The Jena Voice Learning and Memory Test (JVLMT): A standardized tool for assessing the ability to learn and recognize voices.

The ability to recognize someone's voice spans a broad spectrum with phonagnosia on the low end and super-recognition at the high end. Yet there is no standardized test to measure an individual's ability of learning and recognizing newly learned voices with samples of speech-like phonetic variability. We have developed the Jena Voice Learning and Memory Test (JVLMT), a 22-min test based on item response theory and applicable across languages. The JVLMT consists of three phases in which participants (1) become familiarized with eight speakers, (2) revise the learned voices, and (3) perform a 3AFC recognition task, using pseudo-sentences devoid of semantic content. Acoustic (dis)similarity analyses were used to create items with various levels of difficulty. Test scores are based on 22 items which had been selected and validated based on two online studies with 232 and 454 participants, respectively. Mean accuracy in the JVLMT is 0.51 (SD = .18) with an empirical (marginal) reliability of 0.66. Correlational analyses showed high and moderate convergent validity with the Bangor Voice Matching Test (BVMT) and Glasgow Voice Memory Test (GVMT), respectively, and high discriminant validity with a digit span test. Four participants with potential super recognition abilities and seven participants with potential phonagnosia were identified who performed at least 2 SDs above or below the mean, respectively. The JVLMT is a promising research and diagnostic screening tool to detect both impairments in voice recognition and super-recognition abilities.

Atypical prosopagnosia following right hemispheric stroke: A 23-year follow-up study with M.T.

Most findings on prosopagnosia to date suggest preserved voice recognition in prosopagnosia (except in cases with bilateral lesions). Here we report a follow-up examination on M.T., suffering from acquired prosopagnosia following a large unilateral right-hemispheric lesion in frontal, parietal, and anterior temporal areas excluding core ventral occipitotemporal face areas. Twenty-three years after initial testing we reassessed face and object recognition skills [Henke, K., Schweinberger, S. R., Grigo, A., Klos, T., & Sommer, W. (1998). Specificity of face recognition: Recognition of exemplars of non-face objects in prosopagnosia. Cortex, 34(2), 289-296]; [Schweinberger, S. R., Klos, T., & Sommer, W. (1995). Covert face recognition in prosopagnosia - A dissociable function? Cortex, 31(3), 517-529] and additionally studied voice recognition. Confirming the persistence of deficits, M.T. exhibited substantial impairments in famous face recognition and memory for learned faces, but preserved face matching and object recognition skills. Critically, he showed substantially impaired voice recognition skills. These findings are congruent with the ideas that (i) prosopagnosia after right anterior temporal lesions can persist over long periods > 20 years, and that (ii) such lesions can be associated with both facial and vocal deficits in person recognition.

Parameter-Specific Morphing Reveals Contributions of Timbre to the Perception of Vocal Emotions in Cochlear Implant Users.

OBJECTIVES: Research on cochlear implants (CIs) has focused on speech comprehension, with little research on perception of vocal emotions. We compared emotion perception in CI users and normal-hearing (NH) individuals, using parameter-specific voice morphing. DESIGN: Twenty-five CI users and 25 NH individuals (matched for age and gender) performed fearful-angry discriminations on bisyllabic pseudoword stimuli from morph continua across all acoustic parameters (Full), or across selected parameters (F0, Timbre, or Time information), with other parameters set to a noninformative intermediate level. RESULTS: Unsurprisingly, CI users as a group showed lower performance in vocal emotion perception overall. Importantly, while NH individuals used timbre and fundamental frequency (F0) information to equivalent degrees, CI users were far more efficient in using timbre (compared to F0) information for this task. Thus, under the conditions of this task, CIs were inefficient in conveying emotion based on F0 alone. There was enormous variability between CI users, with low performers responding close to guessing level. Echoing previous research, we found that better vocal emotion perception was associated with better quality of life ratings. CONCLUSIONS: Some CI users can utilize timbre cues remarkably well when perceiving vocal emotions.

Deaf signers outperform hearing non-signers in recognizing happy facial expressions.

The use of signs as a major means for communication affects other functions such as spatial processing. Intriguingly, this is true even for functions which are less obviously linked to language processing. Speakers using signs outperform non-signers in face recognition tasks, potentially as a result of a lifelong focus on the mouth region for speechreading. On this background, we hypothesized that the processing of emotional faces is altered in persons using mostly signs for communication (henceforth named deaf signers). While for the recognition of happiness the mouth region is more crucial, the eye region matters more for recognizing anger. Using morphed faces, we created facial composites in which either the upper or lower half of an emotional face was kept neutral while the other half varied in intensity of the expressed emotion, being either happy or angry. As expected, deaf signers were more accurate at recognizing happy faces than non-signers. The reverse effect was found for angry faces. These differences between groups were most pronounced for facial expressions of low intensities. We conclude that the lifelong focus on the mouth region in deaf signers leads to more sensitive processing of happy faces, especially when expressions are relatively subtle.

The Jena Speaker Set (JESS)-A database of voice stimuli from unfamiliar young and old adult speakers.

Here we describe the Jena Speaker Set (JESS), a free database for unfamiliar adult voice stimuli, comprising voices from 61 young (18-25 years) and 59 old (60-81 years) female and male speakers uttering various sentences, syllables, read text, semi-spontaneous speech, and vowels. Listeners rated two voice samples (short sentences) per speaker for attractiveness, likeability, two measures of distinctiveness ("deviation"-based [DEV] and "voice in the crowd"-based [VITC]), regional accent, and age. Interrater reliability was high, with Cronbach's α between .82 and .99. Young voices were generally rated as more attractive than old voices, but particularly so when male listeners judged female voices. Moreover, young female voices were rated as more likeable than both young male and old female voices. Young voices were judged to be less distinctive than old voices according to the DEV measure, with no differences in the VITC measure. In age ratings, listeners almost perfectly discriminated young from old voices; additionally, young female voices were perceived as being younger than young male voices. Correlations between the rating dimensions above demonstrated (among other things) that DEV-based distinctiveness was strongly negatively correlated with rated attractiveness and likeability. By contrast, VITC-based distinctiveness was uncorrelated with rated attractiveness and likeability in young voices, although a moderate negative correlation was observed for old voices. Overall, the present results demonstrate systematic effects of vocal age and gender on impressions based on the voice and inform as to the selection of suitable voice stimuli for further research into voice perception, learning, and memory.

Electrophysiological correlates of voice learning and recognition.

Listeners can recognize familiar human voices from variable utterances, suggesting the acquisition of speech-invariant voice representations during familiarization. However, the neurocognitive mechanisms mediating learning and recognition of voices from natural speech are currently unknown. Using electrophysiology, we investigated how representations are formed during intentional learning of initially unfamiliar voices that were later recognized among novel voices. To probe the acquisition of speech-invariant voice representations, we compared a "same sentence" condition, in which speakers repeated the study utterances at test, and a "different sentence" condition. Although recognition performance was higher for same compared with different sentences, substantial voice learning also occurred for different sentences, with recognition performance increasing across consecutive study-test-cycles. During study, event-related potentials elicited by voices subsequently remembered elicited a larger sustained parietal positivity (∼250-1400 ms) compared with subsequently forgotten voices. This difference due to memory was unaffected by test sentence condition and may thus reflect the acquisition of speech-invariant voice representations. At test, voices correctly classified as "old" elicited a larger late positive component (300-700 ms) at Pz than voices correctly classified as "new." This event-related potential OLD/NEW effect was limited to the same sentence condition and may thus reflect speech-dependent retrieval of voices from episodic memory. Importantly, a speech-independent effect for learned compared with novel voices was found in beta band oscillations (16-17 Hz) between 290 and 370 ms at central and right temporal sites. Our results are a first step toward elucidating the electrophysiological correlates of voice learning and recognition.

Neural Correlates of Voice Learning with Distinctive and Non-Distinctive Faces.

Recognizing people from their voices may be facilitated by a voice's distinctiveness, in a manner similar to that which has been reported for faces. However, little is known about the neural time-course of voice learning and the role of facial information in voice learning. Based on evidence for audiovisual integration in the recognition of familiar people, we studied the behavioral and electrophysiological correlates of voice learning associated with distinctive or non-distinctive faces. We repeated twelve unfamiliar voices uttering short sentences, together with either distinctive or non-distinctive faces (depicted before and during voice presentation) in six learning-test cycles. During learning, distinctive faces increased early visually-evoked (N170, P200, N250) potentials relative to non-distinctive faces, and face distinctiveness modulated voice-elicited slow EEG activity at the occipito-temporal and fronto-central electrodes. At the test, unimodally-presented voices previously learned with distinctive faces were classified more quickly than were voices learned with non-distinctive faces, and also more quickly than novel voices. Moreover, voices previously learned with faces elicited an N250-like component that was similar in topography to that typically observed for facial stimuli. The preliminary source localization of this voice-induced N250 was compatible with a source in the fusiform gyrus. Taken together, our findings provide support for a theory of early interaction between voice and face processing areas during both learning and voice recognition.

Auditory adaptation in voice perception.

Perceptual aftereffects following adaptation to simple stimulus attributes (e.g., motion, color) have been studied for hundreds of years. A striking recent discovery was that adaptation also elicits contrastive aftereffects in visual perception of complex stimuli and faces [1-6]. Here, we show for the first time that adaptation to nonlinguistic information in voices elicits systematic auditory aftereffects. Prior adaptation to male voices causes a voice to be perceived as more female (and vice versa), and these auditory aftereffects were measurable even minutes after adaptation. By contrast, crossmodal adaptation effects were absent, both when male or female first names and when silently articulating male or female faces were used as adaptors. When sinusoidal tones (with frequencies matched to male and female voice fundamental frequencies) were used as adaptors, no aftereffects on voice perception were observed. This excludes explanations for the voice aftereffect in terms of both pitch adaptation and postperceptual adaptation to gender concepts and suggests that contrastive voice-coding mechanisms may routinely influence voice perception. The role of adaptation in calibrating properties of high-level voice representations indicates that adaptation is not confined to vision but is a ubiquitous mechanism in the perception of nonlinguistic social information from both faces and voices.

Phonetic perception but not perception of speaker gender is impaired in chronic tinnitus.

While tinnitus is known to compromise the perception of speech, it is unclear if the same holds for extralinguistic speaker information. Furthermore, research with simple tone stimuli showed that unilateral tinnitus binds spatial attention, thereby impeding the detection of auditory changes in the non-affected ear. Using dichotic listening tasks, we tested left-ear tinnitus patients and control patients for their ability to ignore speech and speaker information in the task-irrelevant ear. To this end they heard vowel-consonant-vowel (VCV) syllables simultaneously spoken by gender-ambiguous voices in one ear and male or female voices in the contralateral ear. They selectively attended to speech (Exp. 1) or speaker (Exp. 2) information in a designated target ear, by classifying either the consonant (/b/ or /g/) in VCV syllables or voice gender (male or female) while ignoring distractor voices in the other ear. While performance was comparable across groups in the gender task, tinnitus patients responded slower than controls in the consonant task, with no effect of target ear. This suggests that tinnitus hampers phonetic perception in speech, while preserving the processing of extralinguistic speaker information. These findings support the growing evidence for speech perception impairments in tinnitus.

Attractiveness and distinctiveness between speakers' voices in naturalistic speech and their faces are uncorrelated.

Facial attractiveness has been linked to the averageness (or typicality) of a face and, more tentatively, to a speaker's vocal attractiveness, via the 'honest signal' hypothesis, holding that attractiveness signals good genes. In four experiments, we assessed ratings for attractiveness and two common measures of distinctiveness ('distinctiveness-in-the-crowd', DITC and 'deviation-based distinctiveness', DEV) for faces and voices (simple vowels, or more naturalistic sentences) from 64 young adult speakers (32 female). Consistent and substantial negative correlations between attractiveness and DEV generally supported the averageness account of attractiveness, for both voices and faces. By contrast, and indicating that both measures of distinctiveness reflect different constructs, correlations between attractiveness and DITC were numerically positive for faces (though small and non-significant), and significant for voices in sentence stimuli. Between faces and voices, distinctiveness ratings were uncorrelated. Remarkably, and at variance with the honest signal hypothesis, vocal and facial attractiveness were also uncorrelated in all analyses involving naturalistic, i.e. sentence-based, speech. This result pattern was confirmed using a new set of stimuli and raters (experiment 5). Overall, while our findings strongly support an averageness account of attractiveness for both domains, they provide no evidence for an honest signal account of facial and vocal attractiveness in complex naturalistic speech.

The Role of Stimulus Type and Social Signal for Voice Perception in Cochlear Implant Users: Response to the Letter by Meister et al.

Purpose In their letter, Meister et al. (2020) appropriately point to a potential influence of stimulus type, arguing cochlear implant (CI) users may have the ability to use timbre cues only for complex stimuli such as sentences but not for brief stimuli such as vowel-consonant-vowel or single words. While we cannot exclude this possibility on the basis of Skuk et al. (2020) alone, we hold that there is a strong need to consider type of social signal (e.g., gender, age, emotion, speaker identity) to assess the profile of preserved and impaired aspects of voice processing in CI users. We discuss directions for further research to systematically consider interactive effects of stimulus type and social signal. In our view, this is crucial to understand and enhance nonverbal vocal perception skills that are relevant to successful communication with a CI.

In the ear of the beholder: neural correlates of adaptation to voice gender.

While high-level adaptation to faces has been extensively investigated, research on behavioural and neural correlates of auditory adaptation to paralinguistic social information in voices has been largely neglected. Here we replicate novel findings that adaptation to voice gender causes systematic contrastive aftereffects such that repeated exposure to female voice adaptors causes a subsequent test voice to be perceived as more male (and vice versa), even minutes after adaptation [S.R. Schweinberger et al., (2008), Current Biology, 18, 684-688). In addition, we recorded event-related potentials to test-voices morphed along a gender continuum. An attenuation in frontocentral N1-P2 amplitudes was seen when a test voice was preceded by gender-congruent voice adaptors. Additionally, similar amplitude attenuations were seen in a late parietal positive component (P3, 300-700 ms). These findings suggest that contrastive coding of voice gender takes place within the first few hundred milliseconds from voice onset, and is implemented by neurons in auditory areas that are specialised for detecting male and female voice quality.

Voices to remember: Comparing neural signatures of intentional and non-intentional voice learning and recognition.

Recent electrophysiological evidence suggests a rapid acquisition of novel speaker representations during intentional voice learning. We investigated effects of learning intention on voice recognition, using a variant of the directed forgetting paradigm. In an old/new recognition task following voice learning, we compared performance and event-related brain potentials (ERPs) for studied voices, half of which had been prompted to be remembered (TBR) or forgotten (TBF). Furthermore, to assess incidental encoding of episodic information, participants indicated for each recognized test voice the ear of presentation during study. During study, TBR voices elicited more positive ERPs than TBF voices (from ∼250 ms), possibly reflecting deeper voice encoding. In parallel, subsequent recognition performance was higher for TBR than for TBF voices. Importantly, above-chance recognition for both learning conditions nevertheless suggested a degree of non-intentional voice learning. In a surprise episodic memory test for voice location, above-chance performance was observed for TBR voices only, suggesting that episodic memory for ear of presentation depended on intentional voice encoding. At test, a left posterior ERP OLD/NEW effect for both TBR and TBF voices (from ∼500 ms) reflected recognition of studied voices under both encoding conditions. By contrast, a right frontal ERP OLD/NEW effect for TBF voices only (from ∼800 ms) possibly reflected additional elaborative retrieval processes. Overall, we show that ERPs are sensitive 1) to strategic voice encoding during study (from ∼250 ms), and 2) to voice recognition at test (from ∼500 ms), with the specific pattern of ERP OLD/NEW effects partly depending on previous encoding intention.

Investigating the common set of acoustic parameters in sexual orientation groups: A voice averaging approach.

While the perception of sexual orientation in voices often relies on stereotypes, it is unclear whether speech stereotypes and accurate perceptions of sexual orientation are each based on acoustic cues common to speakers of a given group. We ask if the stereotypical belief, that members of the same sexual orientation group share similar acoustic patterns, is accurate to some degree. To address this issue, we are the first to use a novel voice morphing technique to create voice averages from voices that represent extremes of a given sexual orientation group either in terms of actual or perceived sexual orientation. Importantly, averaging preserves only those acoustic cues shared by the original speakers. 144 German listeners judged the sexual orientation of twelve natural-sounding sentence stimuli, each representing an average of five original utterances. Half of the averages were based on targets' self-ratings of sexual orientation: On a 7-point Kinsey-like scale, we selected targets who were most typical for a certain sexual orientation group according to their self-identifications. The other half were based on extreme ratings by others (i.e., on speech-related sexual-orientation stereotypes). Listeners judged sexual orientation from the voice averages with above-chance accuracy suggesting 1) that the perception of actual and stereotypical sexual orientation, respectively, are based on acoustic cues shared by speakers of the same group, and 2) that the stereotypical belief that members of the same sexual orientation group share similar acoustic patterns is accurate to some degree. Mean fundamental frequency and other common acoustic parameters showed systematic variation depending on speaker gender and sexual orientation. Effects of sexual orientation were more pronounced for stereotypical voice averages than for those based on speakers' self-ratings, suggesting that sexual-orientation stereotypes exaggerate even those differences present in the most salient groups of speakers. Implications of our findings for stereotyping and discrimination are discussed.

Electrophysiological correlates of voice memory for young and old speakers in young and old listeners.

Faces of one's own-age group are easier to recognize than other-age faces. Using behavioral measures and EEG, we studied whether an own-age bias (OAB) also exists in voice memory. Young (19 - 26 years) and old (60-75 years) participants studied young (18-25 years) and old (60-77 years) unfamiliar voices from short sentences. Subsequently, they classified studied and novel voices as "old" (i.e. studied) or "new", from the same sentences. Recognition performance was higher in young compared to old participants, and for old compared to young voices, with no OAB. At the same time, we found evidence for higher distinctiveness of old compared to young voices, both in terms of acoustic measures and subjective ratings (independent of rater age). Analyses of event-related brain potentials (ERPs) indicated more negative-going deflections (400-1000ms) for old compared to young voices in young participants. In old participants, we observed a reversed OLD/NEW memory effect, with overall more positive amplitudes for novel compared to studied old (but not young) voices (400-1000ms). Time-frequency analyses revealed less beta power (16-26Hz) for young compared to old voices at left anterior sites, and also reduced beta power for correctly recognized studied (compared to novel) voices at left posterior sites (300-900ms). These findings could suggest an engagement of cortical areas during stimulus-specific recollection from about 300ms, in a task that emphasized the analysis of individual acoustic features.

It doesn't matter what you say: FMRI correlates of voice learning and recognition independent of speech content.

Listeners can recognize newly learned voices from previously unheard utterances, suggesting the acquisition of high-level speech-invariant voice representations during learning. Using functional magnetic resonance imaging (fMRI) we investigated the anatomical basis underlying the acquisition of voice representations for unfamiliar speakers independent of speech, and their subsequent recognition among novel voices. Specifically, listeners studied voices of unfamiliar speakers uttering short sentences and subsequently classified studied and novel voices as "old" or "new" in a recognition test. To investigate "pure" voice learning, i.e., independent of sentence meaning, we presented German sentence stimuli to non-German speaking listeners. To disentangle stimulus-invariant and stimulus-dependent learning, during the test phase we contrasted a "same sentence" condition in which listeners heard speakers repeating the sentences from the preceding study phase, with a "different sentence" condition. Voice recognition performance was above chance in both conditions although, as expected, performance was higher for same than for different sentences. During study phases activity in the left inferior frontal gyrus (IFG) was related to subsequent voice recognition performance and same versus different sentence condition, suggesting an involvement of the left IFG in the interactive processing of speaker and speech information during learning. Importantly, at test reduced activation for voices correctly classified as "old" compared to "new" emerged in a network of brain areas including temporal voice areas (TVAs) of the right posterior superior temporal gyrus (pSTG), as well as the right inferior/middle frontal gyrus (IFG/MFG), the right medial frontal gyrus, and the left caudate. This effect of voice novelty did not interact with sentence condition, suggesting a role of temporal voice-selective areas and extra-temporal areas in the explicit recognition of learned voice identity, independent of speech content.

To hear or not to hear: Voice processing under visual load.

Adaptation to female voices causes subsequent voices to be perceived as more male, and vice versa. This contrastive aftereffect disappears under spatial inattention to adaptors, suggesting that voices are not encoded automatically. According to Lavie, Hirst, de Fockert, and Viding (2004), the processing of task-irrelevant stimuli during selective attention depends on perceptual resources and working memory. Possibly due to their social significance, faces may be an exceptional domain: That is, task-irrelevant faces can escape perceptual load effects. Here we tested voice processing, to study whether voice gender aftereffects (VGAEs) depend on low or high perceptual (Exp. 1) or working memory (Exp. 2) load in a relevant visual task. Participants adapted to irrelevant voices while either searching digit displays for a target (Exp. 1) or recognizing studied digits (Exp. 2). We found that the VGAE was unaffected by perceptual load, indicating that task-irrelevant voices, like faces, can also escape perceptual-load effects. Intriguingly, the VGAE was increased under high memory load. Therefore, visual working memory load, but not general perceptual load, determines the processing of task-irrelevant voices.

Benefits for Voice Learning Caused by Concurrent Faces Develop over Time.

Recognition of personally familiar voices benefits from the concurrent presentation of the corresponding speakers' faces. This effect of audiovisual integration is most pronounced for voices combined with dynamic articulating faces. However, it is unclear if learning unfamiliar voices also benefits from audiovisual face-voice integration or, alternatively, is hampered by attentional capture of faces, i.e., "face-overshadowing". In six study-test cycles we compared the recognition of newly-learned voices following unimodal voice learning vs. bimodal face-voice learning with either static (Exp. 1) or dynamic articulating faces (Exp. 2). Voice recognition accuracies significantly increased for bimodal learning across study-test cycles while remaining stable for unimodal learning, as reflected in numerical costs of bimodal relative to unimodal voice learning in the first two study-test cycles and benefits in the last two cycles. This was independent of whether faces were static images (Exp. 1) or dynamic videos (Exp. 2). In both experiments, slower reaction times to voices previously studied with faces compared to voices only may result from visual search for faces during memory retrieval. A general decrease of reaction times across study-test cycles suggests facilitated recognition with more speaker repetitions. Overall, our data suggest two simultaneous and opposing mechanisms during bimodal face-voice learning: while attentional capture of faces may initially impede voice learning, audiovisual integration may facilitate it thereafter.

Speaker perception.

While humans use their voice mainly for communicating information about the world, paralinguistic cues in the voice signal convey rich dynamic information about a speaker's arousal and emotional state, and extralinguistic cues reflect more stable speaker characteristics including identity, biological sex and social gender, socioeconomic or regional background, and age. Here we review the anatomical and physiological bases for individual differences in the human voice, before discussing how recent methodological progress in voice morphing and voice synthesis has promoted research on current theoretical issues, such as how voices are mentally represented in the human brain. Special attention is dedicated to the distinction between the recognition of familiar and unfamiliar speakers, in everyday situations or in the forensic context, and on the processes and representational changes that accompany the learning of new voices. We describe how specific impairments and individual differences in voice perception could relate to specific brain correlates. Finally, we consider that voices are produced by speakers who are often visible during communication, and review recent evidence that shows how speaker perception involves dynamic face-voice integration. The representation of para- and extralinguistic vocal information plays a major role in person perception and social communication, could be neuronally encoded in a prototype-referenced manner, and is subject to flexible adaptive recalibration as a result of specific perceptual experience. WIREs Cogn Sci 2014, 5:15-25. doi: 10.1002/wcs.1261 CONFLICT OF INTEREST: The authors have declared no conflicts of interest for this article. For further resources related to this article, please visit the WIREs website.

Spatial inattention abolishes voice adaptation.

Adaptation to male voices causes a subsequent voice to be perceived as more female, and vice versa. Similar contrastive aftereffects have been reported for phonetic perception, and in vision for face perception. However, while aftereffects in the perception of phonetic features of speech have been reported to persist even when adaptors were processed inattentively, face aftereffects were previously reported to be abolished by inattention to adaptors. Here we demonstrate that auditory aftereffects of adaptation to voice gender are eliminated when the male and female adaptor voices are spatially unattended. Participants simultaneously heard gender-specific male or female adaptor voices in one ear and gender-neutral (androgynous) adaptor voices in the contralateral ear. They selectively attended to the adaptor voices in a designated ear, by either classifying voice gender (Exp. 1) or spoken syllable (Exp. 2). Voice aftereffects were found only if the gender-specific voices were spatially attended, suggesting capacity limits in the processing of voice gender for the unattended ear. Remarkably, gender-specific adaptors in the attended ear elicited comparable aftereffects in test voices, regardless of prior attention to voice gender or phonetic content. Thus, within the attended ear, voice gender was processed even when it was irrelevant for the task at hand, suggesting automatic processing of gender along with linguistic information. Overall, voice gender adaptation requires spatial, but not dimensional, selective attention.