Delayed search for a concealed imprinted object in the domestic chick

Five-day-old chicks were accustomed to follow an imprinted object (a small red ball with which they had been reared) that was moving slowly in a large arena, until it disappeared behind an opaque screen. In experiments, each chick was initially confined in a transparent cage, from where it could see and track the ball while it moved towards, and then beyond, one of two screens. The screens could be either identical or differ in colour and pattern. Either immediately after the disappearance of the ball, or with a certain delay, the chick was released and allowed to search for its imprinted object behind either screen. The results showed that chicks took into account the directional cue provided by the ball movement and its concealment, up to a delay period of about 180 s, independently of the perceptual characteristics of the two screens. If an opaque partition was positioned in front of the transparent cage immediately after the ball had disappeared, so that, throughout the delay, neither the goal-object nor the two screens were visible, chicks were still capable of remembering and choosing the correct screen, though over a much shorter period of about 60 s. The results suggest that, at least in this precocial bird species, very young chicks can maintain some form of representation of the location where a social partner was last seen, and are also capable of continuously updating this representation so as to take into account successive displacements of the goal-object. Received: 17 January 1998 / Accepted after revision: 29 March 1998     

The establishment of auditory–visual equivalence classes with a go/no-go successive matching-to-sample procedure

The current study evaluated the effectiveness of a go/no-go successive matching-to-sample procedure (S-MTS) to establish auditory–visual equivalence classes with college students. A sample and a comparison were presented, one at a time, in the same location. During training, after an auditory stimulus was presented, a green box appeared in the center of the screen for participants to touch to produce the comparison. Touching the visual comparison that was related to the auditory sample (e.g., A1B1) produced points, while touching or refraining from touching an unrelated comparison (e.g., A1B2) produced no consequences. Following AB/AC training, participants were tested on untrained relations (i.e., BA/CA and BC/CB), as well as tacting and sorting. During BA/CA relations tests, after touching the visual sample, the auditory stimulus was presented along with a white box for participants to respond. During BC/CB relations tests, after touching the visual sample, a visual comparison appeared. Across 2 experiments, all participants met emergence criterion for untrained relations and for sorting. Additionally, 14 out of 24 participants tacted all visual stimuli correctly. Results suggest the auditory–visual S-MTS procedure is an effective alternative to simultaneous MTS for establishing conditional relations and auditory-visual equivalence classes.     

A twin study of spatial and non-spatial delayed response performance in middle age

Delayed alternation and object alternation are classic spatial and non-spatial delayed response tasks. We tested 632 middle-aged male veteran twins on variants of these tasks in order to compare test difficulty, measure their inter-correlation, test order effects, and estimate heritabilities (proportion of observed variance due to genetic influences). Non-spatial alternation (NSA), which may involve greater reliance on processing of subgoals, was significantly more difficult than spatial alternation (SA). Despite their similarities, NSA and SA scores were uncorrelated. NSA performance was worse when administered second; there was no SA order effect. NSA scores were modestly heritable (h(2)=.25; 26); SA was not. There was shared genetic variance between NSA scores and general intellectual ability (r(g)=.55; .67), but this also suggests genetic influences specific to NSA. Compared with findings from small, selected control samples, high "failure" rates in this community-based sample raise concerns about interpretation of brain dysfunction in elderly or patient samples.     

Fixed-interval matching-to-sample: intermatching time and intermatching error runs

Four pigeons were trained on a matching-to-sample task in which reinforcers followed either the first matching response (fixed interval) or the fifth matching response (tandem fixed-interval fixed-ratio) that occurred 80 seconds or longer after the last reinforcement. Relative frequency distributions of the matching-to-sample responses that concluded intermatching times and runs of mismatches (intermatching error runs) were computed for the final matching responses directly followed by grain access and also for the three matching responses immediately preceding the final match. Comparison of these two distributions showed that the fixed-interval schedule arranged for the preferential reinforcement of matches concluding relatively extended intermatching times and runs of mismatches. Differences in matching accuracy and rate during the fixed interval, compared to the tandem fixed-interval fixed-ratio, suggested that reinforcers following matches concluding various intermatching times and runs of mismatches influenced the rate and accuracy of the last few matches before grain access, but did not control rate and accuracy throughout the entire fixed-interval period.     

The role of physical identity of the sample and correct comparison stimulus in matching-to-sample paradigms

Pigeons were trained in a higher-order conditional discrimination paradigm to assess the role of physical identity in a within-subjects design. A line orientation which was super-imposed on all response keys signalled whether a response to the matching color or a response to the nonmatching color was correct. Following training under this paradigm, stimulus control gradients were obtained by varying the angularity of the lines. Orderly gradients of stimulus control were obtained and no bias toward or away from the physically identical comparison stimulus was observed. The data were interpreted as indicating that the pigeons acquired a discrimination for each specific stimulus configuration or a set of specific stimulus-response chains based on compound stimuli in which physical identity played no special role.     

Control of adolescents' arbitrary matching-to-sample by positive and negative stimulus relations.

In Experiment 1, four developmentally delayed adolescents were taught an A-B matching-to-sample task with nonidentical stimuli: given Sample A1, select Comparison B1; given A2, select B2. During nonreinforced test trials, appropriate matching occurred when B stimuli appeared as samples and A stimuli as comparisons, i.e., the sample and comparison functions were symmetrical (B-A matching). During A-B or B-A matching test trials in which familiar samples and correct comparisons were presented along with novel comparisons, the subjects selected the correct comparisons. In tests with familiar samples and both incorrect and novel comparisons, subjects selected the novel comparisons, demonstrating control by both positive ("matching") and negative ("nonmatching") stimulus relations in A-B and B-A arrays. In Experiment 2, 12 developmentally delayed subjects were taught a two-stage arbitrary-matching task (e.g., A-B, C-B matching). Test sessions showed sample-comparison symmetry (e.g., B-A, B-C matching) and derived sample-comparison relations (e.g., A-C, C-A matching) for 11 subjects. These subjects also demonstrated control by positive and negative stimulus relations in the derived relations.     

C1调制效应的理论评述及影响因素

C1成分是对视觉刺激最早做出反应的视皮层诱发电位,C1调制效应是指注意等因素能够影响C1振幅的现象.以往多数研究未观察到注意等因素对C1振幅的影响,仅发现注意等因素对晚于C1的P1与N1等成分存在调制作用,并有研究者据此提出延迟反馈假说.但近期研究提示,注意等因素可能会对C1成分产生影响,提示初级视皮层(V1)可能在视觉信息加工初期直接受注意调制.目前,对C1调制效应的影响因素尚未完全确定,知觉学习、负载等因素的作用尚待考察.未来研究需进一步明确C1调制效应的影响因素及实验条件.