Distractor effects on latent inhibition are a consequence of generalization decrement

In two experiments rats were exposed to a novel vinegar solution and subsequently given a single conditioning trial on which consumption of vinegar was followed by an injection of lithium chloride. In conformity to other results on distractor effects, the latent inhibition produced by this treatment could be disrupted if the rats drank a second novel solution (sucrose) immediately after their initial exposure to vinegar. But latent inhibition was equally disrupted if rats were initially exposed to vinegar alone and subsequently drank vinegar immediately followed by sucrose on the conditioning trial. Thus latent inhibition was disrupted whenever there was a change between the solutions presented on initial exposure and conditioning trials. Generalization decrement seems the most parsimonious explanation of this pattern of results.     

Distractor effect on the latent inhibition of conditioned flavor aversion in rats

Using a conditioned flavor aversion procedure with rats as subjects, the effect of the addition of a distractor stimulus on the magnitude of the latent inhibition effect was examined. Experiment 1 showed that latent inhibition to vinegar was attenuated by the addition of sucrose during preexposure. On the other hand, sucrose added during conditioning to vinegar did not attenuate latent inhibition. It was also found that the degree of latent inhibition to the vinegar-sucrose compound solution was less when vinegar alone was preexposed (i.e., when sucrose was added only during conditioning) than when the compound solution was preexposed (i.e., when sucrose was added both during preexposure and during conditioning). Experiment 2 gave similar results but with sucrose assigned as the target flavor and vinegar as the distractor. These findings are in full agreement with the generalization decrement account of latent inhibition.     

Poison-enhanced neophobia: Effects of CS-UCSUCS-CS procedures and long-delay training

Experiment 1 (n = 110 male rats) showed that pairing sucrose with toxicosis under forward or backward conditioning procedures yielded reliable poison-enhanced neophobia toward casein hydrolysate. Forward procedures produced reliably greater and more persistent enhancement of neophobia. Experiment 2 (n = 160 male rats) showed that interpolating 10 min, or 1, 4, 8, or 12 hr between sucrose and toxicosis yielded reliable aversion effects to sucrose and poison-enhanced neophobia to casein at each interval except 8 and 12 hr. Generally speaking, the effects of training interval were similar for conditioned aversion and enhanced neophobia but conditioned aversion effects were more enduring.     

Aversion conditioning and enhanced neophobia: role of test stimuli

In Experiment 1, 100 rats (Rattus norvegicus) received 10% sucrose or 5% casein hydrolysate followed, after 10 min, by a LiCl or saline injection or, after 12 h, by a LiCl injection. Subsequently, rats received aversion testing to the CS or neophobia testing to the opposite novel flavor. Aversion effects were reliably greater to casein than to sucrose. However, conditioning with sucrose yielded a reliably greater increase in neophobia to casein (relative to controls) than conditioning with casein yielded to sucrose. In Experiment 2, 60 rats received distilled water followed, after 10 min, by LiCl or saline injection or, after 12 h, by LiCl injection. Aversion effects occurred to distilled water. Neophobia testing to casein and sucrose showed that, relative to controls, neophobia increased reliably more to casein. The results of Experiments 1 and 2 were not attributable to differences in baseline intakes between casein and sucrose flavors. Together, these experiments indicated that the demonstration of conditioning-enhanced neophobia may depend more on the characteristics of the neophobia test flavor than on the strength of aversion established because of CS characteristics.     

Disrupting the conditioned stimulus preexposure effect in flavor-aversion learning: effects of interoceptive distractor manipulations

Rats exposed to a flavor prior to a conditioning trial involving that stimulus learn a significantly diminished flavor aversion relative to nonpreexposed control animals. A series of four experiments investigated the ability of the conditioned stimulus (CS) preexposure effect to be disrupted by the introduction of a distractor flavor stimulus between the preexposure and conditioning episodes. Experiment 1 demonstrated that the preexposure effect could be reduced by a distractor presented immediately following the preexposure. In Experiment 2, it was discovered that a novel distractor was more effective than a familiar distractor, even though both stimuli were sensorily equivalent. Experiment 3 further analyzed the distractor effect and demonstrated that the magnitude of disruption was more pronounced with immediate than with delayed (3 hr) distractor manipulations. Finally, Experiment 4 assessed the effects of the distractor in the absence of CS preexposure. The relation of the results from these experiments to general information theory is discussed.     

Effects of neophobia and habituation on the poison-induced avoidance of exteroceptive stimuli in the rat.

Two experiments on the role of neophobia in poison-induced aversions to exteroceptive stimuli are reported. In Experiment 1, rats were given either 10 or 25 days of habituation to the test situation prior to conditioning. Those animals with the longer habituation period avoided a complex of novel exteroceptive stimuli while those with the shorter habituation period did not. In Experiment 2 rats initially avoided the more novel of two containers, but gradually came to eat equal amounts from both. A single pairing of toxicosis with consumption from either the novel or the familiar container reinstated the avoidance of the novel container in both cases. The results were discussed in terms of an interaction between habituation and conditioning procedures. It was suggested that previously reported differences between interoceptive and exteroceptive conditioning effects may have been influenced by the differential novelty of the two classes of stimuli in the test situation. It was further suggested that non-contingently poisoned control groups should routinely be included in poison avoidance conditioning studies.     

Disengagement of the location negative priming effect: The influence of an intervening response

Reaction time is significantly longer when a target stimulus arises at a location that has just contained a distractor event, relative to when it appears at a new location [i.e., called, the location negative priming (NP) effect]. The NP effect is eliminated when the second of two paired trials (i.e., prime-to-probe trials) predictably lacks a distractor when the preceding trial contains both a target and a distractor event (T+D), but not when a prime distractor appears alone (D-only). We tested the possibility that the failed NP process disengagement seen with D-only prime trials resulted because they do not require the production of an overt intervening response. This possibility was supported. Results also showed that the intervening response had to meet prerequisites; namely, the response had to be prime-generated, i.e., come from the subset of experimental responses and have engaged in a conflict with the prime distractor-activated response.     

Role of telereceptive and interoceptive (taste) cues in ingestional neophobia in chicks (Gallus domesticus)

Experiment 1 investigated the influence of telereceptive (visual) and interoceptive (taste) cues on neophobia by measuring the intakes of clear water and novel solutions of red-colored water, clear 4.0% vinegar, or red-colored 4.0% vinegar in chicks (Gallus domesticus) on 5 test days. Neophobia was reliably greater the more numerous the novel stimuli in testing (i.e., red-colored vinegar) but was similar in magnitude for novel visual and novel taste cues alone. In Experiment 2 chicks received zero, one, or five preexposures to red-colored water or to clear 4.0% vinegar and were tested for neophobia to red-colored 4.0% vinegar. Intake of red vinegar reliably increased with the number of preexposures. However, preexposure to red-colored water facilitated intake of red vinegar more than preexposure to clear 4.0% vinegar did. These results suggest that the familiarity of telereceptive (visual) stimuli attenuates the demonstration of taste neophobia.     

Facilitation and Retardation of Flavour Aversion Conditioning Following prior Exposure to the CS

Two sets of experiments on flavour aversion conditioning in rats examined the effects of the following factors: the nature of the flavour serving as the conditioned stimulus (CS), which was either a compound of monsodium glutamate, sucrose and quinine, or an elemental flavour, either sucrose or dilute acid; the amount of the CS rats consumed on a single conditioning trial-4 ml or 1 ml; and whether rats had been pre-exposed to the CS before this conditioning trial. There were three main findings. First, conditioning to an elemental CS was unaffected by the amount consumed on the conditioning trial, but conditioning to 1 ml of the compound CS was poorer than to 4 ml. Second, pre-exposure produced a latent inhibition effect if the CS was an elemental flavour, or if rats were allowed to drink 4 ml of the compound solution on their conditioning trial. But, third, pre-exposure facilitated conditioning in rats given only 1 ml of the compound solution as their CS.     

The role of probe trial distractors in the production/removal of the spatial negative priming effect

When a current (probe trial) target arises at a location formerly occupied by a distractor event (prime trial; ignored-repetition trial), its reaction time is slower than when it occurs at a previously empty location (control trial), revealing a spatial negative priming (SNP) effect. Here, we examined the influence of prime- and probe trial distractor identity similarity on the retrieval of the stored representations of prime trial processing (i.e., indexed by SNP production), in a context where the prevention of the SNP phenomenon had been motivated (via low probability of probe distractor presence—.25). Two results were important. One, the SNP effect was evident when the prime–probe distractor identities fully matched, but not when they partially or totally mismatched, showing a retrieval role for the probe distractor. Two, target-repeat trial latency facilitation showed the same pattern, indicating that representations of prime target and distractor processing are retrieved together, indicative of an episodic storage format. Since target identity remained fixed, the role of a matching probe distractor identity in SNP production was to presumably complete the triggering requirement (i.e., full event identity matching) for accessing the episodically stored representations.     

在抑制分心物干扰效应上学困生和学优生的比较

采用Stroop颜色命名作业,在严格控制各种条件下探究重复分心物的促进效应是由习惯化机制还是由分心物连续抑制机制造成的问题,进而比较学困生和学优生在Stroop干扰效应、重复分心物促进效应和负启动效应上的差异,结果显示,重复分心物促进效应是由习惯化机制造成的。这种抑制机制,只有在分心物重复条件下才能发挥作用;因而其效用并不广泛;而负启动效应所指的分心物抑制机制却是一种效用广泛的抑制机制。并进而揭示,学困生和学优生都存在重复分心物促进效应,但因学困生的负启动效应比学优生小,所以学困生在Stroop色词干扰效应上大于学优生。     

The role of habituation and attentional orienting in the disruption of short-term memory performance

A series of experiments explored habituation and dishabituation to repeated auditory distractors. Participants memorised lists of visually presented items in silence or while ignoring continuously presented auditory distractors. No habituation could be observed, in that the size of the auditory distractor effect did not decrease during the experiment. However, there was evidence for attentional orienting when novel auditory material was presented after a long period of repetitive stimulation, in that a change of distractors was associated with a temporary decrease in recall performance. The results are most consistent with theoretical accounts that claim that the auditory distractor effect is caused primarily by automatic interference, but that still allow attention to play a limited role in the short-term maintenance of information.     

Contextual Pavlovian conditioning in the crab Chasmagnathus

In contextual conditioning, a complex pattern of information is processed to associate the characteristics of a particular place with incentive or aversive reinforcements. This type of learning has been widely studied in mammals, but studies of other taxa are scarce. The context-signal memory (CSM) paradigm of the crab Chasmagnathus has been extensively used as a model of learning and memory. Although initially interpreted as habituation, some characteristics of contextual conditioning have been described. However, no anticipatory response has been detected for animals exposed to the training context. Thus, CSM could be interpreted either as an associative habituation or as contextual conditioning that occurs without a context-evoked anticipatory response. Here, we describe a training protocol developed for contextual Pavlovian conditioning (CPC). For each training trial, the context (conditioned stimulus, CS) was discretely presented and finished together with the unconditioned stimulus (US). In agreement with the CSM paradigm, a robust freezing response was acquired during the 15 training trials, and clear retention was found when tested with the US presentation after short (2 and 4 h) and long (1–4 days) delays. This CPC memory showed forward but not simultaneous presentation conditioning and was context specific and protein synthesis dependent. Additionally, a weak CPC memory was enhanced during consolidation. One day after training, CPC was extinguished by repeated CS presentation, while one presentation induced a memory labilisation–reconsolidation process. Finally, we found an anticipatory conditioned response (CR) during the CS presentation for both short-term (4 h) and long-term memory (24 h). These findings support the conditioning nature of the new paradigm.     

Can the location negative priming process operate in a proactive manner?

The location negative priming (NP) effect refers to the fact that the processing of a current target stimulus (probe trial) is delayed when it appears at a location that has recently contained a distractor event (prime trial), relative to when it occurs at a previously unoccupied position. One view is that the process causing the NP effect involves the inhibition of the internal representation of the prime-distractor event, and that the future processing of target stimuli that involve this event are prolonged because this distractor inhibition is persistent. In this study, we examined the possibility that the NP process (inhibition) could act proactively; specifically asking whether inhibition could be allocated to a location merely predicted to hold a future distractor event. To do this, we cued the probe distractor's location using an otherwise traditional location NP paradigm. No evidence of a proactive NP process was obtained. Probe-trial target latency was the same whether it appeared at the cued distractor location or at a new location, but was delayed when it occupied the prime-distractor location (NP effect). The location NP process is seemingly a reactive one, applying inhibition only when an actual distractor is present, much as past theories have implied.     

Rats (Rattus norvegicus) selectively bred to differ in avoidance behavior also differ in response to novelty stress, in glycemic conditioning, and in reward contrast

The behavior of the Syracuse high avoidance (SHA) and Syracuse low avoidance (SLA) rats, selectively bred by Brush (F. R. Brush, J. C. Froehlich, & P. Sakellaris, 1979, Behavior Genetics, 9, 309-316) to differ in avoidance behavior, was examined in several different tasks. The SLA rats showed a greater elevation in plasma glucose when exposed to a novel environment; after 7 days of exposure to this environment there was evidence of habituation in the SHA rats but not in the SLA rats; the SHA rats showed a hyperglycemic conditioned response in a glycemic conditioning procedure, the SLA rats showed no evidence of conditioning but had higher overall levels of plasma glucose; both strains showed reliable successive negative contrast effects in consummatory behavior when shifted from 32 to 4% sucrose, but the contrast was larger in the SLA rats; the administration of chlordiazepoxide eliminated negative contrast in the SLA rats but had no effect on contrast in the SHA rats; and the SLA rats were reliably heavier than the SHA rats. The behavioral differences were considered in the context of differences in emotional reactivity between the two strains.     

Learned preference for a hedonically negative flavor is observed after pairings with positive post-ingestion consequences rather than with a palatable flavor

In two experiments, thirsty rats consumed a compound of sucrose and a non-preferred flavor. In Experiment 1, a conditioned preference was observed in the experimental group when animals were tested both thirsty and hungry, but not when they were tested just thirsty. Animals in the control group, which experienced the flavor and the sucrose unpaired, never showed a preference. Experiment 2 replicated the absence of a preference in the experimental group when rats were tested thirsty, but provided evidence that a flavor-taste association had been formed during training. After conditioning, sucrose was paired with LiCl in group Dev whereas it was unpaired in group NonDev. The sucrose devaluation produced a decrease in CS preference in group Dev, and an increment in group NonDev. Taken together, these results show that preference for a non-preferred flavor can be readily observed after pairings with the positive consequences of the US (calories or absence of an expected illness) rather than with a palatable flavor.     

Potentiation of odor by taste in rats: tests of some nonassociative factors

The contribution of nonassociative neophobia and sensitization to the potentiation of odor by taste in rats was tested in three experiments. In Experiment 1, neophobia for almond odor (O), saccharin taste (T), and odor-taste compound (OT) cues was tested before and after noncontingent lithium chloride poisoning and compared with conditioned aversions produced by OT-LiCl temporal pairing. The OT compound potentiated unconditioned neophobia, but there was no evidence of poison-enhanced neophobia, disinhibition of neophobia, or sensitization by noncontingent LiCl; temporal pairing produced aversions for the compound and its elements. In Experiment 2, generalization to a novel odor was tested after O-LiCl or compound OT-LiCl pairing. The potentiated odor aversion did not generalize to the novel odor; it was specific to the odor paired with taste and LiCl. In Experiment 3, potentiation of the odor component by a discriminant or nondiscriminant taste component was tested. Potentiation was evident only when a novel discriminant taste was in compound with odor prior to LiCl poisoning. These studies support an associative "indexing" hypothesis of the potentiation effect in rats.     

Mere exposure to telereceptive cues facilitates intake of a novel flavor in chickens (Gallus domesticus)

This experiment investigated whether mere exposure to visual cues of a distinctively colored solution (water) would facilitate intake of a novel flavor (vinegar) of the same distinctive color. Eighty-four chicks received access to clear water, clear vinegar, red water, or red vinegar under conditions which permitted drinking or they received access to clear water or red water under conditions (mere exposure) which prevented drinking. All chicks were then tested on intake of red vinegar. Chicks which had received mere exposure or ingestional experience with red-colored water drank reliably more red vinegar than did chicks which had received prior ingestional experience with the novel taste, vinegar, but not with the visual cues of red. However, intake of red vinegar was reliably greater following ingestional experience with red water than following visual exposure without ingestion. Results supported the mere exposure hypothesis.     

Current versus past ambiguity in intertrial priming

Visual search is speeded when the target is repeated from trial to trial compared to when it changes, suggesting that selective attention learns from previous events. Such intertrial effects are stronger when there is more competition for selection, for example in ambiguous displays where the target is accompanied by a salient distractor. Here we investigate whether this is because the competition strengthens the learning itself, or because it allows for a learned representation to exert a greater effect. The results point to the latter. Observers looked for a colour-defined target that could repeat or change from trial to trial. A salient distractor could be present on the current trial, the previous trial, both, or neither. Intertrial effects were greater when a distractor was present on the current trial, suggesting that a primed target representation is more beneficial under conditions of competition. In contrast, distractor presence on the previous trial had no effects whatsoever, indicating that the learning process itself is not affected by competition. This suggests that the source of the learning resides at postselection stages, whereas the effects may occur at the perceptual level.     

Developmental flavor experience affects utilization of odor, not taste in toxiphobic conditioning

Feeding experiences were varied in developing rats and the effects upon flavor neophobia and lithium chloride-induced flavor aversions were observed. In Experiment 1, nursing experience of neonate rats was reduced by artificial feeding via intragastric cannula; the rats then were tested with apple juice paired with lithium chloride injection at weaning or maturity. Conditioned aversions were not affected, but neophobia to novel apple juice was attenuated in artificially-reared rats tested at maturity. In Experiment 2, rats received enriched feeding experience after weaning, which consisted of (a) obtaining many complex flavors, a few of which were paired with poisoning, effortlessly in the home cage, or (b) foraging for various foods on an elevated maze. No dramatic effects on neophobia or conditioned taste aversion for saccharin water were apparent. In Experiment 3, rats were given experience after weaning with vanilla-scented water either paired or unpaired with quinine water, and then tested with the odor of almond or that odor compounded with saccharin water for neophobia and lithium-induced aversions. Flavor-experienced rats exhibited more pronounced odor conditioning and more resistance to extinction of the odor aversion after both simple and compound conditioning. In contrast, saccharin taste aversions were relatively unchanged. Apparently, enriched feeding and drinking experience facilitates the utilization of odor more than taste cues.