Visual discrimination of horizontal and vertical rectangles by rats on a new discrimination training apparatus

A new visual shape discrimination apparatus for use with rats is described. Rats were trained on a simultaneous discrimination using stereometric shapes, and the reward was milk which was delivered through the middle of the shapes. Animals were trained to discriminate vertical and horizontal rectangles on the apparatus, and it was found that they took as many trials to learn as on a Lashley jumping stand. Because of the speed at which individual trials may be conducted, less actual time is spent on training in this apparatus than in a Lashley jumping stand. Some transfer tests were conducted and indicated that: (1) although the bottom halves of the shapes were more important for rats than the top halves, animals had learned something about the shapes as a whole; (2) animals transferred to discontinuous shapes; (3) they transferred better to larger shapes than to smaller; (4) they had learned both to approach the positive shape, and to avoid the negative shape.     

Preparation for horizontal or vertical dimensions affects the right-left prevalence effect

When stimulus and response simultaneously vary in both horizontal and vertical dimensions, the stimulus-response compatibility effect is often larger for the horizontal dimension. We investigated the role of preparation for each dimension in this right-left prevalence. In Experiment 1, tasks based on horizontal and vertical dimensions were mixed in random order, and the relevant dimension in each trial was cued with a variable cue-target stimulus onset asynchrony (SOA). A right-left prevalence effect was observed only when participants prepared for the upcoming task. Experiment 2 replicated the absence of the prevalence effect for the simultaneous presentation of cue and target using a fixed SOA of 0 msec. In Experiment 3, the right-left prevalence emerged with a 0-msec SOA when participants prepared for e achdimension basedon its frequency. These resultssuggest that participants' internal set can be greater for the horizontal dimension, leading to the right-left prevalence effect.     

Generalization after intradimensional discrimination training in 2-year-old children

Two-year-old children received intradimensional discrimination training at initially distant points on a circle-ellipse continuum. This training often did not produce stimulus control by circle-ellipse differences smaller than the original training values. The lack of control did not reflect capacity limitations, however. Good control was established when the children were given further training at nearer points on the continuum. The data confirm results of earlier research on stimulus generalization, extending them to a developing human subject population.     

Emergent simple discrimination in children: Preference for non-preferred stimuli

Previous research (Smeets, 1991) suggested that when given a new discrimination, children respond on the basis of physical similarity with previously discriminated stimuli. They respond to a stimulus similar to another preferred stimulus (S+ transfer) and respond away from a stimulus similar to another nonpreferred stimulus (S- transfer). When both types of transfer apply to the same stimulus, S+ transfer prevails, S+ Priority Transfer (S+PT). The present study demonstrated that S+PT also occurs when the criterion task consists of two nonpreferred stimuli. When given a choice between two previously nonpreferred stimuli, one similar and one dissimilar to other preferred stimuli, children select the first one. They do not so, however, when a nonpreferred stimulus resembling another preferred stimulus is presented with a new nonpreferred stimulus. These findings suggest that the children's preferences were not based on the physical resemblance with other (non)preferred stimuli but on the functions (S+, S-, S0) of individual stimulus components. A theoretical model is presented that accounts for all experimental data reported in the previous and present study. The model implies that discriminative responding not only results from but also determines the functional properties of individual stimulus elements.     

Direct transfer from a horizontal-vertical discrimination to a brightness discrimination in the rat

Eight rats were trained on a discrimination between horizontal and vertical striations, and subsequently between black and white vertical striations. Subjects originally trained with horizontal positive preferred black to white and subjects trained with vertical positive preferred white to black.

The present note reports briefly on a transfer effect in rats, observed incidentally in an experiment designed for a different purpose. The rats were trained in a jumping stand to discriminate between horizontal and vertical striations, and when training was complete, were tested on a brightness discrimination.     

Preference for and discrimination of videos of conspecific social behavior in mice

We showed mice videos of three conspecific social behaviors, namely sniffing, copulation, and fighting, in pairwise combinations using iPods and evaluated preference as determined by time spent in front of each iPod. Mice preferred the copulation video to the sniffing video, the fighting video to the sniffing video, and the fighting video to the copulation video. In Experiment 1a, we used a single video clip for each social behavior but used multiple video clips for each social behavior in Experiment 2a. Next, we trained mice to discriminate between the fighting and copulation videos using a conditioned-place-preference-like task in which one video was associated with injection of morphine and the other was not. For half of the subjects, the fighting video was associated with morphine injection, and for the other half, the copulation video was associated with morphine injection. After conditioning, the mice stayed longer in the compartment with the morphine-associated video. When tested with still images obtained from the videos, mice stayed longer in the compartment with still images from the video associated with morphine injection (Experiment 1b). When we trained mice with multiple exemplars, the subjects showed generalization of preference for new video clips never shown during conditioning (Experiment 2b). These results demonstrate that mice had a preference among videos of particular behavior patterns and that they could discriminate these videos as visual category. Although relationship between real social behaviors and their videos is still open question, the preference tests suggest that the mice perceived the videos as meaningful stimuli.     

Left of centre: asymmetries for the horizontal vertical line illusion

This study explored the mechanisms that underlie asymmetries for the horizontal vertical illusion (HVI), which deceives length perception, so that a vertical line is perceived as longer than a horizontal line of equivalent length. In Experiment 1, university students (n = 14) made length judgements for vertical and horizontal lines. The vertical line was shifted in eight steps from the far left of the horizontal line (⌊) to the far right (⌋). An HVI was observed for the medial positions (⊥), which diminished towards the lateral positions. The HVI was also stronger when the vertical line was on the left. Because the left/right asymmetry changed as a function of lateral/medial position, the asymmetry within the HVI stimulus is most likely the result of pseudoneglect, which affects judgements of horizontal length. In Experiment 2, participants (n = 15) made judgements for HVI stimuli presented to the left- and right-hemispace and the midline. The HVI was stronger in the left hemispace. Because the asymmetry between the left- and right-hemispaces did not interact with the asymmetry within the stimuli, it was concluded that the asymmetry between hemispatial positions was the result of right hemisphere susceptibility to illusory geometrical effects whereas the asymmetry within the stimulus is related to an object-centred attentional asymmetry. The HVI is affected by asymmetries in length judgements and susceptibility to illusions and may provide interesting insights into attentional disorders in clinical populations, such as neglect.     

Temperature reinforcement for visual discrimination training in baby chicks

A fully automated training apparatus, using thermoregulation as performance incentive, was constructed to train baby chicks on visual discrimination and reversal problems. In the base condition, the S is bathed in cold air in a small training cubicle. Two stimuli are back-projected onto two display windows according to a pseudorandom balanced schedule. A peck at the positive stimulus gives convective as well as radiant heat reward with adjustable temperature and duration. A peck at the negative stimulus merely advances the program to the next trial. Permanent printout records give trial-to-trial information on response choice and latency. Performance data of 64 Ss are reported.     

Error correction in discrimination training for children with autism

Three procedures for correcting errors made during discrimination training were examined: error statement (saying ‘no’), modeling the correct response, and No Feedback. Six children with autism (age 3–7 years) were taught to match words to pictures with each of the three procedures, and the number of trials to mastery was compared across conditions. Results varied across participants. Two participants performed as well with no feedback as they did with an error correction procedure; two acquired skills slightly more quickly with an error correction procedure than with no feedback, but showed no difference between error correction procedures; one did best with error statement; and one did best with modeling. Results indicate that the choice of error correction procedure can have a large effect on rate of skill acquisition but that the optimal procedure may vary across individuals. Copyright © 2006 John Wiley & Sons, Ltd.