Stimulus generalization.

An elaboration and criticism of the immense literature (127 titles) covering the subject. The definition is: when a response, previously trained to be elicited, can also be elicited by test stimuli similar, though with a gradient physically determined. Of course, the response might then also be generalized. Stimulations mentioned are tactual space, light intensity, time, pitch in hearing, loudness, seen angles and other drawings, "drive" intensified by drugs, etc. Theories distinguish irradiation in the cortex and irradiation over neural pathways. Historically, neural science does not seem to be quite ripe for theorizing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus generalization and schizophrenia.

Paranoid and nonparanoid schizophrenics, on and off drugs, were compared with medical inpatients for stimulus-generalization responsivity. The stimuli were lines differing in length, and the response alternatives differed in amplitude. There were no significant differences in gradients of stimulus generalization among the groups. This finding opposes Mednick's original anxiety-drive theory of schizophrenia, especially his assumption that schizophrenics overgeneralize. The finding does not oppose Mednick's amended theory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus generalization among schizophrenics and normal subjects.

Compared schizophrenic and normal groups on a stimulus generalization (SG) task and attempted to explore whether differences in SG among schizophrenics were related to the type of reinforcement applied during acquisition or to diagnostic subtype. 48 chronic poor premorbid schizophrenics and 48 normal controls reached criterion on a size discrimination task under either praise or censure conditions and then were administered an SG task. Schizophrenics showed significantly greater SG than normals, but no differences were found between the praised and censured groups or between paranoid and nonparanoid schizophrenics. (19 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus generalization as a function of clinical anxiety and direction of generalization.

"This experiment studied stimulus generalization in psychiatric patients as a function of direction of generalization and clinical anxiety. It was found that direction of generalization along the height continuum did not significantly affect the gradient of stimulus generalization. Level of clinical anxiety, as measured by the Taylor Manifest Anxiety Scale, also did not significantly affect the gradient of stimulus generalization. The validity of the Taylor scale with psychiatric patients was discussed briefly." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus generalization and overinclusion in normal and schizophrenic subjects.

Compared 38 male and 12 female schizophrenics and a matched group of normals on a test of stimulus generalization, Epstein's Inclusion Test, and the Vocabulary subtest of the WAIS. Schizophrenics generalized significantly more than normal Ss (p     

Stimulus generalization as a function of clinical anxiety.

"It was hypothesized that the state inferred from manifest clinical symptoms of anxiety would show functionally similar motivational properties to the state of anxiety defined in terms of an implicit response that has been conditioned to situations involving noxious stimulation. It was predicted that both types of anxiety would exhibit the energizing properties of a drive and therefore elevate response gradients of generalization… . The results showed that the groups designated as high in clinical anxiety showed significantly more generalization than the low-clinical anxiety groups under the strong-shock condition. No difference was found between the 2 levels of clinical anxiety for either the weak-shock or buzzer condition." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Additivity of the effects of retention interval and context change on latent inhibition: Toward resolution of the context forgetting paradox.

Three experiments with rats examined retention interval and context switch effects factorially in the latent inhibition paradigm. In Experiment 1, a 28-day retention interval abolished a context switch effect on latent inhibition. In Experiment 2, re-exposure to the contexts before conditioning re-established the context switch effect at the 28-day interval. In this case, the retention interval and context switch effects were additive: Latent inhibition was weakest when the retention interval and context switch were combined. Experiment 3 replicated the context switch effect at the 28-day interval. The results suggest that context switch and retention interval effects may be based on the same process. Context switch effects may weaken over time because physical contexts are embedded in superordinate temporal contexts; animals fail to retrieve physical context when the temporal context changes. This view helps resolve a paradox that has been noted for contextual change theories of forgetting. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus generalization as a function of stimulus novelty and familiarity in rats.

Three experiments used rats as subjects to investigate the generalization of conditioned responding between stimuli as a function of the subjects' exposure to these cues prior to conditioning. Experiment 1 used a between-subjects design, food as the reinforcer, and measured the tendency of subjects to approach the site of food delivery during the stimuli. Generalization of this response was more marked when the training and test stimuli were equated in terms of their novelty (i.e., when both were novel or both were familiar) than when the stimuli differed in this respect (i.e., when one was novel and the other was familiar). Experiments 2a and 2b used within-subjects designs to confirm the reliability of the results of Experiment 1. Implications of these results for current theories of stimulus representation are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus configuration and context effects in perceptual organization in schizophrenia.

Two studies assessed perceptual organization in schizophrenia to determine (a) whether inpatient and outpatient groups with poor premorbid schizophrenia have comparable levels of perceptual organization deficit; and (b) whether the deficit could be eliminated by task manipulations. In Study 1, inpatients demonstrated clear evidence of a perceptual organization deficit, whereas outpatients performed similarly to the control groups. In Study 2, a performance pattern that operationally defined a perceptual organization deficit was eliminated by a task manipulation thought to aid in context processing. The perceptual organization deficit is most pronounced in actively symptomatic patients with poor premorbid schizophrenia, and the deficit reflects, in part, deficient top-down influences to basic perceptual processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Validity generalization in the context of situational models.

A primary objective of validity generalization (VG) analysis is to decompose the between-situation variance in validities into (1) variance attributable to between-situation differences in statistical artifacts and (2) variance attributable to between-situation differences in (unidentified) situational moderators. This process is based on the assumption that the effects of statistical artifacts on validities are independent of the effects of situational moderators on validities. The present article seeks to question the independence assumption by theoretically integrating situational variables into the VG estimation process. It is shown that the independence assumption may be untenable because at least 1 artifact (criterion reliability) is a function of, rather than independent of, the situational variables that moderate validities. An alternative approach to VG analysis is recommended. This approach rests heavily on proactive research designs in which potential situational moderators are included in the generalizability analysis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioning, remembering, and forgetting.

Argues that the separation of theories of learning and of memory should be abandoned. Remembering and forgetting play an important role in simple conditioning experiments. For example, conditioned performance can readily recover after extinction because extinction is susceptible to forgetting. Memory itself involves the kind of associative learning that conditioning experiments are designed to investigate (e.g., conditioning experiments provide insight into the mechanisms of memory retrieval). Learning, remembering, and forgetting all occur within the same biological context; their adaptive functions are therefore intertwined. Taken together, they shed light on some of the mechanisms of clinical relapse. Conditioning theory enriches, and is enriched by, the field of memory as well as other fields of behavioral science. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A contextual change account of the directed forgetting effect.

The authors propose that the costs and benefits of directed forgetting in the list method result from an internal context change that occurs between the presentations of 2 lists in response to a "forget" instruction. In Experiment 1 of this study, costs and benefits akin to those found in directed forgetting were obtained in the absence of a forget instruction by a direct manipulation of cognitive context change. Experiment 2 of this study replicated those findings using a different cognitive context manipulation and investigated the effects of context reinstatement at the time of recall. Context reinstatement reduced the memorial costs and benefits of context change in the condition where context had been manipulated and in the standard forget condition. The results are consistent with a context change account of directed forgetting. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus generalization of suppression in rats following aversively motivated instrumental or Pavlovian training.

Following 100 or 300 avoidance training trials in Exp I, a total of 60 Holtzman male albino rats and their yoked Pavlovian counterparts were tested for generalization of lick suppression along the frequency dimension of the avoidance conditioned stimulus. Gradients of stimulus control were evident after 300 instrumental avoidance training trials, and additional intradimensional Pavlovian discrimination training further sharpened the gradients. After 100 trials, the yoked Pavlovian Ss suppressed more than their instrumental counterparts. However, with increased Pavlovian training, flatter gradients with decreased suppression were obtained. Results from Exp II, using 12 Ss, revealed that, whereas Pavlovian experience decreased suppression to the tone, Ss suppressed drinking in the presence of static, environmental cues. Data from both experiments support interpretations that stress the role of response control over environmental events. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus context effects, associative strength, and word frequency as determiners of free recall in paired-associate learning.

Two levels of response word frequency and three levels of associative strength of paired-associates were used to form six lists. One level of low associative strength between pairs to be learned was created by re-pairing stimuli and responses from high associative strength lists. Both the high associative strength condition and the re-paired condition produced superior recall of response items. Results suggested that the development of response availability in paired-associate learning depends in part not only upon the strength of the initial relationship between each stimulus and response pair to be learned, but also upon the context provided by other stimuli in the list. The meaning of "present at input" in studies evaluating the principle of encoding specificity (Tulving & Thompson, 1973) was questioned. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus preexposure reduces generalization of conditioned taste aversions between alcohol and non-alcohol flavors in infant rats.

Results of 3 experiments showed that infant rats (age 13-17 days) generalize conditioned taste aversions between alcohol and non-alcohol tastes such as a mixture of sucrose and quinine, apple cider vinegar, or coffee. Nonreinforced preexposure to those tastes reduced generalized aversions between them. Generalization between alcohol and sucrose-quinine was reduced not only after preexposure to both tastes, but also when only the nonconditioned taste was preexposed, whereas with alcohol and vinegar, both tastes had to be preexposed to obtain that effect. In no case was generalization reduced when only the to-be-conditioned taste was preexposed. Previous experience with alcohol alone, as well as with similar gustatory stimuli, may enhance subjects' ability to differentiate them during infantile stages in rats. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus familiarization effect and the change effect in children's motor task behavior.

After a review of relevant animal and human adult studies, the present paper summarizes 10 experiments using children as Ss and concerned with 2 empirical phenomena: (1) the stimulus familiarization effect (SFE) the tendency for children to respond faster on various motor tasks to a nonfamiliarized as compared with a previously familiarized stimulus; and (2) the change effect (CE) the tendency for children to respond faster on motor task trials involving a change in stimulus from the immediately preceding trial as compared with trials involving repetition of the stimulus occurring on the preceding trial. It is concluded that the SFE is best accounted for by an orientation reaction (OR) habituation assumption, whereas the CE is probably attributable to preexperimentally acquired sets on the part of children to expect stimulus (or response) change as the more apt to occur (or more apt to be required) event in a 2-stimulus, 2-response experimental situation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pitch perception in chinchillas (Chinchilla laniger): Stimulus generalization using rippled noise.

Rippled noises evoke the perception of pitch in human listeners. Infinitely iterated rippled noise (IIRN) is generated when wideband noise (WBN) is delayed, attenuated, and added to the original WBN through either a positive (+) or a negative (-) feedback loop. The pitch of IIRN[+] is matched to the reciprocal of the delay, whereas the pitch of IIRN[-] for the same delay is an octave lower. Chinchillas (Chinchilla laniger) were trained to discriminate IIRN[+] with a 4-ms delay from IIRN[+] with a 2-ms delay and then tested in a stimulus generalization paradigm with IIRN[+] at delays between 2 and 4 ms. Systematic gradients in behavioral response occurred along the dimension of delay, suggesting that a perceptual dimension corresponding to pitch exists for IIRN[+]. Behavioral responses to IIRN[-] test stimuli were more variable among chinchillas, suggesting that IIRN[-] did not evoke similar pitches relative to IIRN[+]. Systematic gradients in behavioral response were observed when IIRN[-] test stimuli were presented in the context of other IIRN[-] stimuli. Thus, other perceptual cues such as timbre may dominate the pitch cues when IIRN[-] test stimuli are presented in the context of IIRN[+] stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contrast, resistance to extinction, and forgetting in rats.

Conducted 3 experiments with a total of 176 naive male albino rats, in which the depression effect decreased progressively over retention intervals ranging from 1-68 days, which were interpolated between the pre- and postshift stages of a Crespi experiment; at 68 days the depression effect was entirely absent. A 68-day interval between acquisition and extinction eliminated the inverse relationship between resistance to extinction (RTE) and amount of reward in consistently reinforced Ss. The same retention interval eliminated the spaced-trials partial reinforcement effect (PRE) but not the massed-trials PRE. Results are consistent with the views that (a) the inverse relation between RTE and amount of reward is a special case of negative contrast, (b) different mechanisms are responsible for the PRE in massed and spaced trials, and (c) the spaced-trials mechanism is negative contrast. (25 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus configuration, classical conditioning, and hippocampal function.

Hippocampal participation in classical conditioning (CC) is described in terms of a multilayer network that portrays stimulus configuration. The network (1) describes behavior in real time, (2) incorporates a layer of "hidden" units positioned between input and output units, (3) includes inputs that are connected to the output directly as well as indirectly through the hidden-unit layer, and (4) uses a biologically plausible backpropagation procedure to train the hidden-unit layer. Nodes and connections in the neural network are mapped onto regional cerebellar, cortical, and hippocampal circuits, and the effect of lesions of different brain regions is formally studied. Computer simulations of the following CC paradigms are presented: acquisition of delay and trace conditioning, extinction, acquisition–extinction series of delay conditioning, blocking, overshadowing, discrimination acquisition, discrimination reversal, feature-positive discrimination, conditioned inhibition, negative patterning, positive patterning, and generalization. The model correctly describes the effect of hippocampal and cortical lesions in many of these paradigms, as well as neural activity in hippocampus and medial septum during CC… (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus configuration, occasion setting and the hippocampus.

N. A. Schmajuk, J. Lamoureux, and P. C. Holland (in press) showed that an extension of a neural network model introduced by N. A. Schmajuk and J. J. DiCarlo (1992) characterizes many of the differences between simple conditioning and occasion setting. In the framework of this model, it is proposed that the hippocampus modulates (a) the competition among simple and complex stimuli to establish associations with the unconditioned stimulus, and (b) the configuration of simple stimuli into complex stimuli. Under the assumptions that (a) nonselective lesions of the hippocampal formation impair both configuration and competition, and (b) selective lesions of the hippocampus proper impair only stimulus configuration, the model correctly describes the effects of these lesions on paradigms in which stimuli act as occasion setters. (PsycINFO Database Record (c) 2010 APA, all rights reserved)