The Differential Outcomes Effect Using Sensory Outcomes in a Many-to-One Matching-to-Sample Task

The present study was designed to evaluate the use of sensory outcomes (visual vs. auditory) using a differential outcomes procedure to facilitate learning in a many-to-one matching-to-sample task. For one group of participants (differential outcomes) each correct stimulus-choice sequence was always followed by a different outcome; whereas for the rest of participants (non-differential outcomes) each correct sequence was followed by the same outcome. Participants trained with differential outcomes showed a faster acquisition and higher overall accuracy than participants trained with non-differential outcomes. The results provide a new extension the differential outcomes effect by using sensory outcomes and many-to-one matching to-sample task; applications of the differential outcomes procedure are discussed.

Training Merino sheep to respond to visual and auditory cues

The feasibility of training sheep to approach a stimulus was investigated in three experimental groups and a control group of fine wool Merino sheep (n = 11 in each group). The experimental groups (n = 11) were trained to approach either a visual (V), auditory (A), or visual + auditory (V+A) stimulus over eight training sessions and were subsequently tested in a T-maze for memory retention on six occasions over a 4-month period. Four testing occasions were spaced at greater than 30 days apart while two were less than 3 days apart. Sheep learned to approach the cues during the training period and the tests indicated that the sheep retained memory of the cues for over 130 days without reinforcement. The controls received no contingency exposure and made no choice in the T-maze test. The proportion of correct stimulus choices (±s.e.m.) in the T-maze averaged over the four longer-spaced testing occasions were V 0.61 (0.06), A 0.50 (0.11), V+A 0.77 (0.04). These differences approached significance (P = 0.058). Sheep trained to the V+A stimulus performed significantly (P < 0.05) better in the T-maze than sheep trained to the A stimulus alone. Comparisons over the shorter-spaced testing durations indicated that the sheep quickly learnt not to approach the stimulus (temporary extinction) when no food reward was available. Individual temperament of the animals was not related to their learning. This study highlights the potential for the use of V and A cues in manipulating the movement of sheep which may be useful for farm management purposes.

On Decoding the Responses of a Population of Neurons from Short Time Windows

The effectiveness of various stimulus identification (decoding) procedures for extracting the information carried by the responses of a population of neurons to a set of repeatedly presented stimuli is studied analytically, in the limit of short time windows. It is shown that in this limit, the entire information content of the responses can sometimes be decoded, and when this is not the case, the lost information is quantified. In particular, the mutual information extracted by taking into account only the most likely stimulus in each trial turns out to be, if not equal, much closer to the true value than that calculated from all the probabilities that each of the possible stimuli in the set was the actual one. The relation between the mutual information extracted by decoding and the percentage of correct stimulus decodings is also derived analytically in the same limit, showing that the metric content index can be estimated reliably from a few cells recorded from brief periods. Computer simulations as well as the activity of real neurons recorded in the primate hippocampus serve to confirm these results and illustrate the utility and limitations of the approach.

Emergent Simple Discrimination in Children: Transfer of Stimulus Control under Non-Reinforced Conditions

Previous research on humans suggests that simple discriminations may emerge if both stimuli, B1 and B2, are compounded with the stimuli of a previously trained discrimination, A1 (S+) and A2 (S-), and responding to the compounds, B1A1 and B2A2, is reinforced. Two questions were addressed. First, do simple discriminations also emerge if (a) only one stimulus, B1, is compounded with a training stimulus, A1 (S+) or A2 (S-); or with both training stimuli, A1 (S+) and A2 (S-); and (b) neither B1 nor B2 is compounded with the training stimuli? Second, do simple discriminations emerge if reinforcement in the presence of the AB compounds is withheld? Normal preschool children served as subjects. The study consisted of six experiments. Transfer occurred in all experiments regardless of whether both test stimuli, one test stimulus, or none of the test stimuli were compounded with the training stimuli under non-reinforced conditions. The results can be described by the following rules: Respond to any stimulus that includes a component of a “correct” stimulus of a previous discrimination. Otherwise, respond away from the stimulus that incorporates a component from an “incorrect” stimulus of a previous discrimination. The implications of data for sensory pre-conditioning and language-based accounts are discussed.

Prompted vs Trial-and-Error Concept Discrimination Learning in Monkeys

8 test-sophisticated rhesus monkeys were tested on concept discrimination problems under conventional trial-and-error (TE) procedures and two forms of prompting, i.e., conditions in which an established cue was temporarily available for solution of the problem. Positive Prompting (PP) included a cue attached to the correct stimulus of the discrimination pair; Negative Prompting (NP), a cue attached to the incorrect stimulus. The data revealed significantly better intraproblem learning following NP than following equivalent amounts of either PP or TE.