Type of feature affects transfer in operant serial feature-positive discriminations

In two experiments, the effects of feature identity in operant serial feature-positive discriminations were examined with rats. Rats were trained with two serial feature-positive discriminations (F1 → T1+/ T1? and F2 → T2+/ T2?), in which different operants were reinforced with delivery of a sucrose solution during two auditory target cues (T1 and T2). The features (F1 and F2) were two visual cues, two flavored sucrose solutions, or one visual cue and one sucrose solution. Transfer of a feature’s control to the target of the other discrimination was observed only when the features were from the same modality. When observed, transfer responding was of the form originally trained to the target, rather than the feature, and was preserved after feature extinction. Control groups showed that the differential transfer was not solely the consequence of differential feature generalization. Implications for theories of occasion setting are discussed.     

Contextual control of pavlovian feature-positive and feature-negative discriminations

Three pigeons were trained with a Pavlovian serial feature-positive (F-P) discrimination task in a light context, in which the houselight was on, and with a Pavlovian serial feature-negative (F-N) discrimination task in a dark context, in which the houselight was off. Three other pigeons were trained with the F-P task in the dark context and the F-N task in the light context. These two contextual conditions were changed randomly trial by trial. The former birds learned the tasks within 60 sessions, by responding exclusively to the target keylight after the feature tone in the light context and by responding exclusively to the target not preceded by the feature in the dark context. Two of the latter birds required separate training of the F-P and the F-N tasks to acquire the discrimination: responding exclusively to the target after the feature in the dark context and responding exclusively to the target not preceded by the feature in the light context. The third bird, however, failed to learn the discrimination even with separate training. These results indicate that the four-term contingency (the context-feature-target-food relationship) controlled the birds’ behavior in the Pavlovian setting. The insertion of a temporal gap between the feature and the target impaired the F-N discrimination, although it had little effect on the F-P discrimination.     

Pigeons’ memory for event duration: Intertrial interval and delay effects

The effects of within-session variations in the intertriai interval (ITI) and delay on pigeons’ memory for event duration were studied in delayed symbolic matching-to-sample tasks. Pigeons were trained to peck one color following a long (8 sec) sample and another color following a short (2 sec) sample. In the first three experiments, the baseline conditions included a 10-sec delay (retention interval) and a 45-sec ITI. During testing, the delay was varied from 0 to 20 sec, and the ITI that preceded the trial was varied from 5 to 90 sec. When the ITI and delay were manipulated separately (Experiments 1 and 2), the pigeons displayed a choose-short tendency when the delay was longer than 10 sec or when the ITI was longer than 45 sec, and a choose-long tendency when either the delay or the ITI was shorter than these baseline values. These effects occurred whether the sample was food access or light. When the ITI and delay were manipulated together, the pigeons showed a large choose-long error tendency when the short delay was tested together with a short ITI, and no systematic error tendency when the short delay was tested together with a longer ITI. A very large choose-short error tendency emerged on trials with a long delay and a long ITI; a reduced choose-short tendency was present when the long delay was presented together with a short ITI. In Experiment 4, the baseline conditions were a 0-sec delay and a 45-sec ITI. In this case variations in the ITI had a smaller and unidirectional effect: the pigeons showed a choose-long error tendency when the ITI was decreased, but no effect of ITI increases. Two hypotheses were proposed and discussed: (1) that pigeons judge sample durations relative to a background time composed of the ITI and delay, and (2) that the delay and ITI effects might arise from a combination of subjective shortening and proactive effects of samples from previous trials.     

Intertrial interval and unconditioned stimulus durations in autoshaping

Four groups of pigeons were exposed to an autoshaping procedure in which a 20-sec key illumination preceded the presentation of response-independent grain, The groups differed according to the duration of feeder access and the intertriai intervals, If feeder durations are not included in the time between trials, two of the groups had identical intertriai intervals. If feeder durations are included, each of the other two groups was identical to one of the first two in terms of the intertriai interval, The speed of acquisition and maintained measures of responding were directly related to the duration of the interval from food offset to signal onset, Groups exposed to equivalent intertriai intervals and different feeder durations did not differ from one another on these measures, The results were interpreted as evidence that feeder durations were not included in the functional intertrial interval and that feeder duration, per se, did not affect autoshaped responding.     

Intertrial interval and passive avoidance learning inOctopus vulgaris

WhenOctopus vulgaris were trained on a passive avoidance task at various intertrial intervals from 0.05 to 10 min, acquisition rate was maximal at the intermediate intervals, a finding similar to those obtained with rats. Explanations involving fear are thought to be inadequate and the phenomenon is interpreted in terms of short-term memory.     

Conditioning of simultaneous and serial feature-positive discriminations

Three experiments with rat subjects examined the development of simultaneous and serial feature-positive discriminations in appetitive conditioning. In Experiment 1, reinforced presentations of a simultaneous light-tone compound were intermixed with nonreinforced presentations of either the light or the tone. The compound stimulus acquired conditioned behaviors of a form characteristic of the predictive feature alone; the element common to reinforced and nonreinforced trials did not evoke conditioned behavior. In Experiment 2, reinforced presentations of a serial light-trace-tone compound were intermixed with nonreinforced tone-alone presentations. The light feature stimulus acquired conditioned behaviors characteristic of visual CSs. The tone stimulus, common to reinforced and nonreinforced trials, evoked conditioned behaviors characteristic of auditory CSs, but only when preceded by the light. In Experiment 3, variations in the interval between the light and tone on reinforced trials had little effect on responding to the light CS but substantially altered the pattern of responding to the tone CS. These results suggested that simultaneous and serial feature-positive discriminations may be solved differently. Performance in simultaneous feature-positive discriminations may be determined solely by associations between the feature stimulus and the reinforcer, but performance in serial discriminations may also involve the acquisition of a conditional cue function to the feature.     

Effects of interrun interval on serial learning

Two groups of five rats each received a decreasing quantity of food reward, 14-7-3-1-0 .045-g food pellets, over successive runs in a runway. The interrun interval (IRI) separating runs within each of two daily pattern repetitions (trials) was 10 sec (short, S) or 4–5 min (long, L) and varied over four successive phases of training in the order indicated by the group names, that is, Groups SLSS and LLLS. Anticipation of the 0-pellet element developed more rapidly in Group SLSS than in Group LLLS, but did eventually occur at the long IRI. Anticipation was eliminated by the increase in IRI experienced by Group SLSS in Phase 2 and by the decrease in IRI experienced by Group LLLS in Phase 4. The results are discussed with reference to the effects of changes in stimulus context accompanying IRI shifts on retrieval of task-specific knowledge and with reference to the possible signal value established to IRI-specific stimuli.     

Midsession reversals with pigeons: visual versus spatial discriminations and the intertrial interval

Discrimination reversal learning has been used as a measure of species flexibility in dealing with changes in reinforcement contingency. In the simultaneous-discrimination, midsession-reversal task, one stimulus (S1) is correct for the first half of the session, and the other stimulus (S2) is correct for the second half. After training, pigeons show a curious pattern of choices: They begin to respond to S2 well before the reversal point (i.e., they make anticipatory errors), and they continue to respond to S1 well after the reversal (i.e., they make perseverative errors). That is, pigeons appear to be using the passage of time or the number of trials into the session as a cue to reverse, and are less sensitive to the feedback at the point of reversal. To determine whether the nature of the discrimination or a failure of memory for the stimulus chosen on the preceding trial contributed to the pigeons’ less-than-optimal performance, we manipulated the nature of the discrimination (spatial or visual) and the duration of the intertrial interval (5.0 or 1.5 s), in order to determine the conditions under which pigeons would show efficient reversal learning. The major finding was that only when the discrimination was spatial and the intertrial interval was short did the pigeons perform optimally.     

A feature positive effect in conditioned suppression

A conditioned suppression experiment with rats studied the development of two discriminations involving two conditioned stimuli, A and X. In one discrimination (AX+/A?), compound presentations of A and X signaled shock and presentations of A alone signaled no-shock. In the other discrimination (A+/AX?), A alone signaled shock and AX signaled no-shock. AX+/A? discriminations were learned more rapidly than their A+/AX? counterparts. These results, which resemble the feature-positive effect of Jenkins and Sainsbury (1969, 1970), are discussed in terms of Rescorla and Wagner’s (1972) theory of conditioning and also in terms of stimulus intensity mechanisms.     

Trial spacing effects in pavlovian conditioning: A role for local context

Two conditioned lick-suppression experiments with rats were conducted in order to replicate and extend findings by Ewing, Larew, and Wagner (1985). Ewing et al. observed that excitatory responding to a CS paired with a footshock US was attenuated when the ITIs thatpreceded each CS-US trial were short (60 sec) relative to when they were long (600 sec). This effect was isolated in the influence of the preceding ITI because the preceding ITI was consistently short for one CS and consistently long for a different CS, while the following ITIs were equally often short and long for both CSs. Ewing et al. interpreted this finding in the framework of Wagner’s (1981) SOP model. Experiment 1 replicated this trial-spacing effect and demonstrated a similar effect under conditions in which thefollowing ITI was consistently short for one CS and consistently long for a different CS, while the durations of preceding ITIs were equally often short and long for both CSs. Experiment 2 revealed that the detrimental effect of a short preceding or a short following ITI could be alleviated by extinguishing the conditioning context after CS-US training. The latter observation indicates that the trial-spacing effect is not mediated by a failure of a CS trained with a short ITI to enter into excitatory associations with the US, a conclusion that is not wholly consistent with the SOP model. Finally, we suggest that short pretrial and short posttrial ITIs may enhance the excitatory value of local context cues that modulate responding to a CS.     

基于区间型特征向量的模式识别方法

由于客观事物的复杂性和不确定性以及人类思维的模糊性,在模式识别中所要刻画的特征信息往往不是以具体的数值来表示,而是以区间数的形式表示.本文首先基于区间数的中点和宽度以及中点影响因子和宽度影响因子给出区间数距离的计算方法,进一步考虑到诸特征在识别中所占有的重视程度给以赋权,并给出贴近度计算及择近原则.在此基础上,建立模式识别的方法.     

Memory interval distribution effects in pigeons

Pigeons were trained with two concurrent delayed conditional discriminations that involved different distributions of memory intervals, namely 1 and 5 sec in the “short” and 5 and 10 sec in the “long” distribution. Memory for the initial stimulus was much better after 5 sec in the short distribution than in the long one. The memory functions between the intervals within each distribution were essentially flat. These findings were replicated in a second study that involved differential outcomes; this procedure enhanced memory generally within trials so that memory intervals of 1, 9, and 19 sec could be used, with 9 sec serving as the common memory interval. The findings are interpreted on the basis of the subject’s expectation of the likely duration of the upcoming memory interval and the associated delay of reinforcement.     

Response variability in pigeons in a pavlovian task

Instrumental response variation is inversely related to reward probability. Gharib, Derby, and Roberts (2001) theorized that individuals behave more variably when their expectation of reward is low. They postulate that this behavioral rule assists the discovery of alternative actions when a target response is unlikely to be reinforced. This suggests that response variability may be unaffected in a situation in which an animal’s behavior is inconsequential to outcome delivery. We trained 6 pigeons in a within-subjects Pavlovian autoshaping procedure. On any given trial, the pigeons were presented with one of six colored discs on a touchscreen; each stimulus was associated with a particular probability of food, ranging from 100% to 0.6%. Pecking was more variable with low probabilities of food delivery, thus extending the rule relating variability and expectation to a Pavlovian situation.     

Item feature effects in evolution assessment

Despite concerted efforts by science educators to understand patterns of evolutionary reasoning in science students and teachers, the vast majority of evolution education studies have failed to carefully consider or control for item feature effects in knowledge measurement. Our study explores whether robust contextualization patterns emerge within particular evolutionary reasoning contexts, and the implications of these patterns for instruction, assessment, and models of cognition. We test four hypotheses regarding item feature effects on undergraduate biology majors' evolutionary reasoning using a sample of 1,200 open response explanations of evolutionary change across items differing in context and scale but standardized by taxon and trait. Evolutionary explanations were atomized into a series of scientific and naïve biological elements and tallied among prompts and their features. We documented clear, significant, and predictable item feature effects on evolutionary explanations. Tasks involving evolutionary trait loss elicited a significantly greater number of naïve biological elements than evolutionary trait gain tasks in all contexts, including: within species comparisons, between species comparisons, animal prompts, and plant prompts. Tasks involving between species evolutionary comparisons, regardless of gain or loss, animal or plant, always produced significantly more naïve biological explanatory elements than within species comparisons. For items prompting explanation of trait gain, the use of the core concepts of natural selection were not influenced by the hierarchical level of the task (within or between species). Explanations of trait gain were also the least sensitive to scale and context. Core concepts of natural selection were always deployed less frequently in cases of evolutionary trait loss (within and between species, in animals and plants). We discuss a series of implications of these findings for curriculum, instruction, and assessment. © 2010 Wiley Periodicals, Inc., Inc. J Res Sci Teach 48: 237–256, 2011     

Preference effects on acquisition and retention of concurrent discriminations by rhesus monkeys

Ten rhesus monkeys were trained on five tasks, each of which consisted of eight concurrently presented object discrimination problems. Sequences of presentation were devised to allow one, two, or three new tasks to intervene between acquisition and retention tests or to provide a 30-day period of no testing. Equivalent and proficient performances were obtained in all retention tests, and no relationship was observed between retention and the initial preference characteristics of various objects. Object pReferences did produce significant influences upon acquisition, but these effects were not as pronounced in early tasks as in later ones. An additional retention test provided support for the contention that monkeys do not necessarily process information about specific object pair discriminations. Rather, they appeared to retain a list of previously rewarded objects even when object pairings were different from those provided during acquisition. Concurrent discriminations involving many distinct objects were resistant to interference and independent of preference characteristics over long retention periods.     

Stimulus control in multiple temporal discriminations

In multiple fixed interval (FI) schedules, rats are trained to discriminate different FIs that are signaled by different stimuli. After extensive training, the different stimuli often acquire control over performance, observed by an earlier increase in responding for stimuli that signal shorter FIs, as compared with stimuli that signal longer FIs. The order in which the different FIs are trained, either intermixed across cycles or in blocks of several cycles, may seem irrelevant given that average performance at asymptote may be similar. In this study, rats were trained in two procedures with multiple FIs presented intermixed within sessions or in blocks of one interval per session. Similar performance was observed at asymptote, but an inspection of early cycles in each session revealed that different stimuli acquired control over performance only when trained intermixed within each session. Although the stimuli reliably signaled the upcoming FI, when trained in successive blocks of 60 cycles, rats rapidly adjusted performance early in the sessions on the basis of the temporal aspects of the task, and not on the basis of the stimulus presented in the current cycle. These results are discussed in terms of overshadowing of the stimuli by temporal cues and in terms of conditions under which a stimulus acquires control over performance.     

Value transfer in concurrent-schedule discriminations by pigeons

When pigeons are trained on a discrete-trial simultaneous discrimination, some of the value associated with the positive stimulus appears to transfer to the negative stimulus (Zentall & Sherburne, 1994). Pigeons preferred a negative stimulus that had been discriminated from an always-positive stimulus (S+) over a negative stimulus that had been discriminated from a sometimes-positive stimulus (S±). A very different finding (suggestive of transitivity of preference or contrast) was reported by Belke (1992). On concurrent probe tests of stimuli associated with equal variable interval (VI) schedules but originally trained in alternative concurrent pairs (one with a richer schedule, the other with a poorer schedule—VI 20 sec vs. VI 40 sec and VI 40 sec vs. VI 80 sec), the stimulus originally paired with the poorer schedule was preferred. But Belke’s results may have been obtained because the pigeons had been trained to peck the VI 40 sec paired with the poorer schedule and they had been trained not to peck the VI 40 sec paired with the richer schedule. In the present experiment, we avoided this bias by training pigeons on two concurrent schedules in which the tested stimuli both had been associated with the poorer schedule of the pair [A(VI 20 sec) vs. B(VI 80 sec) and C(VI 40 sec) vs. D(VI 80 sec)]. Evidence for value transfer was demonstrated when on probe trials pigeons preferred B over D.     

Reducing the feature positive effect by alerting people to its existence

The feature-positive effect (FPE) is the phenomenon that learning organisms are better at detecting the association between two present stimuli than between the absence of one stimulus and the presence of the other. Although the FPE was first described 40 years ago, it remains an ill-studied and ill-understood bias. The aim of the present study was to test whether the FPE can be remedied by simply alerting individuals to the possibility that the solution to a given problem may lie in the diagnosticity of a stimulus being absent. The results indicated that the instructions given to participants can indeed reduce the FPE.     

Response modes in simultaneous and successive visual discriminations

Modes of responding in simultaneous and successive discrimination problems were investigated using a bidirectional transfer procedure. Rats receiving training on a simultaneous discrimination problem were transferred to successive discriminations. Rats trained on a successive problem were transferred to simultaneous problems. The transfer problems were either compatible or incompatible with the response mode present during training. The results suggest that a single response mode may underlie the solution of both simultaneous and successive discrimination problem.     

Improvements in interval time tracking and effects on reading achievement

This study examined the effect of improvements in timing/rhythmicity on students' reading achievement. 86 participants completed pre‐ and post‐test measures of reading achievement (i.e., Woodcock‐Johnson III, Comprehensive Test of Phonological Processing, Test of Word Reading Efficiency, and Test of Silent Word Reading Fluency). Students in the experimental group completed a 4‐week intervention designed to improve their timing/rhythmicity by reducing the latency in their response to a synchronized metronome beat, referred to as a synchronized metronome tapping (SMT) intervention. The results from this non‐academic intervention indicate the experimental group's post‐test scores on select measures of reading were significantly higher than the non‐treatment control group's scores at the end of 4 weeks. This paper provides a brief overview of domain‐general cognitive abilities believed effected by SMT interventions and provides a preliminary hypothesis to explain how this non‐academic intervention can demonstrate a statistically significant effect on students' reading achievement scores. © 2007 Wiley Periodicals, Inc. Psychol Schs 44: 849–863, 2007.