Development of food recognition in young chicks: III. Discrimination.

Previous studies show that the pecking rate of naive 3-day-old chicks increases after ingestion of food and decreases after ingestion of sand, but these changes have not been specific to the stimulus that was ingested. In the present experiments with a total of 450 Burmese Red Junglefowl chicks, Exps I and II showed that neither 1 nor 4 10-min simultaneous-choice tests were sufficient for discrimination to be shown between food and sand. Exp III showed that many hours of experience with food or sand were sufficient for discrimination if Ss were tested for 10 min with only 1 stimulus at a time. Similar results were found in Exp IV in which Ss had only 10 min of experience with food or sand. Pecking rates to food and sand were the same during the 1st 2 min of the test and only later diverged. These results imply that the discrimination is based on feedback that develops 2-3 min after ingestion but develops only if chicks have had previous experience with food or sand. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of food recognition in young chicks: I. Maturation and nutrition.

Investigated age and food ingestion as factors influencing food recognition in 5 experiments with a total of 338 Burmese Red Junglefowl chicks. Newly hatched chicks pecked indiscriminately at sand and food; by 3 days of age, pecks were directed primarily at food. Pecking at food or sand had little effect on subsequent pecking at either stimulus until the chicks were 2-3 days old. Ingestion of food then served to facilitate pecking, but such facilitation did not occur until 10 min to 1 hr after ingestion. The effects that occurred on Day 3 were not specific to the stimulus pecked, but pecking at food and sand increased in frequency when the chicks had ingested food. Control experiments using a forced-feeding technique showed that these effects were due to ingestion of food and occurred only if food ingestion was associated with pecking. (16 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of food recognition in young chicks: II. Learned association over long delays.

Reports that the pecking rate of 3-day-old Burmese Red Junglefowl chicks (n = 60) increased markedly 40-80 min after they had ingested their first food. Varying the amount of food ingested by Ss (n = 80) in a 2nd experiment had no effect on the time when increased pecking appeared. Ss with prior experience with food (n = 45) did not show an increase in pecking. Results indicate that satiation and hunger are not responsible for the delayed increase in pecking and, taken together with previous results, provide strong support for the hypothesis that the increased pecking seen in these experiments is an example of learning that occurs with a delay of reinforcement of about 1 hr. (15 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Tolerance to morphine in the rat: Associative and nonassociative effects.

Two experiments were conducted to examine the impact of dose level and interdose interval (IDI) on the development of tolerance to the analgesic effect of morphine. In Exp I, rats were administered a series of low- (5 mg/kg) or high- (30 mg/kg) dose injections of morphine either explicitly paired or unpaired with a distinctive context at a 48-hr IDI. The development of tolerance following this regimen was assessed by shifts in dose-response curves to the right when animals were tested on a tail-flick device in the distinctive context. Only animals that had received morphine paired with the distinctive context were tolerant to morphine; the magnitude of this associative tolerance was a positive function of the level of the conditioning dose. In Exp II, rats were exposed to a high dose of morphine (30 mg/kg) either paired or unpaired with a distinctive context at one of two IDIs (24 or 96 hr). Tolerance testing revealed that at the long IDI, only associative tolerance was evident, whereas at the short IDI, tolerance in the unpaired condition was more pronounced with a corresponding decline in the development of associative tolerance. The relevance of these findings for psychological theories of drug tolerance are discussed. Results are consistent with the predictions of an habituation model of drug tolerance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Associative and nonassociative tolerance: the effects of dose and interdose interval

Two experiments examined the effects of dose and interdose interval (IDI) on associative and nonassociative tolerance to morphine analgesia in rats. Associative contingencies were manipulated by administering low (5 mg/kg) or high (20 mg/kg) doses of morphine explicitly paired or unpaired with a distinctive context. Nonassociative processes were manipulated by administering morphine at a short (6-h) or long (96-h) IDI. Tolerance was assessed as shifts in morphine dose-response curves on the tail-flick test. Animals in the long IDI conditions showed considerable context-specific tolerance. Tolerance in the short IDI conditions was not influenced by contextual contingencies at the immediate test (Experiment 1) and showed no retention over a 30-day interval (Experiment 2), suggesting this tolerance was nonassociative. The impact of massed exposure to morphine and context on the disruption of learning at the short IDI is discussed.     

Associative interference effects in recognition and recall.

The results of 3 studies testing whether associative interference occurs in recognition as it does in recall are reported. Associative interference was found as expected in cued recall, but it did not occur in recognition. Rather, in recognition, both the hit rate and the false alarm rate increased under interference conditions so that there was no net change in discrimination. The design of the recognition studies enabled the rejection of displaced backward rehearsals and variance differences in the matching strengths of interference and noninterference pairs as artifactual explanations of the results. The presence of associative interference in recall, but not in recognition, supports the distinction put forward by the global matching models of recognition that there is a fundamental difference between the memory access processes underlying recognition and recall. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Latent inhibition in rats: Associative or nonassociative?

Preexposure to a stimulus usually retards subsequent conditioning involving the stimulus. Associative and nonassociative explanations of this effect, termed latent inhibition, predict differential effects if the pre-exposed stimulus is subsequently made a positive or negative CS (S+ or S-, respectively). In an experiment with 42 male Sprague-Dawley rats, Ss previously trained to press a lever on visually cued discrete trials received either 0 or 200 pre-exposures to a 1,000-Hz tone. Ss were then trained on a successive discrimination in which the tone became a signal either for the reinforcement or nonreinforcement of leverpressing. Pre-exposed Ss ceased responding on S- trials significantly more slowly than did Ss that were not pre-exposed, regardless of whether the tone became an S+ or an S-. Nonassociative explanations of latent inhibition are supported by this finding. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Associative and nonassociative theories of the UCS preexposure phenomenon: Implications for Pavlovian conditioning.

Excitatory Pavlovian conditioning of a discrete CS is attenuated by prior exposure to the UCS. The UCS preexposure phenomenon is observed in a variety of Pavlovian conditioning procedures as diverse as eyelid conditioning, the conditioned emotional response, and conditioned taste aversion learning. This article discusses the variables that affect the UCS preexposure phenomenon and uses this information in evaluating both associative and nonassociative accounts of the phenomenon. At least one associative account, based on context blocking, and at least one nonassociative account, based on central habituation of the emotional response to the UCS, remain viable. (71 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of brightness preferences in young chicks: Effects on brightness discrimination learning.

Conducted 7 experiments with a total of 256 1-3 day old Vantress * Arbor Acre chicks to investigate the effects of interactions between the S and its sensory environment on both emergence of brightness preferences and modification by conditioning. In a simultaneous brightness discrimination, Ss were rewarded with heat for approaching either a bright or dim stimulus. Results indicate (a) brightness preference was so stable that it could not be eliminated by incubating, hatching, and rearing in the dark; (b) light experience significantly increased this preference; and (c) modification of this preference by heat reinforcement depended on age of S, prior rearing condition, sensory stimulation between testing sessions, and the length of interval between testing sessions. (28 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A method for measuring generalization of imprinting effects in young chicks.

Describes 2 experiments, with a total of 180 Ross chicks as Ss, in which an attempt was made to construct a continuum of imprinting stimuli, together with a new method, the "stationary wheel," of estimating approach tendencies in young chicks. Ss were imprinted with 1 member of the continuum and either divided into subgroups, each of which was tested on 1 value of the continuum (Exp I), or tested on all values of the continuum (Exp II). Approach scores showed a significant decrement away from the training value at whichever end of the continuum chicks were trained. Results show that the stationary wheel method yielded replicable approach data without the disadvantages inherent in the "arena-type" method of measurement. Analyses of a number of other measures, including peep calls, twitter calls, and approach orientation, are also discussed. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Discrimination of small numerosities in young chicks.

Chicks were trained to discriminate small sets of identical elements. They were then tested for choices (unrewarded) between sets of similar numerosities, when continuous physical variables such as spatial distribution, contour length, and overall surface were equalized. In all conditions chicks discriminated one versus two and two versus three stimulus sets. Similar results were obtained when elements were presented under conditions of partial occlusion. In contrast, with sets of four versus five, four versus six, and three versus four elements chicks seemed unable to discriminate on the basis of number, although nonnumerical discrimination based on perceptual cues was observed. This adds to increasing evidence for discrimination of small numerosities of up to three elements in human infants and nonhuman animals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Associative learning and recognition memory in alcoholic Korsakoff patients.

Association learning and recognition memory were examined in 8 male alcoholic Korsakoff patients (mean age 58 yrs), and in the following 4 groups of 10 men: non-Korsakoff alcoholics (mean age 59 yrs), nonalcoholic controls (mean age 64 yrs), younger alcoholics (mean age 36 yrs), and nonalcoholic controls (mean age 37 yrs). The tasks were modeled after those used for testing memory functioning in nonhuman primates. Association learning, defined as the ability to distinguish rewarded from equally familiar nonrewarded visual stimuli, was impaired in Korsakoff patients. Korsakoff patients also were impaired on recognition memory—the ability to discriminate familiar from novel items. Results support the view of loss of multiple memory functions in alcoholic amnesia. An effect of aging was indicated by differences in performance levels between younger and older groups of non-Korsakoff participants, although the latter were superior to the Korsakoff patients. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of similarity and experience on discrimination learning: A nonassociative connectionist model of perceptual learning.

This article describes a novel connectionist model of perceptual learning (PL) that provides a mechanism for nonassociative differentiation (J. J. Gibson & E. J. Gibson, 1955). The model begins with the assumption that 2 processes—1 that decreases associability and 1 that increases discriminability—operate during preexposure (S. Channell & G. Hall, 1981). In contrast to other models (e.g., I. P. L. McLaren, H. Kaye, & N. J. Mackintosh, 1989), in the current model the mechanisms for these processes are compatible with a configural model of associative learning. A set of simulations demonstrates that the present model can account for critical PL phenomena such as exposure learning and effects of similarity on discrimination. It is also shown that the model can explain the paradoxical result that preexposure to stimuli can either facilitate or impair subsequent discrimination learning. Predictions made by the model are discussed in relation to extant theories of PL. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Form preferences in successive discrimination learning of young chicks.

In 4 experiments the effects of form and orientation pecking preferences of a total of 100 1- and 3-day old Vantress X Arbor Acre chicks on successive discrimination learning were determined using heat reinforcement. Results indicate that (a) the young chick has both circle and vertical orientation pecking preferences that are present during at least the 1st 3 days after hatching; (b) when either of these preferred cues is the nonreinforced cue, the young chick has difficulty in learning not to respond to it but learns quickly not to respond to an unpreferred cue; and (c) these pecking preferences can be modified by heat reinforcement, and the effects of this conditioning is evident in subsequent extinction and retention tests. It is concluded that form and orientation preferences, like brightness and color preferences, are important developmental constraints on conditioning of the young chick. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Trial-spacing effects in Hermissenda suggest contributions of associative and nonassociative cellular mechanisms.

In behaving Hermissenda, a preparatory conditioned response developed across repeated pairings of light (conditioned stimulus; CS) and rotation (unconditioned stimulus; US) with intertrial intervals (ITIs) of 60 and 120 s, but not 30 s. Likewise, contiguous in vitro stimulation of the visual and vestibular receptors, an analog of behavioral conditioning, resulted in an increase in the input resistance (i.e., excitability, a correlate of conditioning) of the B photoreceptors of the Hermissenda's eye, but only with ITIs greater than 60 s. Calcium signaling in the B cell, critical to the induction of this neuronal plasticity, was attenuated with shorter ITIs owing to (a) a reduction of the light-induced generator potential and hence voltage-dependent Ca2+ influx during the light CS, (b) a depression of the Ca2+ current that persisted throughout shorter ITIs, and (c) a steady-state inactivation of the Ca2+ current as a result of a sustained depolarization persisting from the previous trial. These results are consistent with a 2-process theory of associative learning in which a primary process (Ca2+ influx) may be opposed by a secondary process (depression of the Ca2+ current) during short ITIs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Associative priming in bilinguals: Some limits of interlingual facilitation effects.

Examined how the prior visual presentation of a word from one of a bilingual S's languages can facilitate the identification of an associated word from the other language. Results from performance on lexical decision tasks with 72 Ss show a different pattern of effects for intra- and interlingual conditions at 2 different stimulus onset asynchronies (SOAs). At a short SOA, no facilitation effect was observed between associated words from different languages. At a long SOA, facilitation was observed for both between- and within-language conditions, but the between-language effect was weaker. Results do not suggest direct interlingual links in the bilingual lexicon. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of initial-pecking consequences on subsequent pecking in young chicks.

White Leghorn cockeral chicks ? and 2? days old received saline or LiCl injection immediately following their 1st feeding experience. When retested 5 hrs later 2?-day-old Ss that had received saline increased their pecking rate, but ?-day-old Ss showed no change. Only 2?-day-old chicks, therefore, appear to associate ingestion of food with long-term positive consequences. Ss of both ages, on the other hand, greatly reduced pecking when retested 5 hrs after LiCl injection. Thus, ?- and 2?-day-old chicks are capable of forming an association between pecking and its long-term consequence when the consequence is aversive. When LiCl injection was not contingent on pecking, following the initial feeding session by 6 hrs, Ss did not reduce retest pecking rates. (7 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Associative deficit in recognition memory in a lifespan sample of healthy adults.

Advanced age is associated with decrements in episodic memory, which are more pronounced in memory for associations than for individual items. The associative deficit hypothesis (ADH) states that age differences in recognition memory reflect difficulty in binding components of a memory episode and retrieving bound units. To date, ADH has received support only in studies of extreme age groups, and the influence of sex, education, and health on age-related associative deficit is unknown. We address those issues using a verbal paired-associate yes–no recognition paradigm on a lifespan sample of 278 healthy, well-educated adults. In accord with the ADH, greater age was associated with lower hit and greater false alarm rates and more liberal response bias on associative recognition tests. Women outperformed men on recognition of items and associations, but among normotensive participants, women outperformed men only on memory for associations and not on item recognition. Thus, although supporting ADH in a large lifespan sample of healthy adults, the findings indicate that the effect may be partially driven by an age-related increase in liberal bias in recognition of associations. Sex differences and health factors may modify the associative deficit regardless of age. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reevaluating evaluative conditioning: A nonassociative explanation of conditioning effects in the visual evaluative conditioning paradigm.

In 2 studies, the authors investigated whether evaluative conditioning (EC) is an associative phenomenon. Experiment 1 compared a standard EC paradigm with nonpaired and no-treatment control conditions. EC effects were obtained only when the conditioned stimulus (CS) and unconditioned stimulus (UCS) were rated as perceptually similar. However, similar EC effects were obtained in both control groups. An earlier failure to obtain EC effects was reanalyzed in Experiment 2. Conditioning-like effects were found when comparing a CS with the most perceptually similar UCSs used in the procedure but not when analyzing a CS rating with respect to the UCS with which it was paired during conditioning. The implications are that EC effects found in many studies are not due to associative learning and that the special characteristics of EC (conditioning without awareness and resistance to extinction) are probably nonassociative artifacts of the EC paradigm. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Associative strength as a mode of organization in recall and recognition: A comparison of schizophrenics and normals.

In 2 experiments, word pairs of high and low intrapair association were presented to a total of 40 schizophrenic and 40 normal adults. In Exp I, 1 member of each pair in both recall and recognition tasks was also displayed as a cue at the time of response. The number of words correctly recalled and recognized by both schizophrenics and normals was markedly greater for high-association lists. On high-association lists, schizophrenic performance was inferior to that of normals. The same lists were used in Exp II, which required the recognition of both words in each pair. Normal recognition was superior only for high-association lists. Results are interpreted as supporting the view that because schizophrenics did not subjectively organize or encode information when presented, subsequent retrieval was deficient. (PsycINFO Database Record (c) 2010 APA, all rights reserved)