The measurement of the lateralization of narrow bands of noise using an acoustic pointing paradigm: the effect of sound-pressure level

The effects of varying interaural time delay (ITD) and interaural intensity difference (IID) were measured in normal-hearing subjects as a function of eleven frequencies and at sound-pressure levels (SPL) from 60 to 90 dB SPL and at 25-dB sensation level. Using an "acoustic" pointing paradigm, the IID of a 500-Hz narrow-band (100 Hz) noise (the "pointer") was varied by the subject to coincide with that of a "target" ITD stimulus. ITDs of 0, +/- 200, and +/- 400 microseconds were obtained through total waveform delays of narrow-band noise (NBN), including envelope and fine structure. The results of this experiment confirm the traditional view of binaural hearing for like stimuli: There is little perceived displacement away from 0 IID at frequencies of 1250 Hz and above. In the low frequencies, subjects required IIDs greater than the expected 10 dB to perceive a fully lateralized image, and they varied in the maximum value of IID that they required, regardless of frequency. Our subjects did not always perceive the intracranial locations of ITD targets symmetrically: When the signal was delayed to one ear, the resultant matching IID was often different in magnitude than for the same ITD target delayed to the opposite ear for the identical frequency. The results of two subjects suggested that people with asymmetric normal hearing have adapted to their asymmetry for lateralization tasks: The subjects were found to lateralize toward the ear with the greater SPL stimulus, regardless of the ear to which the signal was delayed, when signals of equal SL were presented, and toward the leading ear when signals of equal SPL were presented (unequal SL). Increasing the presentation levels above 60 dB SPL had an effect on the perception of high-frequency ITD targets: As the intensity level increased, the slopes of the IID versus ITD functions increased indicating better discrimination of ITD. This study is in agreement with other studies in providing strong evidence of individual differences in lateralization experiments. These individual differences might be attributable to differential sensitivity to ambiguous time stimulus cues, differential task sensitivity, age effects, threshold asymmetries, or criterion variability.     

How the owl resolves auditory coding ambiguity

The barn owl (Tyto alba) uses interaural time difference (ITD) cues to localize sounds in the horizontal plane. Low-order binaural auditory neurons with sharp frequency tuning act as narrow-band coincidence detectors; such neurons respond equally well to sounds with a particular ITD and its phase equivalents and are said to be phase ambiguous. Higher-order neurons with broad frequency tuning are unambiguously selective for single ITDs in response to broad-band sounds and show little or no response to phase equivalents. Selectivity for single ITDs is thought to arise from the convergence of parallel, narrow-band frequency channels that originate in the cochlea. ITD tuning to variable bandwidth stimuli was measured in higher-order neurons of the owl's inferior colliculus to examine the rules that govern the relationship between frequency channel convergence and the resolution of phase ambiguity. Ambiguity decreased as stimulus bandwidth increased, reaching a minimum at 2-3 kHz. Two independent mechanisms appear to contribute to the elimination of ambiguity: one suppressive and one facilitative. The integration of information carried by parallel, distributed processing channels is a common theme of sensory processing that spans both modality and species boundaries. The principles underlying the resolution of phase ambiguity and frequency channel convergence in the owl may have implications for other sensory systems, such as electrolocation in electric fish and the computation of binocular disparity in the avian and mammalian visual systems.     

Sensitivity to interaural time differences in the medial superior olive of a small mammal, the Mexican free-tailed bat

Neurons in the medial superior olive (MSO) are thought to encode interaural time differences (ITDs), the main binaural cues used for localizing low-frequency sounds in the horizontal plane. The underlying mechanism is supposed to rely on a coincidence of excitatory inputs from the two ears that are phase-locked to either the stimulus frequency or the stimulus envelope. Extracellular recordings from MSO neurons in several mammals conform with this theory. However, there are two aspects that remain puzzling. The first concerns the role of the MSO in small mammals that have relatively poor low-frequency hearing and whose heads generate only very small ITDs. The second puzzling aspect of the scenario concerns the role of the prominent binaural inhibitory inputs to MSO neurons. We examined these two unresolved issues by recording from MSO cells in the Mexican free-tailed bat. Using sinusoidally amplitude-modulated tones, we found that the ITD sensitivities of many MSO cells in the bat were remarkably similar to those reported for larger mammals. Our data also indicate an important role for inhibition in sharpening ITD sensitivity and increasing the dynamic range of ITD functions. A simple model of ITD coding based on the timing of multiple inputs is proposed. Additionally, our data suggest that ITD coding is a by-product of a neuronal circuit that processes the temporal structure of sounds. Because of the free-tailed bat's small head size, ITD coding is most likely not the major function of the MSO in this small mammal and probably other small mammals.     

Auditory objects of attention: The role of interaural time differences.

The role of interaural time difference (ITD) in perceptual grouping and selective attention was explored in 3 experiments. Experiment 1 showed that listeners can use small differences in ITD between 2 sentences to say which of 2 short, constant target words was part of the attended sentence, in the absence of talker or fundamental frequency differences. Experiments 2 and 3 showed that listeners do not explicitly track components that share a common ITD. Their inability to segregate a harmonic from a target vowel by a difference in ITD was not substantially changed by the vowel being placed in a sentence context, where the sentence shared the same ITD as the rest of the vowel. The results indicate that in following a particular auditory sound source over time, listeners attend to perceived auditory objects at particular azimuthal positions rather than attend explicitly to those frequency components that share a common ITD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Shifting and focusing auditory spatial attention.

Auditory spatial attention was investigated by manipulating spatial and temporal relations between an auditory spatial cue and an auditory target. The principal findings were that performance improved as time available to shift attention to a cued spatial position increased, accurate spatial cues facilitated performance more than inaccurate cues, performance was virtually identical for shifts of attention ranging from 0° and 180°, and performance declined as the distance of an unexpected target from a cued spatial location increased. The experiments provided evidence that auditory attention may be allocated to a specific location in response to an auditory spatial cue and that the time required to shift attention does not appear to depend on the distance of the shift. Furthermore, the findings suggest that the spatial distribution of auditory attention may be described most accurately by a gradient model in which attentional resources decline gradually with distance from a focal point. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The conditional binomial test revisited for clinical trials

Even when the speaker, context, and speaking style are held fixed, the physical properties of naturally spoken utterances of the same speech sound vary considerably. This variability imposes limits on our ability to distinguish between different speech sounds. We present a conceptual framework for relating the ability to distinguish between speech sounds in single-token experiments (in which each speech sound is represented by a single wave form) to resolution in multiple-token experiments. Experimental results indicate that this ability is substantially reduced by an increase in the number of tokens from 1 to 4, but that there is little further reduction when the number of tokens increases to 16. Furthermore, although there is little relation between the ability to distinguish between a given pair of tokens in the multiple- and the 1-token experiments, there is a modest correlation between the ability to distinguish specific vowel tokens in the 4- and 16-token experiments. These results suggest that while listeners use a multiplicity of cues to distinguish between single tokens of a pair of vowel sounds, so that performance is highly variable both across tokens and listeners, they use a smaller set when distinguishing between populations of naturally produced vowel tokens, so that variability is reduced. The effectiveness of the cues used in the latter case is limited more by internal noise than by the variability of the cues themselves.     

Change deafness and the organizational properties of sounds.

Change blindness, or the failure to detect (often large) changes to visual scenes, has been demonstrated in a variety of different situations. Failures to detect auditory changes are far less studied, and thus little is known about the nature of change deafness. Five experiments were conducted to explore the processes involved in change deafness by measuring explicit change detection as well as auditory object encoding. The experiments revealed that considerable change deafness occurs, even though auditory objects are encoded quite well. Familiarity with the objects did not affect detection or recognition performance. Whereas spatial location was not an effective cue, fundamental frequency and the periodicity/aperiodicity of the sounds provided important cues for the change-detection task. Implications for the mechanisms responsible for change deafness and auditory sound organization are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of visual and body movement information in infant search.

Three experiments investigated the use of visual input and body movement input arising from movement through the world on spatial orientation. Infants between 9.5 and 18 months participated in a search task in which they searched for a toy hidden in 1 of 2 containers. Prior to beginning search, either the infants or the containers were rotated 180*; these rotations occurred in a lit or dark environment. These experiments were distinguished by the environmental cues for object location; Experiment 1 used a position cue, Experiment 2 a color cue, and Experiment 3 both position and color cues. Accuracy was better in Experiments 2 and 3 than in Experiment 1. All studies found that search was best after infant movement in the light; all other conditions led to equivalently worse performance. These results are discussed relative to a theoretical characterization of spatial coding focusing on the uses of spatial information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial guidance of choice behavior in the radial-arm maze.

In 6 experiments, the performance of male rats in a 12-arm radial maze was examined. The focus of study was the extent to which the spatial location of individual baited maze arms was determined before the rat was exposed to the extramaze visual cues corresponding to the arm, and thereby guided the rat toward the location of baited arms. Such spatial guidance of choice behavior implies a spatially organized cognitive representation of maze arms (i.e., a cognitive map). A higher level of spatial guidance was found when visual access to extramaze cues was restricted than when it was unrestricted. There was no evidence of a difference between the level of spatial guidance in the context of working memory performance and reference memory performance. Some evidence that intramaze cues contributed to microchoice guidance was found. However, spatial guidance, under at least some conditions, is best explained in terms of cognitive mapping. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sound localization in the median sagittal plane by listeners with presbyacusis

In Experiment 1, a group of listeners with substantial hearing loss due to presbyacusis and a group of listeners with normal hearing were given three localization tests: a frontal plane test in which they judged whether sounds came from the left, overhead, or the right; a sagittal plane test in which they judged whether sounds came from directly in front, overhead, or behind; and an elevation test in which they judged the vertical position of sounds coming from in front. The two groups performed similarly on the frontal plane test, which chiefly depended upon their ability to use binaural localization cues. They performed differently on the sagittal plane and elevation tests, for which the predominant localization cues were spectral. The listeners with presbyacusis were substantially less accurate than those with normal hearing in both of these instances. They had particular difficulty judging source elevation, rarely scoring much above chance. Follow-up testing of a group of subjects in the early stages of presbyacusis showed localization performance that was intermediate to the other two groups, but far more like that of the normal-hearing listeners. In Experiment 2, additional tests were run with the following conditions designed to encourage improved performance by listeners with presbyacusic hearing loss: (1) filtering of stimuli to preclude masking of more informative high-frequency components by low frequencies; (2) simplification of the elevation test and greater spatial separation of its loudspeaker sources; and (3) use of hearing aids. Conditions 1 and 2 had no appreciable effect on performance; condition 3 significantly improved presbyacusic listeners' ability to localize in the sagittal plane, particularly when sounds came from the front.     

Picture cues and exhaustive search facilitate very young children's memory for location.

Conducted 3 experiments to examine the effects of picture cues and exhaustive search on very young children's memory for the location of hidden objects. In Exp I, 64 2-yr-olds' performance was examined with control and exhaustive search procedures in spatial-only and spatial- and picture-cue conditions. In Exp II, 32 2-yr-olds' performance with the same 2 search procedures was examined in a cue condition that eliminated spatial information. In Exp III, 64 2- and 3-yr-olds' performance with the control and exhaustive search procedures was examined in 2 array conditions that also eliminated spatial information. All experiments confirmed that even 2-yr-olds use picture cues to encode and search for the location of hidden objects. It was also found that while 2-yr-olds' delayed response performance was improved by exhaustive search procedures, this was not true for 3-yr-olds. Apparently, more complete search strategies contribute to the developmental change in young children's localization performance. (10 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Separate mechanisms recruited by exogenous and endogenous spatial cues: Evidence from a spatial Stroop paradigm.

The present experiments tested whether endogenous and exogenous cues produce separate effects on target processing. In Experiment 1, participants discriminated whether an arrow presented left or right of fixation pointed to the left or right. For 1 group, the arrow was preceded by a peripheral noninformative cue. For the other group, the arrow was preceded by a central, symbolic, informative cue. The 2 types of cues modulated the spatial Stroop effect in opposite ways, with endogenous cues producing larger spatial Stroop effects for valid trials and exogenous cues producing smaller spatial Stroop effects for valid trials. In Experiments 2A and 2B, the influence of peripheral noninformative and peripheral informative cues on the spatial Stroop effect was directly compared. The spatial Stroop effect was smaller for valid than for invalid trials for both types of cues. These results point to a distinction between the influence of central and peripheral attentional cues on performance and are not consistent with a unitary view of endogenous and exogenous attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial relevance determines facilitatory and inhibitory effects of auditory covert spatial orienting.

Eight experiments examined the conditions necessary for covert orienting and inhibition of return (IOR) to occur in audition. Spatially uninformative auditory cues facilitated responses to auditory targets at short stimulus onset asynchronies (SOAs) and inhibited them at longer SOAs when the decision to respond was based on the location of the target (Experiments 1, 3, and 4). The same cues did not influence performance when the decision to respond was based on nonspatial criteria (Experiments 2, 5, and 7) unless the cues predicted the location of the target (Experiment 6). In the absence of cues, the location of a previous target influenced performance when the decision to respond was based on spatial, but not nonspatial, criteria (Experiment 8). These findings demonstrate that covert orienting and IOR occur in audition only when spatial relevance is established, presumably inducing use of location-sensitive neurons in generating responses. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Repetition blindness, forward and backward.

In these experiments, 2 letters were presented sequentially to the left and right of fixation, followed by pattern masks. Report was cued by spatial location (Experiments 1a, 1b, 2, 4, and 5) or temporal position (Experiments 3, 4, and 5). In all experiments, 2 identical letters on a trial resulted in reduced accuracy of report (repetition blindness; RB) for both the 1st and 2nd presented letters. This decrement was greater for the 2nd letter if subjects expected temporal cues, but tended to be greater for the Ist letter if they expected spatial cues. Analyses of errors and responses on catch trials indicated no bias against report of repetitions, and the repetition decrement did not interact with output order. The data are inconsistent with both type-refractoriness and memory-retrieval accounts of RB. A modified version of N. G. Kanwisher's (1987) token-individuation theory is proposed to account for the results. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Is Posner's "beam" the same as Treisman's "glue?" On the relation between visual orienting and feature integration theory.

In the present study we investigated whether the visually allocated "beam" studied by Posner and others is the same visual attentional resource that performs the role of feature integration in Treisman's model. Subjects were cued to attend to a certain spatial location by a visual cue, and performance at expected and unexpected stimulus locations was compared. Subjects searched for a target letter (R) with distractor letters that either could give rise to illusory conjunctions (PQ) or could not (PB). Results from three separate experiments showed that orienting attention in response to central cues (endogenous orienting) showed similar effects for both conjunction and feature search. However, when attention was oriented with peripheral visual cues (exogenous orienting), conjunction search showed larger effects of attention than did feature search. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reversal set formation in the visually decorticate rat.

Results of 4 experiments with 32 male black-hooded rats show that Ss given large visual cortex lesions demonstrated a simultaneous task reversal deficit previously reported by R. C. Gonzales et al (1964) to follow more extensive cortical ablation. However, no deficit appeared in an operant discrimination that deemphasized visuospatial cues, and the simultaneous task deficit vanished when translucent eye occluders were applied to eliminate spatial, but not intensity, cue use. Because the lesion Ss showed an impairment only when visuospatial cues were available and relevant to correct reversal performance, they seemed hindered by their incompetent processing of visuospatial information. Results support spatial rather than learning approaches to visual cortex function. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Listening, not watching: Situational familiarity and the ability to detect deception.

In 4 experiments, the authors investigated the influence of situational familiarity with the judgmental context on the process of lie detection. They predicted that high familiarity with a situation leads to a more pronounced use of content cues when making judgments of veracity. Therefore, they expected higher classification accuracy of truths and lies under high familiarity. Under low situational familiarity, they expected that people achieve lower accuracy rates because they use more nonverbal cues for their veracity judgments. In all 4 experiments, participants with high situational familiarity achieved higher accuracy rates in classifying both truthful and deceptive messages than participants with low situational familiarity. Moreover, mediational analyses demonstrated that higher classification accuracy in the high-familiarity condition was associated with more use of verbal content cues and less use of nonverbal cues. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Spatial location is critical for conditioning place preference with visual but not tactile stimuli.

The roles of visual, tactile, and spatial location cues were studied in 6 conditioned place preference (CPP) experiments with ethanol (2 g/kg) in mice (of the DBA/2J strain). Visual cues were effective conditioned stimuli (CSs) when consistently presented in the same spatial location, but not when the same cue was presented in two different locations during training. In contrast, tactile CSs were effective regardless of spatial location during training. Moreover, spatial location controlled CPP expression when visual cues were used but not when tactile cues were used. However, spatial location per se was not an effective CS. These studies suggest that CPP conditioned to tactile cues is mediated by brain systems different from those mediating CPP conditioned to visual-spatial cues. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Behavior of college baseball players in a virtual batting task.

A baseball batting simulation was used to investigate the information used to hit a baseball. Measures of spatial and temporal swing accuracy were used to test whether batters (a) use speed to estimate pitch height, (b) initiate a constant swing duration at a fixed time to contact, (c) are influenced by the history of previous pitches and pitch count, and (d) use rotation direction. Batters were experienced college players. Pitch speed variance led to predictable spatial errors, and spatial accuracy was worse than temporal accuracy. Swing duration was generally variable. The history of the previous 3 pitches and the pitch count had significant effects on accuracy, and performance improved when rotation cues were added. There were significant effects of expertise on hitting strategy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Characteristics of spatial memory in pigeons.

In 4 experiments, adult White King pigeons learned a delayed-alternation (DA) task in a T-maze. Few trials were needed prior to accurate performance. Similarly, after little training, Ss performed accurately with delays of 8–26 min. End-of-delay cues, possibly provided by the experimenter, response-based cues, and intramaze cues were all experimentally examined and rejected as bases for the Ss' performances; pigeons appear to rely on spatial (extramaze) cues. Long-delay performances were undisturbed by changes in delay-interval stimuli (illumination shifts and transportation around the laboratory). Ss acquired DA so quickly because of a potent tendency to avoid recently visited locations (i.e., a preexisting "win-shift" tendency). Characteristics of pigeon spatial memory thus include temporal persistence, resistance to retroactive interference, and win-shift bias. In these respects spatial memory of pigeons parallels spatial memory of rats. (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)