Equivalence class establishment, expansion, and modification in preschool children

Preschool children were taught four two-choice match-to-sample conditional discriminations with 10 arbitrary visual stimuli. For 6 participants, 2 of the 10 stimuli served as the sample, or conditional, stimuli in all discriminations. For 5 additional participants, the same pair of stimuli served as the discriminative, or comparison, stimuli in all discriminations. Equivalence classes were established with more participants in the latter group, replicating prior research with participants with retardation. Four participants, in whom equivalence classes were established and who were available for further participation, were exposed to new conditional discriminations without trial-by-trial feedback and involving some novel and some familiar stimuli. Consistent conditional responding was observed, and tests for inclusion of the novel stimuli in the original classes showed class expansion. Training to reverse the unreinforced conditional performances produced a reversal of class membership in 3 of 4 participants, an outcome not consistent with other studies. The results are discussed with respect to the interaction of class structure and size.     

A discrimination analysis of training-structure effects on stimulus equivalence outcomes.

Experiments designed to establish stimulus equivalence classes frequently produce differential outcomes that may be attributable to training structure, defined as the order and arrangement of baseline conditional discrimination training trials. Several possible explanations for these differences have been suggested. Here we develop a hypothesis based on an analysis of the simple simultaneous and successive discriminations embedded in conditional discrimination training and testing within each of the training structures that are typically used in stimulus equivalence experiments. Our analysis shows that only the comparison-as-node (many-to-one) structure presents all the simple discriminations in training that are subsequently required for consistently positive outcomes on all tests for the properties of equivalence. The sample-as-node (one-to-many) training structure does not present all the simple discriminations required for positive outcomes on either the symmetry or combined transitivity and symmetry (equivalence) tests. The linear-series training structure presents all the simple discriminations required for consistently positive outcomes on tests for symmetry, but not for symmetry and transitivity combined (equivalence) or transitivity alone. Further, the difference in the number of simple discriminations presented in comparison-as-node training versus the other training structures is larger when the intended class size is greater than three or the number of classes is larger than two. We discuss the relevance of this analysis to interpretations of stimulus equivalence research, as well as some methodological and theoretical implications.     

Infants’ coding of location in continuous space

The ability to code location in continuous space is fundamental to spatial behavior. Existing evidence indicates a robust ability for such coding by 12 months, but systematic evidence on earlier origins is lacking. A series of studies investigated 5-month-olds’ ability to code the location of an object hidden in a sandbox, using a looking-time paradigm. In Experiment 1, after familiarization with a hiding-and-finding sequence at one location, infants looked longer at an object being disclosed from a location 12 inches (30 cm) away than at an object emerging from the hiding location, showing they were able to code location in continuous space. In Experiment 2, infants reacted with greater looking when objects emerged from locations 8 inches (20 cm) away from the hiding location, showing that location coding was more finely grained than could be inferred based on the first study. In Experiment 3, infants were familiarized with an object shown in hiding-and-finding sequences at two different locations. Infants looked longer at objects emerging 12 inches (30 cm) away from the most recent hiding location than to emergence from the other location, showing that infants could code location even when events had previously occurred at each location. In Experiment 4, after familiarization with two objects with different shapes, colors, and sounding characteristics, shown in hiding-and-finding sequences in two locations, infants reacted to location violations as they had in Experiment 3. However, they did not react to object violations, that is, events in which the wrong object emerged from a hiding location. Experiment 5 also found no effect of object violation, even when the infants initially saw the two objects side by side. Spatiotemporal characteristics may play a more central role in early object individuation than they do later, although further study is required.     

Infant responses to adult happy and sad vocal and facial expressions during face-to-face interactions

We examined 5-month-olds’ responses to adult facial versus vocal displays of happy and sad expressions during face-to-face social interactions in three experiments. Infants interacted with adults in either happy-sad-happy or happy-happy-happy sequences. Across experiments, either facial expressions were present while presence/absence of vocal expressions was manipulated or visual access to facial expressions was blocked but vocal expressions were present throughout. Both visual attention and infant affect were recorded. Although infants looked more when vocal expressions were present, they smiled significantly more to happy than to sad facial expressions regardless of presence or absence of the voice. In contrast, infants showed no evidence of differential responding to voices when faces were obscured; their smiling and visual attention simply declined over time. These results extend findings from non-social contexts to social interactions and also indicate that infants may require facial expressions to be present to discriminate among adult vocal expressions of affect.     

Influence of Social Perception and Social Monitoring on Structural Priming

Although structural priming has been considered to be an independent cognitive process, recent evidence suggests that structural priming is modulated by sociocognitive factors such as social perception; speakers are more likely to mimic the sentence structure of a socially desirable interlocutor than the structure of a less desirable interlocutor. This study aims to further address the role of sociocognitive factors in language use by investigating how individual differences in social perception and tendency to align with others (i.e., social monitoring) modulate same‐verb structural priming. In particular, we investigate how likely students are to repeat a sentence structure of a teacher depending on their perception of the teacher and their social monitoring tendency. Our results demonstrate that students’ tendency to imitate a sentence structure of the teacher is positively influenced by their perception of the teacher but negatively by social monitoring. We suggest that the effects may be accounted for in terms of their influence on attention and memory encoding.     

Are Words Easier to Learn From Infant‐ Than Adult‐Directed Speech? A Quantitative Corpus‐Based Investigation

We investigate whether infant‐directed speech (IDS) could facilitate word form learning when compared to adult‐directed speech (ADS). To study this, we examine the distribution of word forms at two levels, acoustic and phonological, using a large database of spontaneous speech in Japanese. At the acoustic level we show that, as has been documented before for phonemes, the realizations of words are more variable and less discriminable in IDS than in ADS. At the phonological level, we find an effect in the opposite direction: The IDS lexicon contains more distinctive words (such as onomatopoeias) than the ADS counterpart. Combining the acoustic and phonological metrics together in a global discriminability score reveals that the bigger separation of lexical categories in the phonological space does not compensate for the opposite effect observed at the acoustic level. As a result, IDS word forms are still globally less discriminable than ADS word forms, even though the effect is numerically small. We discuss the implication of these findings for the view that the functional role of IDS is to improve language learnability.     

Perceiving a story outside of conscious awareness: When we infer narrative attributes from subliminal sequential stimuli

Perceiving a story behind successive movements plays an important role in our lives. From a general perspective, such higher mental activity would seem to depend on conscious processes. Using a subliminal priming paradigm, we demonstrated that such story perception occurs without conscious awareness. In the experiments, participants were subliminally presented with sequential pictures that represented a story in which one geometrical figure was chased by the other figure, and in which one fictitious character defeated the other character in a tug-of-war. Although the participants could not report having seen the pictures, their automatic mental associations (i.e., associations that are activated unintentionally, difficult to control, and not necessarily endorsed at a conscious level) were shifted to line up with the story. The results suggest that story perception operates outside of conscious awareness. Implications for research on the unconscious were also briefly discussed.     

Individual differences in vulnerability to subjective time distortion1

Time duration is perceived to be longer when accompanied by dynamic sensory stimulation than when accompanied by static stimulation. This distortion of time perception is thought to be due to the acceleration of an internal pacemaker that has been assumed to be the main component of temporal judgments. In order to investigate whether the function of the internal pacemaker is modality dependent or independent, we examined the correlation of visual flicker and auditory flutter effects on a temporal production task. While seeing a 10‐Hz visual flicker or hearing a 10‐Hz auditory flutter, participants estimated a duration of 2500 ms as accurately as possible by pressing a button. The results showed a significant within‐individual correlation between the time distortion due to visual flicker and that due to auditory flutter. Additionally, we found that time distortion due to auditory flutter tended to be larger in female participants than in male participants. These results suggest that the mechanisms underlying subjective time dilation are similar between vision and audition within individuals, but that they vary across individuals.     

Detection of a change in photorealism1

The perceived degree of photorealism is interpreted as reflecting the artificialness or naturalness of images. Natural images (real‐scene photographs) are images with high degrees of naturalness, while artificial images (e.g., paintings) are images with low degrees of naturalness. Alternatively, natural images are images with low degrees of artificialness, while artificial images are images with high degrees of artificialness. We attempted to disambiguate these two interpretations of the perception of photorealism by using a change‐blindness paradigm. Participants observed an image sequence showing a gradual transformation from a natural image to an artificial image or vice versa, and reported changes they noticed. More participants reported noticing changes in photorealism for the natural‐to‐artificial transformations than for the opposite transformations. This asymmetry indicates that disappearing naturalness was detected more readily than emerging naturalness, or alternatively, emerging artificialness was detected more readily than disappearing artificialness. The results for the control conditions showed that the emergence of visual information was detected more readily than the disappearance. These results suggest that the perception of photorealism should be considered as the perception of artificialness.     

Acquisition of social referencing via discrimination training in infants

This experiment investigated social referencing as a form of discriminative learning in which maternal facial expressions signaled the consequences of the infant's behavior in an ambiguous context. Eleven 4- and 5-month-old infants and their mothers participated in a discrimination-training procedure using an ABAB design. Different consequences followed infants' reaching toward an unfamiliar object depending on the particular maternal facial expression. During the training phases, a joyful facial expression signaled positive reinforcement for the infant reaching for an ambiguous object, whereas a fearful expression signaled aversive stimulation for the same response. Baseline and extinction conditions were implemented as controls. Mothers' expressions acquired control over infants' approach behavior for all participants. All participants ceased to show discriminated responding during the extinction phase. The results suggest that 4- and 5-month-old infants can learn social referencing via discrimination training.