychology has been thus to understand how organisms learn about multimodal compounds and how they discriminate this compounds from their unimodal constituents. Here we tested the ability of honey bees to learn bimodal patterning discriminations in which a visual-olfactory compound (AB) should be differentiated from its visual (A) and olfactory (B) elements. We found that harnessed bees trained in classical conditioning of the proboscis extension reflex (PER) are able to solve bimodal positive and negative patterning (NP) tasks. In positive patterning (PP), bees learned to respond significantly more to a bimodal reinforced compound (AB+) than to non-reinforced presentations of single visual (A-) or olfactory (B-) elements. In NP, bees learned to suppress their responses to a non-reinforced compound (AB-) and increase their responses to reinforced presentations of visual (A+) or olfactory (B+) elements alone. We compared the effect of two different inter-trial intervals (ITI) in our conditioning approaches. Whereas an ITI of 8 min allowed solving both PP and NP, only PP could be solved with a shorter ITI of 3 min. In all successful cases of bimodal PP and NP, bees were still able to discriminate between reinforced and non-reinforced stimuli in memory tests performed one hour after conditioning. The analysis of individual performances in PP and NP revealed that different learning strategies emerged in distinct individuals. Both in PP and NP, high levels of generalization were found between elements and compound at the individual level, suggesting a similar difficulty for bees to solve these bimodal patterning tasks. We discuss our results in light of elemental and configural learning theories that may support the strategies adopted by honey bees to solve bimodal PP or NP discriminations.

Summation effects in human learning: evidence from patterning discriminations in goal-tracking.

Participants in two human goal-tracking experiments were simultaneously trained with negative patterning (NP) and positive patterning (PP) discriminations (A+, B+, AB-, C-, D-, CD+). Both elemental and configural models of associative learning predict a PP advantage, such that NP is solved less readily than PP. However, elemental models like the unique cue approach additionally predict responding in AB- trials to be initially stronger than that in A+ and B+ trials due to summation of associative strength. Both experiments revealed a PP advantage and a strong summation effect in AB- trials in the first half of the experiments, irrespective of whether the same US was used for both discriminations (Experiment 1) or two different USs (Experiment 2). We discuss that the correct predictions of the unique cue approach are based on its assumptions of non-normalized and context-independent stimulus processing rather than elemental processing per se.

The transient decline in hippocampal theta power during response inhibition in a positive patterning task.

It is believed that a transient decline in hippocampal theta power is induced by behavioral inhibition during a go/no-go stimulus discrimination task. In a previously reported positive patterning (PP) task, rats learn to lever press when a compound stimulus, both tone and light, is presented and inhibit their lever press when a single stimulus, tone or light, is presented. In this task, rats were required to inhibit their response to the single stimulus in a task where both compound and single stimuli were presented with an overlapping element. Thus, we hypothesized that there would be a transient decline in hippocampal theta power induced by behavioral inhibition to the presence of a single stimuli in the PP task. The result of this study showed that a decline in hippocampal theta power occurred during response inhibition to the presence of a single tone stimulus in the PP task, supporting our hypothesis. However, we did not observe any decline in hippocampal theta power during response inhibition to the presence of a single light stimulus. We found that the error response rate for the tone stimulus was slightly lower than that for light stimulus in the PP task. Thus, we proposed that the decline in hippocampal theta power related to more accurate response inhibition to the stimulus that had an overlapping element.

Comparing positive and negative patterning in human learning

In human causal learning, positive patterning (PP) and negative patterning (NP) discriminations are often acquired at roughly the same rate, whereas PP is learned faster than NP in most experiments with nonhuman animals. One likely reason for this discrepancy is that most causal learning scenarios encourage participants to treat the presentation and omission of the relevant outcome as two events of comparable significance and likelihood. To investigate this, the current experiments compared PP and NP using a predictive learning paradigm based on a mock gambling task. In Experiment 1, one outcome (winning) was made more salient by being less frequent than the alternative outcome (losing). Under these circumstances, PP was learned faster than NP. In Experiment 2, subjects learned two PP and two NP discriminations, one involved win versus no change outcomes, the other involved lose versus no change outcomes. The subjects learned PP faster than NP, but only when discriminating win from no change. We argue that a difference in difficulty between PP and NP relies on a difference in the salience of the outcomes, consistent with the predictions of a relatively simple model of associative learning.

Non-elemental processing in olfactory discrimination tasks needs bilateral input in honeybees

In patterning discriminations, animals have to differentiate a compound stimulus AB from each of its elements A and B. In positive patterning (PP), the compound is reinforced whilst the single elements are non-reinforced. In negative patterning (NP), single elements are reinforced whilst the compound is non-reinforced. Using olfactory conditioning of the proboscis extension response (PER), we asked whether honeybees ( Apis mellifera) can solve these patterning problems when odorants are given unilaterally as well as bilaterally to the antennae. Separating the olfactory input space of bees into two independent zones using plastic walls placed between the antennae, we conditioned bees in PP and NP procedures, with input on one side, on both sides, or in an ambiguous problem where bees had to solve PP on one side and NP on the other side. We found that bees with simultaneous bilateral input solve both patterning tasks efficiently. In contrast, PP but not NP was learned by bees receiving unilateral olfactory input. Bees subjected to the ambiguous NP/PP problem only solved PP. As PP can be solved through mere elemental processes, but NP is critically dependent on the use of non-elemental learning processes, our results suggest that bilateral olfactory input is necessary for non-elemental processing to take place in the bee brain.

No Evidence for Modulation of Evaluative Flavor–Flavor Associations in Humans

In four experiments using a human evaluative flavor–flavor association paradigm, we investigated whether the acquisition of stimulus valence may be subject to Pavlovian modulation or occasion setting. In all studies, subjects (Ss) were exposed to a feature-positive (FP) (XA+/A−) schedule (or a modified version of it), in which flavor A was reinforced by the aversive flavor Tween 20 if and only if it was accompanied by a feature stimulus X. It was expected that Ss would develop an X-dependent dislike for A. In Experiment 1, for half of the Ss a quasi-sequential FP schedule was used, whereby the color of the liquids functioned as X. The other half of the Ss were exposed to a positive-patterning (PP) (XA+/A−/X−) schedule, in which unreinforced color (X−) trials were added to the FP schedule. Both schedules resulted in an unmodulated dislike for flavor A. In Experiment 2, Ss were exposed to a modified FP schedule, in which flavor A was reinforced by Tween 20 when presented with color X, while A was reinforced with positive sugar when presented colorless. Ss again demonstrated an unmodulated dislike for A. Experiment 3, using a sequential FP (X → A+/A−) schedule in which a flavor functioned as X, also resulted in an unmodulated dislike for A. Finally, in Experiment 4, Ss were exposed to the modified FP schedule, in which flavor A was presented with Tween 20 when preceded by flavor X, while A was reinforced with Sugar when not preceded by X. For those Ss liking sugar, no valence shifts were observed, whereas for those not liking sugar, the standard unmodified dislike for A was obtained. Some suggestions are provided with respect to variables which might be related to the absence of modulation.