The acquisition of an artificial category by pigeons

This article investigates the ability of pigeons to discriminate between artificial categories composed of patterns constructed from three adjacent bars. In three experiments, using autoshaping, the patterns signalled either the presence or the absence of food, and the categories were determined by the average height of the bars. The subjects were able to discriminate between these categories, and the results from generalization tests with novel patterns provide some indication of the way in which this success is achieved. It seems the discrimination does not involve the formation of a prototype that represents the average of the training patterns. Instead, the results suggest that the discrimination depends upon the formation of multiple associations, either between features of the various patterns and reinforcement, or between individual members of the category and reinforcement.     

The acquisition of homonymy

The growth in children's ability to perform the task of separating the sounds of words from their meanings was investigated by asking children between 3;3 and 6;3 to select homonyms from pictures. The results show a growth in ability with age, with a jump at 4;4. An investigation of the developmental changes in the strategies employed shows that the task is cognitively complex. Performance in the younger children is more hampered by a resource-limited inability to cope with many cognitive factors all at once than by lack of ability to do the linguistic aspects of the task. These cognitive factors include access to vocabulary, rehearsal of intermediate results, and implementation of a search strategy.     

The distributed learning effect for children's acquisition of an abstract syntactic construction

In many cognitive domains, learning is more effective when exemplars are distributed over a number of sessions than when they are all presented within one session. The present study investigated this distributed learning effect with respect to English-speaking children's acquisition of a complex grammatical construction. Forty-eight children aged 3;6–5;10 (Experiment 1) and 72 children aged 4;0–5;0 (Experiment 2) were given 10 exposures to the construction all in one session (massed), or on a schedule of two trials per day for 5 days (distributed-pairs), or one trial per day for 10 days (distributed). Children in both the distributed-pairs and distributed conditions learnt the construction better than children in the massed condition, as evidenced by productive use of this construction with a verb that had not been presented during training. Methodological and theoretical implications of this finding are discussed, with particular reference to single-process accounts of language acquisition.     

Songs as an aid for language acquisition

In previous research, Saffran and colleagues [Saffran, J. R., Aslin, R. N., & Newport, E. L. (1996). Statistical learning by 8-month-old infants. Science, 274, 1926-1928; Saffran, J. R., Newport, E. L., & Aslin, R. N. (1996). Word segmentation: The role of distributional cues. Journal of Memory and Language, 35, 606-621.] have shown that adults and infants can use the statistical properties of syllable sequences to extract words from continuous speech. They also showed that a similar learning mechanism operates with musical stimuli [Saffran, J. R., Johnson, R. E. K., Aslin, N., & Newport, E. L. (1999). Abstract Statistical learning of tone sequences by human infants and adults. Cognition, 70, 27-52.]. In this work we combined linguistic and musical information and we compared language learning based on speech sequences to language learning based on sung sequences. We hypothesized that, compared to speech sequences, a consistent mapping of linguistic and musical information would enhance learning. Results confirmed the hypothesis showing a strong learning facilitation of song compared to speech. Most importantly, the present results show that learning a new language, especially in the first learning phase wherein one needs to segment new words, may largely benefit of the motivational and structuring properties of music in song.     

The acquisition of behavioral chains

The present investigation was designed to study some conditions which facilitate the acquisition of behavioral chains by young children. Three experiments were performed. In Expt I subjects were required to respond overtly to the internal components of the chain. In Expt II an aversive contingency was imposed following errors. In Expt III instructions were added at the beginning of training. The results supported the following conclusions: (a) Requiring subjects to mark and name the correct stimuli on each trial increased the accuracy of performance; (b) introducing time-out contingent on incorrect responses depressed the error rate; and (c) adding instructions concerning a pending change in the experimental task resulted in a lower error rate following withdrawal of the instructional stimuli.     

The acquisition of conditioned responding

This report analyzes the acquisition of conditioned responses in rats trained in a magazine approach paradigm. Following the suggestion by Gallistel, Fairhurst, and Balsam (2004), Weibull functions were fitted to the trial-by-trial response rates of individual rats. These showed that the emergence of responding was often delayed, after which the response rate would increase relatively gradually across trials. The fit of the Weibull function to the behavioral data of each rat was equaled by that of a cumulative exponential function incorporating a response threshold. Thus, the growth in conditioning strength on each trial can be modeled by the derivative of the exponential--a difference term of the form used in many models of associative learning (e.g., Rescorla & Wagner, 1972). Further analyses, comparing the acquisition of responding with a continuously reinforced stimulus (CRf) and a partially reinforced stimulus (PRf), provided further evidence in support of the difference term. In conclusion, the results are consistent with conventional models that describe learning as the growth of associative strength, incremented on each trial by an error-correction process.     

The acquisition of odour qualities

Odours can evoke a large range of qualities. Some of these qualities (e.g., sweetness) appear to be acquired through simultaneously experiencing odours mixed with tastes. Acquisition might also occur when two odours are experienced as a mixture. In this case mixture components might acquire each other's qualities. This was tested in two experiments. In the first, subjects repeatedly sniffed two odour mixtures (either AX, BY or AY, BX). Odours mixed with A acquired A's properties and were judged more similar to A than to B. Odours mixed with B were not clearly discriminable. The second experiment used a similar approach except that Odour B was replaced. Subjects now smelled either AX, CY or AY, CX. All components were discriminable. Odours mixed with A acquired A's properties and were judged more similar to A than to C. Although odours mixed with C did not acquire C's qualities due to a confusion of quality terms, odours previously mixed with C were judged as more similar to C than to A. Evidence of other quality exchanges were also obtained. These results suggest that pure odour qualities can be learnt and lend support to William James's (1890) notion of the acquired equivalence/distinctiveness of cues.     

The acquisition of observing.

Pigeons were exposed to stimuli correlated with the presence or absence of a variable-interval 60-second schedule of reinforcement only while they depressed a crossbar or "perch." In the first experiment, the stimuli were different tilts of a line displayed on the key. When the difference in brightness between the line and the background (salience) was maximal, seven of eight birds acquired the discrimination, but when the difference was reduced by 50%, only one succeeded. In the second experiment, wavelength of chamber illumination served as the relevant dimension. Neither experiment showed a large effect attributable to the magnitude of the difference (disparity) between the positive and the negative stimulus. Individual differences in time spent observing were positively correlated with level of discrimination in the presence of the stimuli. All birds produced the positive stimulus for a greater proportion of the available time than they did the negative stimulus. This may be the mechanism that provides selective reinforcement of observing. Finally, the formation of a discrimination was analyzed in terms of changes in the proportion of time spent in contact with the discriminative stimuli.     

Rapid acquisition of an auditory localization discrimination by rats

Acquisition of a sound localization discrimination by rats was investigated. Two loudspeakers were located outside an experimental enclosure containing two levers and a dipper feeder. In the same-side condition, responses on the lever nearest the sound-producing speaker were reinforced. Animals in this condition acquired the discrimination rapidly, generally within the first session. In the opposite-side condition, responses on the lever furthest from the sound-producing speaker were reinforced. Acquisition for animals in this condition began below the chance level (50% correct responses) and took on the order of 10 sessions to approach the final, high level. The course of acquisition in both cases appeared to depend upon an initial tendency of rats to respond on the lever nearest the source of sound in this situation. The rise-decay time of the 4-kHz tone burst signal clearly affected the performance level reached. It did not, however, affect the rate at which the discrimination was acquired.     

The conditioned reinforcement of repeated acquisition

Three monkeys were trained to emit a chain of three responses on three separate levers in a set of six levers to obtain food. The chain producing food (correct chain) was changed each day. During a trial, a press on any lever produced a feedback stimulus; a press on a correct lever produced an additional distinctive stimulus; the third correct press produced a food pellet. Test sessions in which either the food or the distinctive stimuli were removed were interspersed with baseline sessions. In tests without food presentations, the subjects acquired the correct chain rapidly, with a level of accuracy comparable to baseline. Removing the distintive stimuli for either the first or second member of the correct chain greatly retarded acquisition of that member of the chain. Removing all distinctive stimuli often reduced accuracy throughout the chain to chance level, even though food was presented following each correct chain. These results were interpreted as evidence that the distinctive stimuli presented after correct responses functioned as conditioned reinforcers. Reductions in accuracy following an omitted distinctive stimulus indicated that they were also discriminative stimuli for correct responding in their presence.     

The repeated acquisition of behavioral chains

Monkeys were trained with food reinforcement in a chamber containing four groups of three levers. For each session the monkey's task was to learn a new four-response chain by pressing the correct lever in each group. A stable pattern of learning resulted, and the number of errors reached a steady state from session to session. The technique was then used to determine how various durations of timeouts, following errors, affected the acquisition of new chains. With no timeout, the monkeys made a great many errors, due in large part to superstitious responses within the reinforced chain. Timeout durations ranging from 1 sec to 4 min reduced the number of errors substantially. A second experiment investigated the effects upon acquisition errors of presenting a single light (an “instruction” stimulus) over the correct lever. When this light did not influence the monkeys' responses to the three alternatives, the chains were learned as without it. When the light did control responding, the monkey pressed the appropriate sequence of levers but did not learn the sequence. Thus, when the light was removed, the monkey performed as if learning that sequence for the first time.     

The acquisition of prenominal modifier sequences

This paper presents a study of children's interpretations of prenominal modifier sequences like the one in ‘the second green ball’. In such phrases the modifier ‘second’ has scope over the rest of the phrase. It is shown that children misinterpret these phrases in such a way that it appears that they give ‘second’ scope only over the head noun of the phrase. A series of six experiments, all designed to test various hypotheses about the motivating factors behind this misinterpretation is described. Experiments 1 and 2 constitute a replication and extension of the work in this area originally done by Roeper (1972). Experiment 3 tests a set of hypotheses about the influence of certain syntactic variables in conditioning the children's misinterpretations. Experiment 4 is an attempt to check an hypothesis about the semantic complexity of phrases like ‘the second green ball’. Experiments 5 and 6 test the children's sensitivity to ordering constraints in different kinds of prenominal modifier sequences. The results are presented in Section 3 and discussed in Section 4. It is argued that the children's misinterpretations of the phrases come about because of their tendency to be conservative about the amount of hierarchically organized structure they will postulate in the absence of evidence that such structure is needed.     

The acquisition of abstract letter codes

A modification of Posner's letter-matching paradigm proposed by Beller (1971) was employed to study the development of abstract visual and name codes for letters. Second-, fourth-, and sixth-grade students (ages 8, 10, and 12 years, respectively) were presented in advance one of a pair of to-be-matched letters. Case agreement (upper- and lowercase) between the prime letter and the letter pair was manipulated to differentiate facilitation based on concrete features of the stimulus letter from that based on the letter's abstract visual code. For physical matches second graders showed greater facilitation from same-case primes than from different-case primes, whereas sixth graders benefited equally from both types of prime. For same-name and different conditions, no qualitative developmental differences were revealed as all subjects benefited from letter primes irrespective of case agreement. The acquisition and utilization of abstract visual codes for letters are a later acquisition than name codes, which were clearly operative at the lowest grade level in the present experiment.