Perception of syllable-final stop consonants by 2-month-old infants

Previous research has shown that infants are capable of perceiving many phonetic distinctions between initial segments of syllables. The present study demonstrates that 2-month-old infants have the ability to distinguish syllables differing only in their final segments. Infants were found to be sensitive to place-of-articulation differences for stop consonants in final segments of both consonant-vowel-consonant (CVC) and vowel-consonant (VC) syllable pairs. Contrary to previous reports for older infants (Shvachkin, 1973), there was no indication that 2-month-olds have any more difficulty with contrasts of final-stop consonant:3 than they do with initial ones.     

A quantitative approach to the study of visual symmetry

An experiment was conducted to explore the quantitative relationship between "goodness" and the amount of symmetry in visual designs. Subjects arranged items in one, two, and three dimensions in an aesthetically pleasing manner. Each design was analyzed to determine its amount of symmetry, and the percent of subjects who created designs having each possible degree of asymmetry was calculated. Perfect symmetry was the most common condition for all three dimensions. Moreover, the goodness of patterns was inversely related to the quantitative degree of asymmetry.     

A dual task response modality effect: Support for multiprocessor models of attention

In Experiment I two groups of 11 men performed a continuous visual input/manual output task simultaneously with a two-choice tone identification task. One group responded vocally to the tones; one group responded with the hand not involved in the continuous tracking task. In either perceptual or stimulus uncertainty terms the two combinations were identical; the only difference between them was the modality of the two-choice responses. The continuous task was performed significantly worse when the two-choice responses were manual. The probability of response production on the continuous task was affected by the production of manual responses but not by the production of vocal responses. It was concluded that although the two manual responses were produced by a single limited capacity process, the manual and vocal responses were produced by independent processes. In Experiment II the same manual tracking task was combined with a mental arithmetic task at two levels of difficulty. Tracking performance was independent of the difficulty of the arithmetic task. These results support a multi-processor approach to attention as opposed to single channel models. Results of dual task studies which have used only one pair of response modalities are re-examined in the light of the response modality effect found in Experiment I.     

Fixed-interval punishment of running in hamsters

Four hamsters received brief electric shocks contingent upon running in a wheel. The fixed interval between shocks was varied systematically from 0 to 60 sec. Time spent running was directly related to the length of the fixed interval, while running speed remained roughly constant. Running depended on the fixed interval between shocks in the same way as bar-pressing maintained by food reinforcement, despite the fact that running was not established with nor maintained by explicit reinforcement.