Rats with dorsal hippocampal lesions do react to new stimuli but not to spatial changes of known stimuli

The effect of visual distracting stimuli upon the straight alleyway performance of dorsal hippocampectomized Wistar rats was investigated. In comparison with control animals it was observed that dorsal hippocampectomized animals (1) ambulated more during the preexposure phase, (2) acquired at the same rate a running response for food (training phase), (3) reacted similarly to a new visual stimulus (black cards) presented in a sector of the alleyway, and (4) habituated to successive presentations of that stimulus in the same place. (5) However, dorsal hippocampectomized rats did not react, unlike the controls, to the presentation of the same stimulus in another place of the alleyway but (6) reacted to the visual pattern change of the stimulus (now black/white check cards) in the same place. These results indicate that under certain experimental conditions, hippocampus-lesioned animals are capable of interrupting a running response for food in order to explore a new conspicuously located stimulus, habituate to repeated presentations of that stimulus, and to react to a new pattern of visual stimulation. They suggest that hippocampectomized rats do not lose the capacity to react to a new stimulus; the disruption seems to be related to the spatial context of stimulus presentation, supporting a spatial mapping hypothesis of hippocampal function.     

How bumblebees first find flowers: Habituation of visual pattern preferences, spontaneous recovery, and dishabituation

Two experiments examined the exploratory behaviour of flower-naïve bumblebees. Bees were tested four times in a 12-arm radial arm maze in which they never received reward. Patterned and unpatterned stimuli were presented at the end of each corridor and the choices of the bees were recorded. We examined the effects of two variables, time and the presentation of a new stimulus, on habituation to a visual pattern. In Experiment 1, once bees had shown an unlearned preference for a pattern, and the preference had habituated, a response decrement was maintained after a confinement in the colony of two hours. After a 24 h confinement, however, the pattern preference was restored, i.e., spontaneous recovery was observed. In Experiment 2, the presentation of a new stimulus triggered renewed responding to the old pattern to which the bees had habituated, i.e., dishabituation was observed. Habituation to visual patterns is modulated by time and by exposure to new stimuli so that exploration in the face of failure to find food persists and unrewarding visual patterns are not eliminated for long as possible sources of food.     

Are conditioned stimuli determinants of oriented exploratory behavior in the rat?

To test Bindra and Palfai's hypothesis about enhancing and inhibitory motivational effects of a conditioned stimulus on exploratory behavior, rats in a first experiment were submitted to pairings of a tone with (a) water, (b) intermittent deliveries of water after a period of constant pairing. In a control condition, the tone was presented alone. The tone was subsequently presented during oriented exploration of a novel stimulus, in the conditioning context. There was no difference in exploratory performance between conditions. In a second experiment with another kind of stimulus change and a larger number of training trials, exploration did not increase when occurring during CS presentation. The lack of facilitation which is possibly the product of competition between exploration and magazine-directed responses, can also be interpreted as indicating that the effects of a conditioned stimulus are reinforcer specific and that the diffuse activity it generates in a situation different from the training one is not equivalent, as concerns the processes involved, to oriented exploratory behavior.     

Effects of multimodal presentation and stimulus familiarity on auditory and visual processing

Two experiments examined the effects of multimodal presentation and stimulus familiarity on auditory and visual processing. In Experiment 1, 10-month-olds were habituated to either an auditory stimulus, a visual stimulus, or an auditory-visual multimodal stimulus. Processing time was assessed during the habituation phase, and discrimination of auditory and visual stimuli was assessed during a subsequent testing phase. In Experiment 2, the familiarity of the auditory or visual stimulus was systematically manipulated by prefamiliarizing infants to either the auditory or visual stimulus prior to the experiment proper. With the exception of the prefamiliarized auditory condition in Experiment 2, infants in the multimodal conditions failed to increase looking when the visual component changed at test. This finding is noteworthy given that infants discriminated the same visual stimuli when presented unimodally, and there was no evidence that multimodal presentation attenuated auditory processing. Possible factors underlying these effects are discussed.     

Interactive learning in the paradise fish (Macropodus opercularis): an ethological interpretation of the second-order conditioning paradigm

This study was aimed at the examination of ‘mental construction’ in paradise fish by interactive learning, which is suggested as an alternative hypothesis for backward or second-order conditioning. Avoidance of goldfish was established in paradise fish by presenting a harmless goldfish (a novel stimulus) after an aversive event (mild electric shocks) in the dark compartment of a shuttle tank. It was found that this avoidance depended on context pre-exposure. Experiment 1 was designed to study the effect of mild shocks on shuttling activity in a familiar context. Experiment 2 aimed at establishing fear-conditioning to the goldfish in a higher-order conditioning paradigm. In the course of training, unpaired stimuli were presented in the dark compartment of the shuttle tank in such a manner that the presentation of mild shocks (20 mA) preceded the encounter with a harmless fish (goldfish). Experiment 3 demonstrated the role of context pre-exposure in interactive learning. Results indicate that (1) while 60 mA shocks resulted in avoidance of the dark compartment, the 20 mA mild shocks affected exploratory behaviour; (2) after pre-exposure to the training environment, paradise fish avoided the dark compartment containing goldfish provided that subjects had previously encountered mild, explorative shocks there; (3) this conditioned fear, a ‘mental construction’ of a potential danger, was proved to be transferable to another context and was consequently aimed specifically at the goldfish, a living being, rather than the training context; (4) the pre-exposure to the shuttle tank was an important part of this training procedure, that is, only subjects habituated to the shuttle tank avoided the goldfish. Results are discussed in the framework of the Interactive Learning Hypothesis, which has been developed as an ethological approach to a higher-order conditioning paradigm. Received: 15 January 1999 / Accepted after revision: 18 August 1999     

Stimulus probability and same-different classification

Three experiments investigated the effect of stimulus probability on same-different classification time. In Experiments I and II, subjects made same responses on the basis of name matches of simultaneously presented letters. Half of the same trials involved letters that were also physically identical. Experiment I showed that the presentation probability of specific letters affected name matches and different responses, but not physical matches. Experiment II varied stimulus contrast as well as probability. Contrast had a main effect but did not interact with probability at any level of processing. In Experiment III, subjects were switched to the physical level of processing. Stimuli that now had the same name but differed in case were called different. In this condition, the probability effects obs(irved in Experiment II disappeared. These results are interpreted as demonstrating that stimulus probability has its effect during the process that derives the name of the stimulus from the visual representation. This process takes place before the name comparison is made, and the name comparison process precedes the determination of the different response.     

Fine orientation discrimination and shape constancy in young infants

The present study aimed to investigate simultaneously fine orientation discrimination and shape constancy in young infants. The design employed two variants of the habituation paradigm. Infants in one group were habituated to a single orientation (5 or 15 degrees) of a single stimulus presented repeatedly, and they were then tested with the complementary orientation (15 or 5 degrees). Infants in a second group were habituated to several orientations (5, 10, and 15 degrees) of the same stimulus, and they were then tested with a familiar orientation of the stimulus, with two novel orientations of the same stimulus, and with a new stimulus. Between-groups comparison showed that infants habituated more efficiently to re-presentations of a single orientation than to multiple orientations of the same stimulus, providing evidence of fine orientation discrimination; posthabituation comparison within the single-orientation group confirmed that infants discriminated small orientation changes. Posthabituation comparison within the multiple-orientation group showed that infants generalized over novel orientation changes of the familiar stimulus though they discriminated change to a novel stimulus. Cumulatively, the results of this study demonstrate that under one set of conditions young infants show sensitivity to relatively fine variations in pattern orientation, but that under a different set of conditions young infants give evidence of shape constancy with the same patterns.     

Rate changes after unscheduled omission and presentation of reinforcement

Changes in response rate similar to frustration effects were studied in a two-lever situation. Responding on one lever on a fixed-interval schedule produced access to water for 5 sec and an exteroceptive stimulus. In the presence of this stimulus, responding on another lever on a fixed-interval schedule produced access to water for 5 sec and terminated the stimulus. Occasional omission of a previously scheduled reinforcer after responding on the first lever resulted consistently in increases in rate on the second lever during the immediately succeeding interval. In another procedure, occasional presentation of a previously unscheduled reinforcer after responding on the first lever resulted consistently in decreases in rate on the second lever during the immediately succeeding interval. Changes occurred after the first omissions or presentations and were about the same in magnitude as the procedure continued over several sessions. Typically, an increase or decrease in rate was maintained throughout an entire 100-sec interval. Changes in rate on the second lever of approximately the same magnitude also occurred when rate on the first lever was near-zero under a schedule that differentially reinforced behavior other than lever pressing.     

Elicitation and Inhibition of Competitive Fighting in Food Deprived Mice

Habituation as an index of the intrasensory and intersensory integration of form was investigated in nine-year-old children. In Habituation Period One, Ss were habituated to either a visual or a haptic 14″-perimeter standard stimulus. During Habituation Period Two, groups were subdivided and presented with one of the following stimuli: (a) 14″ visual, (b) 16″ visual, (c) 14″ haptic, or (d) 16″ haptic. The dependent variables were GSR frequency and amplitude, visual fixation time, and touching time. Subjects required more trials to habituate to the different stimulus presented in Habituation Period Two than Ss who received repeated presentations of the same stimulus. GSR frequency and amplitude habituated more consistently than did fixation and touching response measures. The results supported the use of the habituation paradigm for the study of intersensory and intrasensory integration, as well as providing support for extending Sokolov's theory to intersensory functions.     

like and cross modality recognition in subnormal children

The ability of mentally subnormal children to recognize previously presented visual or verbal stimuli was compared. In “like-modality” procedures they had to recognize words or pictures in the modality in which they had originally been presented. In “cross-modality” procedures the stimulus they had to recognize was in the opposite modality from that which had been used for the first presentation.

In every recognition test the items had to be recognized from among an equal number of novel stimuli. Cross-modality procedures resulted in higher recognition scores. The hypothesis is advanced that this could be accounted for by the necessary translation from one type of sensory image to another in the cross-modality trials, which might minimize over-generalization.     

Goal attribution to schematic animals: do 6‐month‐olds perceive biological motion as animate?

Infants are sensitive to biological motion, but do they recognize it as animate? As a first step towards answering this question, two experiments investigated whether 6‐month‐olds selectively attribute goals to shapes moving like animals. We habituated infants to a square moving towards one of two targets. When target locations were switched, infants reacted more to movement towards a new goal than a new location – but only if the square moved non‐rigidly and rhythmically, in a schematic version of bio‐mechanical movement older observers describe as animal‐like ( Michotte, 1963 ). Goal attribution was specific to schematic animal motion: It did not occur if the square moved rigidly with the same rhythm as the animate stimulus, or if the square had the same amount of non‐rigid deformation, but in an inanimate configuration. The data would seem to show that perception of schematic animal motion is linked to a system for psychological reasoning from infancy. This in turn suggests that 6‐month‐olds may already interpret biological motion as animate.     

Perceptual-motor processing of phonetic features in speech

Some reaction time experiments are reported on the relation between the perception and production of phonetic features in speech. Subjects had to produce spoken consonant-vowel syllables rapidly in response to other consonant-vowel stimulus syllables. The stimulus syllables were presented auditorily in one condition and visually in another. Reaction time was measured as a function of the phonetic features shared by the consonants of the stimulus and response syllables. Responses to auditory stimulus syllables were faster when the response syllables started with consonants that had the same voicing feature as those of the stimulus syllables. A shared place-of-articulation feature did not affect the speed of responses to auditory stimulus syllables, even though the place feature was highly salient. For visual stimulus syllables, performance was independent of whether the consonants of the response syllables had the same voicing, same place of articulation, or no shared features. This pattern of results occurred in cases where the syllables contained stop consonants and where they contained fricatives. It held for natural auditory stimuli as well as artificially synthesized ones. The overall data reveal a close relation between the perception and production of voicing features in speech. It does not appear that such a relation exists between perceiving and producing places of articulation. The experiments are relevant to the motor theory of speech perception and to other models of perceptual-motor interactions.     

大脑两半球与整体和局部性质的选择性加工

研究大脑两半球在加工整体和局部性质中的优势以及两半球能否同时分别选择两个复合刺激的整体和局部性质。实验中把一个复合字母随机呈现在左视野或右视野,或者把两个复合字母同时分别呈现在左视野和右视野。实验一发现,在单侧呈现条件下,被试检测左右视野的整体或局部靶目标的反应时没有显著差别,但在双侧同时呈现条件下,检测右视野局部靶目标比检测左视野局部靶目标时的反应时短。实验二要求被试检测同时呈现在左右视野的整体或局部靶目标,发现当两个视野的靶目标处于同一水平时(整体或局部)反应时较短,两个视野的靶目标处于不同水平时(一侧处于整体水平而另一侧处于局部水平)反应时较长。这些结果提示,当两个复合刺激同时呈现在左右视野时,大脑左半球在选择性加工局部性质时具有优势;左右两半球更容易选择两个复合刺激同一个水平的性质,分别选择两个复合刺激不同水平的性质比较困难。     

Context specificity of conditioning and latent inhibition: Evidence for a dissociation of latent inhibition and associative interference

Conditioning may generalize from one context to another when latent inhibition (the effect on subsequent conditioning of prior unreinforced exposure to the stimulus) does not. Experiment 1 studied conditioned approach and licking by rats to a stimulus paired with the delivery of water and confirmed that latent inhibition could be abolished by a change of context, while prior aversive conditioning to the stimulus, produced by pairing it with mild shock, interfered with the acquisition of conditioned approach and licking regardless of this change of context. Thus even when conditioning and latent inhibition were measured in the same way, the former generalized across contexts, and the latter did not. Experiment 2 showed that the effects not only of unreinforced exposure to a stimulus but also of presentation of the stimulus uncorrelated with the delivery of water were confined to the context in which they occurred. Thus the generalization of conditioning from one context to another and the failure of latent inhibition to generalize cannot be attributed to the occurrence of rein-forcers during conditioning and their absence in latent inhibition. This conclusion was confirmed in Experiment 3, where animals received both aversive conditioning trials and unreinforced presentations of other stimuli in the treatment phase of the experiment, but were then conditioned to one of these stimuli paired with water. Once again, the effects of aversive conditioning transferred perfectly from one context to another, while those of unreinforced presentations did not. Latent inhibition, these results suggest, is not easily explained by supposing that animals associate an unreinforced stimulus with zero consequences and have to unlearn this association when the stimulus is then paired with a reinforcer.     

非预想刺激的运动速率对无意视盲的影响

无意视盲是指由于对某些事物的专注而导致的眼前对象被忽视的现象。它受到诸如非预想刺激的位置、大小、颜色; 非预想刺激与注意刺激之间的关系; 被试的年龄、专业知识、加工能力等诸多因素的影响。本文通过改进的MR范式考察了“等时”和“等距”条件下非预想刺激的运动速率对无意视盲的影响。实验结果显示: (1)非预想刺激的运动速率和其呈现时间对无意视盲的比率有显著影响; (2)在一定的呈现时间范围内, 视盲率随运动速率的升高而降低, 但当维持相等的运动距离时, 视盲率没有显著变化; (3)当呈现时间超出一定范围时, 运动速率对无意视盲的影响急剧减小, 即呈现时间制约着运动速率对无意视盲的影响, 两者间呈倒U型曲线关系。文末就实验结果进行了详细分析和讨论。     

Visual stimulus input, saccadic suppression, and detection of information from the postsaccade scene

Tachistoscopic presentation of saccadic stimulus sequences to fixating subjects produced saccadic suppression curves only when the pre- and postsaccade fixation fields were structured. Displacement in the sense either of movement of the intrasaccade display or of change from pre- to postsaccade fixation field was not required. Variation of intrasaccade displays from contours moving at saccadic rates to a stationary gray field had no effect. When one structured field immediately followed another, the change of sensitivity mimicked suppression, but an interposed grayout magnified the loss and therefore probably reduced carryover from the first fixation field. Interposed grayout also delayed recovery but reduced the latency of detection of information from the postfield, so that it appears to have reduced stimulus overload from the sudden presentation of the second field.     

Testing for inhibitory stimulus control with S- superimposed on S+

Pigeons learned a successive discrimination between a positive stimulus (red) correlated with a variable-interval 1-min reinforcement schedule and a negative stimulus (vertical line) correlated with either a variable-interval 5-min schedule or extinction. Transfer tests measured the rate of responding to the positive stimulus alone, to various orientations of the negative stimulus, and to the same line orientations superimposed on the positive stimulus. Although there were no gradients with minima at the training value for the negative stimulus dimension, the addition of the negative stimulus dimension to the positive stimulus always resulted in a lower response rate than that for the positive stimulus alone. The results demonstrate that an operational definition of inhibitory stimulus control that requires increased responding to stimuli more distant from a negative stimulus (along some dimension) is not always consistent with a definition that requires the suppression of responding in the presence of one stimulus, the positive stimulus, by the simultaneous presentation of another, the negative stimulus.     

At first glance, transparency enhances assimilation

We investigated the role of transparency, perceptual grouping, and presentation time on perceived lightness. Both transparency and perceptual grouping have been found to result in assimilation effects, but only for ambiguous stimulus displays and with specific attentional instructions. By varying the presentation times of displays with two partly overlapping transparent E-shaped objects, we measured assimilation in unambiguous stimulus displays and without specific attentional instructions. The task was to judge which of two simultaneously presented E-shaped objects was darker. With unrestrained presentation times, if a transparency interpretation was possible, assimilation was not found. Inhibiting a transparency interpretation by occluding the local junctions between the two E-shaped objects, did lead to assimilation. With short presentation times, if a transparency interpretation was possible, assimilation was now also found. Thus, we conclude that, although transparency appears to enhance assimilation, with unambiguous stimulus displays and without specific attentional instructions, perceptual grouping is more important for assimilation to occur.     

The effects of preexposure to a learning apparatus

ICR mice were given exposure to a one-way shuttle apparatus until locomotor activity had been habituated. When compared with nonexposed animals, the exposed animals displayed superior shuttle avoidance learning. Animals exposed to both the apparatus and the CS did not differ from the nonexposed group. It was concluded that preexposure to the learning apparatus facilitated acquisition, while preexposure to the apparatus in the presence of the CS did not. The relationship between this effect and habituation was considered.