Stimulus mislocalization depends on spatial frequency.

It was previously reported that briefly presented peripheral stimuli are perceived closer to fixation than continuously presented stimuli at the same eccentricity; this effect has, however, not proved consistently replicable. In this study it was investigated whether the misperception of location might depend upon the spatial frequency content of the stimulus. Spatial-frequency-filtered vertical bars were displayed briefly and their locations were judged relative to continuously visible comparison spots. For monocular stimuli, a significant foveopetal mislocalization of the bar was obtained that increased in size as spatial frequency was lowered. Even larger mislocalizations were obtained for dichoptically presented horizontally disparate pairs of bars, and this effect also increased at low spatial frequencies. Possible underlying mechanisms are discussed, and spatial frequency is suggested to have been the confounding factor in previous studies.     

Mental scanning in auditory imagery for songs

Four experiments examined how people operate on memory representations of familiar songs. The tasks were similar to those used in studies of visual imagery. In one task, subjects saw a one-word lyric from a song and then saw a second lyric; then they had to say if the second lyric was from the same song as the first. In a second task, subjects mentally compared pitches of notes corresponding to song lyrics. In both tasks, reaction time increased as a function of the distance in beats between the two lyrics in the actual song, and in some conditions reaction time increased with the starting beat of the earlier lyric. Imagery instructions modified the main results somewhat in the first task, but not in the second, much harder task. The results suggest that song representations have temporal-like characteristics.     

Word-association responses to time-altered stimuli by schizophrenic adults

This research addressed the relationship between the speed of presentation of stimuli through the auditory and visual modalities and the number of syntagmatic and paradigmatic word-association responses of 49 chronic undifferentiated schizophrenic adults. In word-association tests administered to subjects stimuli were balanced for frequency of occurrence in written English language (frequent, infrequent), word length (long, short), abstraction level (low, medium, high), and part of speech (noun, verb, adjective). The words were presented auditorily at normal speed (equivalent to 10 phonemes per second) and at half speed (equivalent to 5 phonemes per second) speech. Words were also presented visually, using a tachistoscope, at extended fixation speed (equivalent to 1,000 msec.) and at sweep speed (equivalent to 10 msec.). More paradigmatic responses occurred on word stimuli if nouns, long, and frequently occurring presented auditorily; and if concrete, nouns, and presented slowly and visually. Results were compared to previously reported data for aphasic and normal adults, and differentiating features and clinical implications were discussed.     

Taken by surprise: The paradox of the surprise test revisited

A teacher announced to his pupils that on exactly one of the days of the following school week (Monday through Friday) he would give them a test. But it would be a surprise test; on the evening before the test they would not know that the test would take place the next day. One of the brighter students in the class then argued that the teacher could never give them the test. It can't be Friday, she said, since in that case we'll expect it on Thurday evening. But then it can't be Thursday, since having already eliminated Friday we'll know Wednesday evening that it has to be Thursday. And by similar reasoning we can also eliminate Wednesday, Tuesday, and Monday. So there can't be a test!The students were somewhat baffled by the situation. The teacher was well-known to be truthful, so if he said there would be a test, then it was safe to assume that there would be one. On the other hand, he also said that the test would be a surprise. But it seemed that whenever he gave the test, it wouldn't be a surprise.Well, the teacher gave the test on Tuesday, and, sure enough, the students were surprised.     

Neonate plains garter snakes (Thamnophis radix) are attracted to conspecific skin extracts

Several species of snakes aggregate in areas previously marked by conspecifics. However, species differences and sources of such chemical signals have received little attention. Methylene chloride-soluble substances from shed epidermis of adult plains garter snakes attracted neonate conspecifics, whereas similar extracts from a congener and a viperid did not. The functional significance of such conspecific aggregation may relate to location of hibernacula, foraging areas, osmoregulation, or predation avoidance.     

Memory for the absolute pitch of familiar songs

Four experiments were conducted to examine the ability of people without "perfect pitch" to retain the absolute pitch of familiar tunes. In Experiment 1, participants imagined given tunes, and then hummed their first notes four times either between or within sessions. The variability of these productions was very low. Experiment 2 used a recognition paradigm, with results similar to those in Experiment 1 for musicians, but with some additional variability shown for unselected subjects. In Experiment 3, subjects rated the suitability of various pitches to start familiar tunes. Previously given preferred notes were rated high, as were notes three or four semitones distant from the preferred notes, but not notes one or two semitones distant. In Experiment 4, subjects mentally transformed the pitches of familiar tunes to the highest and lowest levels possible. These experiments suggest some retention of the absolute pitch of tunes despite a paucity of verbal or visual cues for the pitch.     

Evidence with uncertain likelihoods

An agent often has a number of hypotheses, and must choose among them based on observations, or outcomes of experiments. Each of these observations can be viewed as providing evidence for or against various hypotheses. All the attempts to formalize this intuition up to now have assumed that associated with each hypothesis h there is a likelihood function  μ _h , which is a probability measure that intuitively describes how likely each observation is, conditional on h being the correct hypothesis. We consider an extension of this framework where there is uncertainty as to which of a number of likelihood functions is appropriate, and discuss how one formal approach to defining evidence, which views evidence as a function from priors to posteriors, can be generalized to accommodate this uncertainty.