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Physiological and Behavioral Parameters of Infants' Categorization: Changes in Heart Rate and Duration of Examining across Trials

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Title: Physiological and Behavioral Parameters of Infants' Categorization: Changes in Heart Rate and Duration of Examining across Trials
Language: English
Authors: Elsner, Birgit, Pauen, Sabina, Jeschonek, Susanna
Source: Developmental Science. Nov 2006 9(6):551-556.
Availability: Wiley-Blackwell. 350 Main Street, Malden, MA 02148. Tel: 800-835-6770; Tel: 781-388-8598; Fax: 781-388-8232; e-mail: cs-journals@wiley.com; Web site: http://www.wiley.com/WileyCDA/
Peer Reviewed: Y
Physical Description: PDF
Page Count: 6
Publication Date: 2006
Document Type: Journal Articles
Reports - Research
Descriptors: Metabolism, Infants, Classification, Physiology, Task Analysis, Attention, Familiarity, Measures (Individuals), Cognitive Processes, Behavior Patterns
DOI: 10.1111/j.1467-7687.2006.00532.x
ISSN: 1363-755X
Abstract: This report investigates the relations between duration of examining and heart rate (HR) across several trials of an object-examination task. A total of N= 20 11-month-olds were familiarized with a sequence of 10 different exemplars from the same global category (animals or furniture) before they received an exemplar from the contrasting category at test. Consistent with previous findings, HR was lower during states of focused attention (i.e. examining) than during states of casual attention (i.e. looking) or non-looking. Over the familiarization trials, examining stayed about the same, while mean HR increased. At test, examining increased and mean HR decreased, indicating that infants focused their attention on the out-of-category object. Psychophysiological and behavioral measures of attention were systematically related over trials, suggesting that heart rate provides a suitable objective measure to study infants' categorization performance in object-examination tasks.
Abstractor: As Provided
Number of References: 20
Entry Date: 2009
Accession Number: EJ850138
Database: ERIC
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  Value: <anid>AN0022816752;5g501nov.06;2019May28.13:05;v2.2.500</anid> <title id="AN0022816752-1">Physiological and behavioral parameters of infants’ categorization: changes in heart rate and duration of examining across trials. </title> <p>This report investigates the relations between duration of examining and heart rate (HR) across several trials of an object‐examination task. A total of N= 20 11‐month‐olds were familiarized with a sequence of 10 different exemplars from the same global category (animals or furniture) before they received an exemplar from the contrasting category at test. Consistent with previous findings, HR was lower during states of focused attention (i.e. examining) than during states of casual attention (i.e. looking) or non‐looking. Over the familiarization trials, examining stayed about the same, while mean HR increased. At test, examining increased and mean HR decreased, indicating that infants focused their attention on the out‐of‐category object. Psychophysiological and behavioral measures of attention were systematically related over trials, suggesting that heart rate provides a suitable objective measure to study infants' categorization performance in object‐examination tasks.</p> <p>Studies on categorization investigate infants' ability to classify objects in the world around them. In a typical object‐categorization paradigm, infants are first familiarized with different‐looking exemplars from the same category. At test, infants get an exemplar of a contrasting category, presented either following the last familiarization item or in combination with it ([<reflink idref="bib6" id="ref1">6</reflink>]; [<reflink idref="bib13" id="ref2">13</reflink>]; [<reflink idref="bib14" id="ref3">14</reflink>]). If infants pay more attention to the out‐of‐category item than to the last same‐category item, they are assumed to discriminate both categories. To assess infants' attention, most studies on object categorization use behavioral data.</p> <p>In visual familiarization‐novelty‐preference tasks (VFNPT), pictures of objects are presented, and looking time serves as the dependent variable, i.e. the amount of time that the infant gazes at each picture during a given trial ([<reflink idref="bib14" id="ref4">14</reflink>]). In object‐examination tasks (OET), 3D toy models of real‐world objects are presented ([<reflink idref="bib7" id="ref5">7</reflink>], [<reflink idref="bib8" id="ref6">8</reflink>]; [<reflink idref="bib13" id="ref7">13</reflink>]). [<reflink idref="bib17" id="ref8">17</reflink>], [<reflink idref="bib18" id="ref9">18</reflink>]) analyzed infants' behavior during manual object exploration and found different behavioral patterns that indicate different 'attentive states'. Sometimes, infants looked at the object and manipulated it with an intent facial expression, while at other times, they mouthed the object, banged it, or looked at it in a more uninterested fashion. Ruff called the former behavior <emph>examining</emph>, and she revealed that the duration of examining declines over the course of object exploration, as the familiarity with the object increases. Examining thus reflects focused attention, that is, an exploratory and information‐gathering activity, accompanied by an active intake of information about the object (see [<reflink idref="bib10" id="ref10">10</reflink>]). The duration of mouthing, banging, and looking does not decrease during object exploration, so these activities reflect casual attention, which is non‐exploratory.</p> <p>Unlike VFNPT, OET allows us to determine different degrees of attention (i.e. examining, looking) based on behavioral data in object‐categorization studies (e.g. [<reflink idref="bib7" id="ref11">7</reflink>], [<reflink idref="bib8" id="ref12">8</reflink>]; [<reflink idref="bib9" id="ref13">9</reflink>]). Examining is typically scored off‐line from video by well‐trained coders. During each trial, phases of examining are cumulated to provide a sum score. Despite the fact that inter‐coder agreement is generally quite high (>.85), this type of measurement is often regarded with some skepticism because it can be influenced by knowledge of the hypotheses, experience of the coders, or other factors.</p> <p>Another option to assess attention in stimulus‐exploration tasks comprises the use of objective psychophysiological measures like heart rate (HR). Since the times of [<reflink idref="bib20" id="ref14">20</reflink>]), states of focused attention are assumed to be correlated with low HR measures. Heart rate deceleration is part of the orienting response, and thus indicates a shift of attention towards a novel or unexpected stimulus. Based on this insight, infant researchers explored the relation between behavioral and physiological measures of attention. One of the first studies was provided by [<reflink idref="bib15" id="ref15">15</reflink>]), who found that a single episode of visual stimulus fixation was accompanied by systematic changes in heart rate: HR decelerated at the onset of the stimulus, stayed on a low level for a while, and then returned to pre‐stimulus level. Because HR decelerated in a phase when the infant gathered information about the stimulus, Richards and Casey took systematic HR changes as psychophysiological markers of different attentive states. Likewise, Colombo and collaborators ([<reflink idref="bib2" id="ref16">2</reflink>]; [<reflink idref="bib3" id="ref17">3</reflink>]) combined HR with looking time measures in a VFNPT and found that longer durations of looking within a single trial were associated with more time spent in phases of HR deceleration.</p> <p>Recently, [<reflink idref="bib5" id="ref18">5</reflink>]) investigated systematic variations of HR within a single trial of manual object exploration. They found that 6‐ to 12‐month‐old infants took longer to orient to a peripherally presented distractor during phases of examining than during behaviorally defined casual attention, and longer during phases of lower HR than during higher HR. This suggests that low HR reflects states of focused attention in object‐manipulation tasks. Supporting this idea, [<reflink idref="bib4" id="ref19">4</reflink>]) reported that HR generally decelerated during phases of examining in a single trial of object exploration. It should be noted, however, that HR deceleration and behaviorally defined states of examining do not show perfect agreement. [<reflink idref="bib5" id="ref20">5</reflink>]) observed that examining (i.e. focused attention) was sometimes accompanied by HR acceleration rather than deceleration, and [<reflink idref="bib4" id="ref21">4</reflink>]) found only a loose association between behavioral and physiological measures of attention when examining and looking were alternately occurring within a single look.</p> <p>As this short review reveals, <emph>object examination</emph> plays a key role not only in categorization studies, but also in studies investigating the relation between behavioral and physiological measures of attention. The purpose of the present report was to combine these two lines of research. We reasoned that categorization studies could benefit from using physiological parameters together with behaviorally defined measures of attention, because the former are acquired in a more objective way and could be used to validate the latter. Yet, important differences between both lines of research make the development of an economic method to combine these measures a challenging enterprise: Research on categorization focuses on changes in attention <emph>across different trials.</emph> During each trial, the infant may spent multiple episodes in a state of focused attention. The raw data are sum‐scores of the durations of these episodes per trial, and these sum‐scores are then compared across trials. In contrast, research on attention investigates relations between behaviorally defined and physiologically defined attentive states <emph>within a given trial</emph>. This is typically done by assessing changes in HR after stimulus onset in relation to the prestimulus interval, and by comparing these difference scores to behavioral measures.</p> <p>To bridge the methodological gap between these approaches, we followed this line of thought: If episodes of focused attention go along with a decrease in heart rate (as has been shown by attention researchers), and if infants spend more time of a given trial in focused attention when they are interested in the stimulus (as has been shown by categorization researchers), then mean HR should be low for trials with high examining sum‐scores. Based on these arguments, three hypotheses can be derived on the relation of HR and duration of examining across trials in an OET: (<reflink idref="bib1" id="ref22">1</reflink>) A <emph>decrease</emph> in examining duration over the familiarization trials (i.e. a familiarization effect) should go along with an <emph>increase</emph> in mean HR. (<reflink idref="bib2" id="ref23">2</reflink>) An <emph>increase</emph> in examining duration from the last familiarization trial to the out‐of‐category test trial (i.e. a categorization effect) should go along with a <emph>decrease</emph> in mean HR. (<reflink idref="bib3" id="ref24">3</reflink>) Mean HR should vary for different behaviorally defined states of attention, with phases of examining showing lower heart rates than phases of looking.</p> <hd id="AN0022816752-2">Method</hd> <p>To test the three hypotheses, we presented 11‐month‐olds with toy exemplars of the categories 'animals' and 'furniture' in an object examination task. The use of this age group and this categorical contrast allowed us to predict changes in duration of examining based on previous findings (e.g. [<reflink idref="bib8" id="ref25">8</reflink>]; [<reflink idref="bib12" id="ref26">12</reflink>]). [<reflink idref="bib11" id="ref27">11</reflink>]) tested 11‐month‐olds with the same animal–furniture contrast, presenting either nine or 10 different exemplars of the same category for familiarization, followed by one exemplar of the contrasting category at test. Examining duration decreased from the first to the second phase of the familiarization period, and increased again when the out‐of‐category item was presented. The design of the present study parallels this work, with the difference that HR data were collected in addition to behavioral data.</p> <hd id="AN0022816752-3">Participants</hd> <p>Twenty healthy, full‐term infants participated in the study (<emph>M</emph> age: 11 months, 12 days; range: 11;00 to 11;28). Ten infants were male, ten female. Infants' names came from the residents' registration office, and their families were contacted via letters and phone calls. Eight additional infants were tested, but their data had to be excluded due to fussing (<emph>n</emph>= 3), movement artifacts in the electrocardiogram (<emph>n</emph>= 3), or experimental errors (<emph>n</emph>= 2).</p> <hd id="AN0022816752-4">Materials</hd> <p>Stimuli were realistic toy exemplars of the categories animals and furniture (see Figure 1), about 10 cm in size. The animals were a turtle, a crocodile, a hippopotamus, a zebra, a giraffe, an eagle, a ladybird, a dog, a rabbit, and a fish. The furniture items were an armchair, a chair, a stool, a couch, a wardrobe, a bed, a chest of drawers, a table, a cupboard, and a crib. All objects varied substantially in color and form.</p> <p>Graph: 1 Stimulus material used in the object‐examination task: realistic toy models of animals (left) and furniture items (right).</p> <hd id="AN0022816752-5">Apparatus, design and procedure</hd> <p>A research assistant placed the electrocardiogram (ECG) electrodes on the infant's chest, and then the infant was seated in a highchair with an attached tray. The caregiver sat to the infant's right, and the experimenter sat to the left. The assistant surveying the ECG recording was hidden from the infant's view behind a curtain. After a short warm‐up period, the experimenter placed the first object in front of the infant. For a period of 20 seconds, the infant could freely explore the toy. If the object fell to the floor, it was quickly picked up and placed back on to the table. After 20 s, the experimenter took the object from the infant and presented the next one.</p> <p>Each infant received 10 different exemplars from one category, and then got one exemplar from the other category at test. A similar procedure was used by [<reflink idref="bib16" id="ref28">16</reflink>]) and by [<reflink idref="bib11" id="ref29">11</reflink>], [<reflink idref="bib12" id="ref30">12</reflink>]). The out‐of‐category item was always presented last for theoretical reasons: When infants receive a within‐category item after the out‐of‐category item, they perceive two changes in category rather than only one. So far, no theoretical model predicts how this should affect infants' responses. As has been shown by [<reflink idref="bib11" id="ref31">11</reflink>]), an increase of attention in response to the out‐of‐category item occurs independently of whether this item is presented on trial 10 or 11.</p> <p>Half of the infants (gender balanced) were familiarized with animals, the other half with furniture items. The presentation order of the familiarization objects varied systematically across infants, and each infant got a different out‐of‐category object at test. The whole session lasted for about 7 minutes and was videotaped for later coding.</p> <hd id="AN0022816752-6">Measurement of HR</hd> <p>HR was measured with three Ag‐AgCl electrodes placed on the infant's chest. The ECG was sampled with 100 Hz and digitized by a data acquisition interface (BioPac Inc., Santa Barbara, CA). The computer software identified the R‐wave of the ECG and computed the HR in beats per minute (bpm) on‐line. The laboratory assistant coded each 20‐s period of stimulus presentation by pressing a button connected to the ECG‐computer. The button signal was recorded parallel to the ECG data to allow the synchronization of behavioral codes and HR for analyses, and the computation of mean HR (bpm) for each trial.</p> <hd id="AN0022816752-7">Measurement of examining (behavioral analysis)</hd> <p>In a first step of data analysis, infants' behavior was scored off‐line by two independent observers, one of whom had not been involved in the process of data collection. <emph>Examining</emph> was coded when the infant was concentrating on and inspecting the object (see [<reflink idref="bib9" id="ref32">9</reflink>]; [<reflink idref="bib17" id="ref33">17</reflink>]). Mean inter‐rater reliability for examining was <emph>r</emph>=.92. For each trial, the mean of the scores of both observers provided the raw data for further analyses.</p> <hd id="AN0022816752-8">Combination of physiological and behavioral data</hd> <p>The behavioral data were scored with INTERACT (Mangold Software, Munich, Germany). This allowed the synchronization of the behavioral codes and the HR data: Each 20‐s trial was divided into 100 200‐ms intervals. A mean HR value in bpm was computed for each interval. In addition, we scored infants' behavior in three categories: (<reflink idref="bib1" id="ref34">1</reflink>) <emph>examining</emph>, defined as focused attention towards the object, (<reflink idref="bib2" id="ref35">2</reflink>) <emph>looking</emph>, defined as non‐focused visual attention towards the object, and (<reflink idref="bib3" id="ref36">3</reflink>) <emph>other</emph> behavior (i.e. neither examining nor looking). If an infant spent more than 50% of a given 200‐ms interval with a given activity, the corresponding behavioral category was scored '1', and otherwise, it was scored '0'. Thus, only one of the three categories scored '1' for any given 200‐ms interval. Mean inter‐coder reliability for all categories was <emph>r</emph>=.92. To prevent coding biases, HR data were added to the data files only after the behavioral measures had been scored.</p> <p>We used the mean HR and sum‐scores of examining duration per 20‐s trial to analyze changes in infants' responses across the familiarization and test trials, and the interval‐coding (200 ms) to test whether different states of attention are systematically related to differences in mean HR. In the latter case, data were accumulated across all trials, and mean HR was compared between the three behavior categories for all phases spent in this behaviorally defined state of attention.</p> <hd id="AN0022816752-9">Results</hd> <p></p> <hd id="AN0022816752-10">Duration of examining</hd> <p>The mean durations of examining for the 10 familiarization trials and the test trial are shown in Figure 2. To test for a familiarization effect, the mean examining duration was computed for the first five familiarization trials (Phase A) and for the last five familiarization trials (Phase B). A <emph>t‐</emph>test yielded no significant difference between Phase A (<emph>M</emph>= 5.3 s, SD = 1.8) and Phase B (<emph>M</emph>= 5.2 s, SD = 2.3), <emph>t</emph>(<reflink idref="bib19" id="ref37">19</reflink>) =.17, <emph>p</emph>=.44. However, as can be seen in Figure 2, duration of examining increased significantly from the last familiarization object (<emph>M</emph>= 4.7 s, SD = 4.3) to the out‐of‐category test object (<emph>M</emph>= 8.0 s, SD = 3.8), <emph>t</emph>(<reflink idref="bib19" id="ref38">19</reflink>) =−3.88, <emph>p <</emph>.001.</p> <p>Graph: 2 Mean duration of examining (in seconds) and mean heart rate (in beats per minute, bpm) in the 10 familiarization trials (F1–F10) and the test trial (Test).</p> <hd id="AN0022816752-11">Heart rate</hd> <p>The mean HR for each trial is shown in Figure 2. The mean HR during the first five familiarization trials (Phase A) was computed and compared to the mean HR during the last five familiarization trials (Phase B). A <emph>t</emph>‐test revealed a significant increase in HR from Phase A (<emph>M</emph>= 129 bpm, SD = 11.5) to Phase B (<emph>M</emph>= 132 bpm, SD = 10.4), <emph>t</emph>(<reflink idref="bib19" id="ref39">19</reflink>) =−4.11, <emph>p</emph> <.001. Furthermore, HR decreased significantly from the last familiarization trial (<emph>M</emph>= 133 bpm, SD = 10.0) to the test trial (<emph>M</emph>= 131 bpm, SD = 10.4), <emph>t</emph>(<reflink idref="bib19" id="ref40">19</reflink>) = 2.09, <emph>p</emph> <.05.</p> <hd id="AN0022816752-12">Relations between behaviorally defined attentive states and heart rate</hd> <p>The mean HR scores for the three behavior categories are shown in Figure 3. The HR scores were entered into a one‐way analysis of variance (ANOVA) with behavior category (<emph>examining</emph>, <emph>looking</emph>, <emph>other</emph>) as within‐subject factor. This analysis revealed a significant main effect, <emph>F</emph>(<reflink idref="bib2" id="ref41">2</reflink>, 38) = 14.75, <emph>p</emph> <.001, indicating differences in HR between the behaviorally defined attentive states.</p> <p>Graph: 3 Mean heart rate in beats per minute (bpm) during the behaviorally defined attentive states, including data from all trials, i.e. 10 familiarization trials and 1 test trial.</p> <p>Separate <emph>t</emph>‐tests showed that HR differed significantly between all behavior categories (<emph>examining</emph> vs. <emph>looking</emph>: <emph>t</emph>(<reflink idref="bib19" id="ref42">19</reflink>) =−2.52, <emph>p</emph>=.01; <emph>examining</emph> vs. <emph>other</emph>: <emph>t</emph>(<reflink idref="bib19" id="ref43">19</reflink>) =−4.48, <emph>p</emph> <.001; <emph>looking</emph> vs. <emph>other</emph>: <emph>t</emph>(<reflink idref="bib19" id="ref44">19</reflink>) =−3.86, <emph>p</emph> <.001). Consistent with our expectations, the mean HR was lowest during <emph>examining</emph> and highest during <emph>other behavior</emph>, while the HR for <emph>looking</emph> lay somewhere in‐between.</p> <hd id="AN0022816752-13">Discussion</hd> <p>The present study explored whether physiological parameters (i.e. mean HR) and behavioral measures of infant attention (i.e. duration of examining) are systematically related in an object‐examination task. Contrary to previous research, we did not analyze changes in attention and HR during one single trial, but explored mean differences across several trials. Based upon the idea that infants spend more time in states of focused attention at the beginning than at the end of the familiarization phase ([<reflink idref="bib17" id="ref45">17</reflink>], [<reflink idref="bib18" id="ref46">18</reflink>]), we expected to find a decrease in duration of examining and an increase in mean HR from the first to the second half of the familiarization phase. This hypothesis was confirmed by the HR data, but not by the behavioral data. Additionally, we expected an increase in duration of examining and a decrease in mean HR from the last familiarization trial to the test trial. Both the HR and the behavioral data displayed this pattern. Infants showed a clear categorization effect at the end of the session, replicating the finding that 11‐month‐olds are able to differentiate the categories of animals and furniture items ([<reflink idref="bib8" id="ref47">8</reflink>]; [<reflink idref="bib11" id="ref48">11</reflink>], [<reflink idref="bib13" id="ref49">13</reflink>]). But more importantly, these results indicate that we succeeded in combining behaviorally defined and physiological measures of attention across several trials in an OET. Mean HR and duration of examining varied systematically and in the expected direction for the categorization effect, indicating that objective physiological measures can be recorded in an economic way to validate the more subjective behaviorally defined measures of attention.</p> <p>In the present study, behaviorally defined phases of focused attention (i.e. examining) were accompanied by significantly lower mean HR scores than phases of casual attention (i.e. looking), and mean HR was highest in periods without visual attention (i.e. other). This corresponds to findings by Lansink and collaborators for single‐trial analyses ([<reflink idref="bib5" id="ref50">5</reflink>]; [<reflink idref="bib4" id="ref51">4</reflink>]) and supports the assumption that attention is a phenomenon involving more than one psychological process ([<reflink idref="bib17" id="ref52">17</reflink>], [<reflink idref="bib18" id="ref53">18</reflink>]). Previous work suggests that HR starts decreasing only after the onset of a behaviorally defined state of focused attention ([<reflink idref="bib4" id="ref54">4</reflink>]; [<reflink idref="bib15" id="ref55">15</reflink>]). The present method of combining behavioral and physiological measures did not take this time‐lag into account. Hence, the mean HR score obtained for phases of examining may be slightly higher than the true value, thus washing out differences in HR between states of examining and looking. Despite this potential problem, we found mean HR to be significantly lower during examining than during looking, thus suggesting that the underlying relation between attentive states and HR is a rather strong one.</p> <p>It remains an open question why HR and examining data did not co‐vary in the expected way for the familiarization trials. It should be noted that categorization studies often fail to find a familiarization effect in looking times or duration of examining ([<reflink idref="bib1" id="ref56">1</reflink>]; [<reflink idref="bib8" id="ref57">8</reflink>]). Yet, this does not imply that infants do not respond to similarities among the familiarization stimuli. Rather, the lack of a familiarization effect may be attributed to the fact that each item of the category provides new information to be processed, thus keeping infants' attention at a high level, although the commonalities of the objects are still encoded ([<reflink idref="bib9" id="ref58">9</reflink>]).</p> <p>One way to explain the discrepancy of the behavioral and the HR data in the familiarization trials would be that the increase in mean HR does not reflect a habituation to the presented category, but rather a general adaptation to the experimental situation. Colombo and others ([<reflink idref="bib3" id="ref59">3</reflink>]; [<reflink idref="bib19" id="ref60">19</reflink>]) reported that in a visual stimulus‐exploration task, infants' HR during the inter‐trial intervals (i.e. when no stimulus was present) increased across trials, probably reflecting general adaptation processes. However, the results from the test phase rule out this alternative explanation: In our setting, the test trial was the very last trial, so the fact that mean HR <emph>decreased</emph> from the last familiarization to the test trial (i.e. from trial 10 to trial 11) confirms that HR was influenced by changes in attention. Attention‐tied HR changes may be superimposed by a general adaptation to the experimental setting, but still, HR varied systematically with behaviorally defined attentive states across trials in the present study.</p> <p>As pointed out by Lansink and others ([<reflink idref="bib5" id="ref61">5</reflink>]; [<reflink idref="bib4" id="ref62">4</reflink>]), physiological and behavioral measures of attention do not match perfectly, even when analyzing HR changes within a given trial rather than mean HR scores across trials. [<reflink idref="bib5" id="ref63">5</reflink>], p. 619) speculated that 'the changes in heart rate and the behavioral ratings are indirect measures of distinct attention systems that have different functional relations with the experimental events but that partially overlap in some circumstances'. Further studies seem necessary to decide which dependent variable is best suited for cognitive tasks assessing changes in attention across trials, such as the object‐examination task. The advantage of using mean HR would certainly be that this measure can be recorded in an objective way in different task contexts using objects, pictures, or even sounds as stimuli. The results presented here provide first evidence that it is possible to assess changes in mean HR across several trials, and that such changes are systematically related to behaviorally defined measures of attention. This opens a promising new avenue for analyzing infants' object categorization in studies referring to familiarization and novelty‐preference.</p> <hd id="AN0022816752-14">Acknowledgements</hd> <p>Much appreciation to the infants and parents who participated in this research. Thanks to Barbara Collins for collecting the ECG data, to Janna Pahnke for experimental assistance, and to our student research assistants for running the experiments and scoring the video tapes.</p> <ref id="AN0022816752-15"> <title> References </title> <blist> <bibl id="bib1" idref="ref22" type="bt">1</bibl> <bibtext> Behl‐Chadha, G. (1996). Basic‐level and superordinate‐like categorical representations in early infancy. Cognition, 60, 105 – 141.</bibtext> </blist> <blist> <bibl id="bib2" idref="ref16" type="bt">2</bibl> <bibtext> Colombo, J., Richman, W.A., Shaddy, D.J., Greenhoot, A.F., & Maikranz, J.M. (2001). Heart rate‐defined phases of attention, look duration, and infant performance in the paired‐comparison paradigm. Child Development, 72, 1605 – 1616.</bibtext> </blist> <blist> <bibl id="bib3" idref="ref17" type="bt">3</bibl> <bibtext> Colombo, J., Shaddy, D.J., Richman, W.A., Maikranz, J.M., & Blaga, O.M. (2004). 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New York: Macy Foundation.</bibtext> </blist> </ref> <aug> <p>By Birgit Elsner; Sabina Pauen and Susanna Jeschonek</p> <p>Reported by Author; Author; Author</p> </aug> <nolink nlid="nl1" bibid="bib13" firstref="ref2"></nolink> <nolink nlid="nl2" bibid="bib14" firstref="ref3"></nolink> <nolink nlid="nl3" bibid="bib17" firstref="ref8"></nolink> <nolink nlid="nl4" bibid="bib18" firstref="ref9"></nolink> <nolink nlid="nl5" bibid="bib10" firstref="ref10"></nolink> <nolink nlid="nl6" bibid="bib20" firstref="ref14"></nolink> <nolink nlid="nl7" bibid="bib15" firstref="ref15"></nolink> <nolink nlid="nl8" bibid="bib12" firstref="ref26"></nolink> <nolink nlid="nl9" bibid="bib11" firstref="ref27"></nolink> <nolink nlid="nl10" bibid="bib16" firstref="ref28"></nolink> <nolink nlid="nl11" bibid="bib19" firstref="ref37"></nolink>
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  Data: Physiological and Behavioral Parameters of Infants' Categorization: Changes in Heart Rate and Duration of Examining across Trials
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  Data: <searchLink fieldCode="AR" term="%22Elsner%2C+Birgit%22">Elsner, Birgit</searchLink><br /><searchLink fieldCode="AR" term="%22Pauen%2C+Sabina%22">Pauen, Sabina</searchLink><br /><searchLink fieldCode="AR" term="%22Jeschonek%2C+Susanna%22">Jeschonek, Susanna</searchLink>
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  Data: <searchLink fieldCode="SO" term="%22Developmental+Science%22"><i>Developmental Science</i></searchLink>. Nov 2006 9(6):551-556.
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  Data: Wiley-Blackwell. 350 Main Street, Malden, MA 02148. Tel: 800-835-6770; Tel: 781-388-8598; Fax: 781-388-8232; e-mail: cs-journals@wiley.com; Web site: http://www.wiley.com/WileyCDA/
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  Data: 6
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  Data: 2006
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  Data: Journal Articles<br />Reports - Research
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  Data: <searchLink fieldCode="DE" term="%22Metabolism%22">Metabolism</searchLink><br /><searchLink fieldCode="DE" term="%22Infants%22">Infants</searchLink><br /><searchLink fieldCode="DE" term="%22Classification%22">Classification</searchLink><br /><searchLink fieldCode="DE" term="%22Physiology%22">Physiology</searchLink><br /><searchLink fieldCode="DE" term="%22Task+Analysis%22">Task Analysis</searchLink><br /><searchLink fieldCode="DE" term="%22Attention%22">Attention</searchLink><br /><searchLink fieldCode="DE" term="%22Familiarity%22">Familiarity</searchLink><br /><searchLink fieldCode="DE" term="%22Measures+%28Individuals%29%22">Measures (Individuals)</searchLink><br /><searchLink fieldCode="DE" term="%22Cognitive+Processes%22">Cognitive Processes</searchLink><br /><searchLink fieldCode="DE" term="%22Behavior+Patterns%22">Behavior Patterns</searchLink>
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  Data: 10.1111/j.1467-7687.2006.00532.x
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  Data: 1363-755X
– Name: Abstract
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  Data: This report investigates the relations between duration of examining and heart rate (HR) across several trials of an object-examination task. A total of N= 20 11-month-olds were familiarized with a sequence of 10 different exemplars from the same global category (animals or furniture) before they received an exemplar from the contrasting category at test. Consistent with previous findings, HR was lower during states of focused attention (i.e. examining) than during states of casual attention (i.e. looking) or non-looking. Over the familiarization trials, examining stayed about the same, while mean HR increased. At test, examining increased and mean HR decreased, indicating that infants focused their attention on the out-of-category object. Psychophysiological and behavioral measures of attention were systematically related over trials, suggesting that heart rate provides a suitable objective measure to study infants' categorization performance in object-examination tasks.
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      – SubjectFull: Classification
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