Temporal distribution of co-verbal hand movements

Temporal Distribution Movements

of Co-verbal Hand

Pierre Feyereisen Unitt de Physiopathologie

du SystPme Nerveux (FYPA),

The temporal distribution of hand gestures during lominute conversation samples was examined in 6 normal and 12 aphasic subjects. Run tests based on the presence or absence of gestures in successive lo-second periods showed that gestures do not occur randomly. Interpretation of this fact is based on complementary observations: (1) Signifkantly fewer gestures occur in the first 100 seconds of the conversation. (2) Gestures are significantly less frequent in the early moments when the subjects begin to verbalize after an experimenter’s intervention. (3) In the low gesticulation group, former gesticulation facilitates subsequent gestures and inhibit them in the high gesticulation group. (4) Gestures are facilitated by the hands-to-legs posture, and inhibited by the folded arms posture. Key Words: Hand

gestures;

Aphasia;

Verbalization.

INTRODUCTION Human

ethologists can only be astonished by the frequency with which nonverbal signals, especially hand movements, occur during speech. There are as yet no useful models to explain the causal and functional factors controlling the motor behavior that accompanies verbal activity (for a review, see Feyereisen, 1980). Since similar movements are rarely observed in other contexts, it might be said that verbal behavior is possibly in itself the factor responsible for the production of gestures. The difficulties experi-

Received September 22, 1980; accepted October 5, 1981. Address reprint requests to: Pierre Feyereisen, Service de Neurologie, UCL elles, Belgium.

1350, Avenue

Hippocrate,

B-1200

Brux-

UniversitC de Louvain

enced by the speaker in the verbal encoding process, manifested by hesitations (see Dittmann, 1972; Butterworth and Beattie, 1978) and in aphasic subjects (Feyereisen, 1982), are more particularly related to gestural onsets. However, in the control mechanism of gestures, linguistic factors are not the only ones to be considered. Large interindividual and intercultural variations in gesture production have already been noted (see for example Sainsbury and Wood, 1977). The contention of this article is that postural facilitation of gestures can be established, that is to say, that gesture probability (1) is increased by the previous occurence of gestures and (2) is intluenced by the posture the subject has adopted. In order to test these hypotheses, the temporal distribution of gestures was analyzed during short conversations, of approximately ten minute periods, recorded with normal and aphasic subjects (subjects with a language disturbance following left cerebral hemisphere damage). The purpose of observing aphasics was firstly to study the influence of focal brain lesions on the organization of gestures. Its disturbing effects on language is already known. In another paper (Feyereisen, 1982), it has been shown that Kimurals (1973a, b) assumption, that gesture and language depend on common cerebral mechanisms, is not supported. On the contrary, it was found that, in spite of language disturbances, aphasic subjects produced more gestures than did normals. This reveals a dissociation between verbal and nonverbal expression. However, regardless of the reason for such motor behavior, aphasics’ gestural enhancement provides us with a means of testing the influence of different motivational levels of gestures on the temporal or1

Ethology and Sociobiology 3: l-9 (1982) 0 Elsevier Science Publishing Co., Inc., 1982 52 Vanderbilt Ave., New York, New York 10017

0162-3095/82/010001-tWO2.75

2

Pierre Feyereisen

ganization of co-verbal activity. In this paper, three groups of subjects are considered, differing by the amount of gestures they produce. It will be seen that the behavioral sequences are not identical in the different groups, suggesting that postural facilitation is not an independent factor but one whose effect depends on the influence of other causal variables on gestures. Statistical analysis of the temporal organization of co-verbal movements will be based on incidental observation, leading to the suppositions that (1) gestures do not occur randomly during the observations periods, (2) gesture probability is reduced at the beginning of the conversation, (3) there are fewer gestures occuring when a subject begins to talk just after an intervention by the experimenter, and (4) gesture frequency is influenced by the presence or absence of gestures occurring in the preceeding moments and also the kind of posture the subject has adopted. Statistics will be independently calculated in each of the three groups (low, middle, and high gesticulation levels). No attempt will be made to compare these groups other than by visual examination of the data. There are too many demographic differences between the groups. Although gesture production was never found to be related to sex, age, socioeconomic level, motivation to engage in the interview, Table 1. Characteristics

Subject

state of being hospitalized, or kind of aphasia, the role of these factors cannot be excluded as variables determining gestural behavior. Each subject will thus be his or her own control.

METHOD Subjects

Eighteen subjects were observed. Their principal characteristics are given in Table 1. Six normal subjects recruited in the hall or in the cafeteria of the hospital were asked to volunteer their participation in “an experiment on language.” Five of them belonged to the uppermiddle class, one to the lower class. All were self-reported right-handers. The twelve other subjects were selected from the hospitalized neurological population in the Cliniques Universitaires St-Luc in Brussels. The selection criteria for inclusion in the sample were evident language impairment in spontaneous speech, good physical state, and ability to sustain a conversation. The clinical type of aphasia was assessed by the neuropsychological team of the hospital. Neurophysiological and neuroradiological examinations (EEG, CT-Scan) showed left hemisphere lesions. The etiologies were CVA in ten cases, and brain tumor and trauma

of the Sample

Sex

Group I (low gesticulation s4 M S5 F s2 M s3 M J.V. F Sl M

Age (yr)

Neurological impairment

Relative verbalization duration

Relative gestures duration

level)

Group II (middle gesticulation A.K. M J.T. M H.V. F M O.C. S6 F A.L. M Group III (high gesticulation M A.M. J.P. M E.B. M E.D. M Y.L. F V.V. M

71 65 63 57 47 69

Normal Normal Normal Normal Wernicke’s aphasia Normal

0.95 0.92 0.68 0.88 0.61 0.95

0.06 0.07 0.12 0.14 0.15 0.20

level) 55 51 71 49 64 36

Amnesic aphasia Broca’s aphasia Wernicke’s aphasia Wernicke’s aphasia Normal Conduction aphasia

0.46 0.45 0.80 0.58 0.84 0.81

0.22 0.23 0.29 0.32 0.36 0.38

Broca’s aphasia Wernicke’s aphasia Broca’s aphasia Dysarthria Dysarthria Wernicke’s aphasia

0.73 0.78 0.61 0.84 0.75 0.78

0.40 0.44 0.45 0.48 0.52 0.69

level) 68 48 81 66 50 39

Temporal

Distribution

for the two remaining cases. Time since onset was generally short (about 1 month in 11 cases, and 20 months in the last case-Y.L.). Three subjects were right-hemiplegic: J.V., E.B., and Y.L. All normal and aphasic subjects were French-speaking. On the basis of the observed proportion of the conversation period during which one hand or both hands together were moving (see behavioral notation below), three groups of six subjects were constituted: I, II, and III (corresponding to a low, middle, and a high gesticulation level, respectively).

Experimental

Situation

Subjects were individually observed. They were invited to sit on a chair without armrests, with the exception of two hemiplegic patients who were sitting on a wheelchair. Subjects were facing a camera. The experimenter was sitting on their side with a 120” orientation, on their left side for three normal subjects and for the aphasics, on the right side for the three other normal subjects. He kept his hands in his pockets to prevent himself gesticulating. The normal subjects were told they constituted a control group for a language deficit study and that a short conversation would be recorded. The proposed topic was to tell how they passed an ordinary day. For the aphasic subjects, an attempt was made to have similar conditions, and the conversation was oriented toward their stay at the hospital, their work, and their family. For all the subjects, the experimenter asked questions and made comments to sustain their verbal expressions, but he did not discuss the content. Conversations duration was about 10 minutes (mean duration 641.7 seconds). Videotaped recording began immediately after the end of the instructions, i.e., f 5 minutes after meeting the subject. The field of the camera included a clock giving time with a precision of 1 second.

Behavioral

3

of Gestures

Notation

A transcription of the 18 videotaped recordings was made on five parallel lines. These lines correspond to the following: 1. Time-one unit per second. 2. Subject’s verbal behavior-onset and termination of verbal productions. For this anal-

ysis, interruptions shorter than 2 seconds were not taken into account; relative duration of verbalizations was the verbalization duration divided by the observation duration. Experimenter’s verbal behavior. Subject’s right-hand behavior: onset and termination of movements and postures. For the purpose of a statistical analysis, the different movements were categorized as follows: (1) gestures, i.e., all speech-focused movements that do not clearly belong to the other categories-they are often free of body- or objectcontact, except when subjects are speaking of themselves or of their own body parts; representational as well as simple accompaniement movements are considered as gestures; (2) automanip&tions, head and neck contacts, whatever their duration; (3) miscellaneous activity, other automanipulations, drumming movements, and so on. The postures adopted by the subject were also collected and grouped into three categories, according to the body part touched by the hand-P1 = hand-to-hand posture, P2 = hands-to-legs or to abdomen posture, P3 = folded-arms posture. Other postures rarely occurred. Subject’s left-hand behavior (noted as in 4). An example of the recording is presented in Figure 1. The relative duration of the nonverbal movements was calculated by summing the behaviors of the two hands (right hand only + left hand only + both hands together) divided by the observation duration. The relative duration of the postures was calculated by considering only the moments where both hands were motionless.

RESULTS

The four hypotheses stated above were successively tested: randomness of occurrence of gestures, reduction of gesture production in the beginning of the observation, reduction of gesture production just after an intervention by the experimenter, and sequential effects of gesture occurence.

Randomness

of the Sequences

of Hand Gestures

times were divided into 10 second periods. For each of these periods the recording

Observation

4

Pierre Feyereisen

10

0

Time

I....I...

Subject% verbal

.I

20

30s

I

I

I

. ..[....I...

I

I

behaviour

E’s verbal behaviour

R. hand

I

I

L. hand

consisted of coding “ - ” when no gesture occurred, and “ + ” otherwise. The Run test (Siegel, 1956) was applied to individual data, to examine whether sequences of + and - signs were random or not. Since the number of periods with or without gestures was greater than 20 for each subject, a Z approximation was used. In group I (low gesticulation level), Z values were -0.75, -5.20, -0.83, -1.58, -0.94 and -2.48. The negative values are due to the fact that the observed number of “runs” (i.e., sequences of identical signs) was less than expected. Individual results were combined in a single Z score by the formula (Rosenthal, 1978): Z rota,

=

c zw*, i=l,n

where i indexes subjects. The total Z score for group I was -4.81 (p 5 0.001). In group II (middle gesticulation level), Z values were - 1.53, +0.12, -0.43, -1.46, +0.56, and - 1.26. The total Z score was - 1.63 (p 5 0.052). In group III (high gesticulation level), Z values were

Figure 1. Example of the transcription method (see explanations in the text). Presence/absence of verbal behavior of the subject and of the experimenter are represented by up/down movement of the pen. Symbols for nonverbal behaviors are n= gestures, lAJ = automanipulation, W = miscellaneous movements, and PI, P2, P3 = postural immobility. Onset means the beginning of an unimanual or bimanual gesture.

- 1.99, -0.94, -2.20, -0.56, -2.17,and +0.41. The total Z score was - 3.04 (p 5 0.001). There is a significant trend, especially in groups I and III, for gestural or nongestural periods to occur in contiguity instead of randomly. The explanation for this may have been found in the subsequent analyses.

Comparison of the First 100 Seconds with the Remaining Part of the Interview

For each subject, the proportion of gesture duration during the first 100 seconds of observation

Temporal

Distribution

was compared to the proportion during the remainder of the interview, by means of the Wilcoxon T test. Differences were significant in the three groups (Table 2). However, these results may be due to the fact that the duration of the verbalization was also reduced at the beginning of the interview and therefore the subject was given less opportunity to gesticulate. Another T test was made of the gesture-duration-to-verbalization-duration ratio, comparing the first 100 seconds with the remainder of the interview. The differences in group III, where the reduction of the verbalizations in the beginning of the interview was also the greatest, tended not to be significant, but the same results as in the first test were obtained for groups I and II. It is therefore concluded that the probability of gestures is reduced at the beginning of the interview, and this fact could account for the nonrandom distribution of the gestural periods sequences.

Subject’s Reaction to the Experimenter’s Verbal Intervention For each subject, the 15 seconds of verbalization during which the subject begins to talk after an experimenter’s verbal utterance was considered. The probabilities of gestures in the three consecutive S-second periods were individually calculated and compared by means of the Friedman test. In the three groups, the proportion of gestures in the first 5-second period was significantly reduced [in group I, the probabilities were, respectively, 0.10, 0.16, and 0.16 (xZ2 = 6.33, p I 0.05); in group II, the probabilities were, respectively, 0.36, 0.44, and 0.42 (x2* = 6.33, p 5 0.05);in group III, the probabilities were, respectively, 0.37, 0.58, and 0.69 (xZZ = 9.33, p 5 O.Ol)]. It is suggested that subjects Table 2. Comparison

5

of Gestures

often (almost always) interrupted their gesticulations when the experimenter was speaking, and that a delay was necessary before a new onset of gesture. Further study is needed to examine whether a similar reduction in gestures can be observed when subjects begin to talk after a silent pause without an experimenter’s intervention (these events were rare in the present study), or when subjects begin to discuss a new topic.

Sequential Analysis As we can see from recent publications, the interest of many ethologists is focused on the statistical analysis of behavioral sequences (Morgan, 1976; Cane, 1978; Douglas and Tweed, 1979; Pruscha and Maurus, 1979; Rechten and Femald, 1979; Rodger and Rosenbrugh, 1979; see also Chatfield and Lemon, 1970; Slater, 1973; and Bakeman, 1978). However, a methodological problem exists in these studies in that a behavior is defined by the termination of another behavior. For instance, in the present study the so-called frequency of postural states depended on the number of times a gesture interrupted the postural immobility. Moreover, the stationarity assumption of Markov’s model is not met (point 2 above). Therefore, a method inspired by Sackett’s lag sequential analysis (Bakeman, 1978), and also following a suggestion of Slater and Ollason (1972), was adopted. The observations were transcribed as a succession of behavioral states, one per second. The different states were the behaviors defined in our method section. The onsets and terminations of gestures were considered, whatever their duration. Let us call Ni the number of such events per subject (unimanual and bimanual onsets are

of the First 100 Seconds (a) with the Remainder

of the Interview

(b): Mean for the Six

Subjects in the Three Groups; Results of the Wikoxon T Test Group I a b

’

Relative duration of gestures

Relative

duration

of verbalizations

Gestures/verbalizations

ratio

0.08 0.13 T=2

Group II a b 0.24

0.30

Group III a b 0.32

0.53

p 5 0.047

T=O p I 0.016

T=O p 5 0.016

0.78 0.83 T=6 N.S.

0.63 0.66 T=.5 N.S.

0.66 0.77 T=O p 5 0.016

0.10 T=

0.37 T=

0.48

0.16 1

p 5 0.031

0.46

1 p 5 0.031

0.68

T=3 p 5 0.076

6

added; when the two hands did not begin a bimanual gesture at the same moment, but with a delay superior or equal to 1 second, two onsets are counted). The subjects behavioral states were considered before and after the gesture at t_SO, t_lo, t_S, t_2, t+2, and t+5r i.e., the observed states 50, 10, 5 or 2 seconds before the onset and 2 or 5 seconds after the termination of gestures. t _ , and t + , were not chosen because gestures cannot appear at these moments and the probabilities of behavioral states must be differently calculated; t-50 was a control condition (no effect was expected). Let us call X, the number of times the behaviorj is observed in the subject i before and after the gestures, at the given time lag. The probability pij of observing this behavior was estimated by the proportion of the duration the behavior j tilled in the observation of the subject i. Hypotheses were made about the fact that X, would be greater or lower than the expected value (N&u). The expected and observed frequencies of the behavioral states were compared by means of the Wilcoxon T test. A test is made per group (N = 6), per time lag, and per behavioral transition. These tests are not independent, but the observations in each test are (this is another advantage of the method). I successively discuss (a) the autotransition between gestures and gestures and (b) the transition between other behavioral states and gestures. Autotransition of Gestures. The proportion of gestures among the behavioral states before the onset and after the termination of gestures is shown in Figure 2. In group I (bottom), more gestures than expected were observed from t_ 1o to t+S. The Wilcoxon test results were the following: at t_,O, T = 2, p 5 0.094; at t-5 and t+5, T = 0, p 5 0.016; at te2 and t+2, T = 2, p 5 0.047; at t-5O, T = 9, N.S. In groul I, there was no apparent difference between observed and expected frequencies. The only significant results occurred at t_5o (T = 0, p 5 0.016), where there were more gestures than expected, and at t+2 (T = 2, p d 0.047), where there were less. The absence of a marked effect in this group could be related to the fact that the result of the Run test was less significant in group II than in the other groups. In group III, the observed frequencies of gesture were inferior to the expected ones. The difference was significant at t _2 (T = 1, p 5 0.03 I),

Pierre Feyereisen at t+2 (T = 0, p 5 0.016) and at t+s (T = 0, p 5 0.016). Reversed trends appear therefore in groups I and III. In the low gesticulation group, the onset of gesture could be facilitated by the previous occurence of gestures, while in high gesticulation group, the termination of gesture was followed by behaviors other than gestures. The Spearman correlation between the differences (observed frequency minus expected frequency from the negative to the positive) and the relative duration of gestures was quite significant (rs = -0.83, N = 18, p 5 0.001). It is thus shown that subsequent effects may be facilitatory or inhibitory according to the gesticulation level. More concretely, we might suppose that in group III, where almost all verbalizations were accompanied by gestures, gestural termination was associated with an experimenter’s verbal intervention, and fewer gestures could thus occur. Transition Between Other Behaviorai States and Gestures. Since no great differences appear

between the various groups, the mean results can be presented for the three pooled groups (Figure 3). The hand-to-hand posture (Pl) seems to have had no effect on the onset of gesture. The only significant results were in group II at t- 5 (T = 0, p I 0.016) and at t+5 (T = 2, p I 0.047), where less Pl states were observed than expected. But no test made on the 18 pooled subjects was significant. Only three subjects displayed the hands-tolegs posture (P2) in group I. Tests were conducted on groups I and II pooled, on group III and on the whole sample (N = 15). In groups I + II, significantly more P2 states were observed than expected at L2 (T = 8, p 5 0.098), t+2 (T = 5, p I 0.020) and at t+5 (T = 9, p I 0.064). In group III, the same effect was noted to a greater extent (T = 0, p I 0.016 at t_,, t+2, and t+5). For the whole sample, a trend was apparent in the same direction at t_5 (T = 30, p I 0.086), and the tests at t_2, t+2, and t+5 were highly significant (p I 0.004). The P2 posture seems to have been facilitated therefore by the termination of gesture, while in turn itself facilitating the onset of gesture at short intervals. On the other hand, the folded arms posture (P3) was less frequently associated with the gestures than expected. Since this state was only represented in eight subjects (four in the group

Temporal

Distribution

7

of Gestures

SC

.u

30

,‘--

/

.20 /

/

/

/

/

/

\

--_

/

’ __--_~-_----_-__------------~~~-/ f

\

\

\

\

\

f

-1

JO

I, three in the group II, and one in the group III), a single test was made for them. Significant effects were observed at all intervals except one: 1_5o (at t_io, z_~, and tP2, T = 1, p 5 0.008; at t+2, T = 3.5, p 5 0.025; at t+5, T = 7,p 5 0.074). The frequency of automanipulations and miscellaneous movements (A + M) was only slightly modified before and after occurence of gesture. In group I, significant effects were observed at t+2 (T = 0, p I 0.016) and at t+5 (T = 3,~ 5 0.078), where fewer movements than expected

Figure 2. Observed probabilities of behavioral states before and after gestures: autotransition of gestures. I, II, III: expected probabilities of gestural states in the low gesticulation group (bottom), the middie gesticulation group (middle), and the high gesticulation group (top), respectively. t-so, etc.: time lag before onset and after offset of gestures. were noted. No effect appeared in group II. In group III, more movements were observed than expected at t_5 (T = 3, p I 0.078), t_2 (T = 3, p 5 0.078), t+2 CT = 1, p 5 0.031), and t+5

8

Pierre Feyereisen

~:______,-----:

d------+-,

____________-_____-__

Is

1 ,., ‘-50

t

-10

‘-5

“2

n

’

‘-2

‘-5

(T = 3.5, p 5 0.010). Reversed trends thus appear in groups I and III, but the expected levels do not differ to any great extent (0.15 and 0.13, respectively). The test made on the whole sample (N = 18) revealed a significant effect at t_* (T = 35, p 5 O.OlS), where more movements than expected were observed. Other results were not significant. Nongestural movements could thus have a slight facilitatory effect on the production of gestures.

DISCUSSION This study has shown that (1) gestures are not randomly distributed across the duration of the conversation, (2) fewer gestures occur at the beginning of the conversation, (3) there is a latency period for the occurrence of gestures when the subject begins to talk after having listened to the experimenter, (4) the occurrence of gesture influences the probability of subsequent gestures, but opposite trends are observed in the low and high gesticulation groups, and (5) the posture adopted by the subject influences the production of gestures-they are inhibited by the arms folded posture and facilitated by the hands-to-legs posture. Except for the fourth point, the groups do not differ to any great extent. The results are consistent in that they suggest a firing mechanism could elicit the gestures only after a delay, during which the subject speaks without gesticulating. After the first onset, if

-cyTFr

10

5

‘-2

1.2

‘3

Figure 3. Observed probabilities of behavioral states before and after gestures: (a) hand-to-hand posture (PI), (b) hand-to-legs postures (P2), (c) folded arms posture (P3), (d) automanipulation and miscellaneous movements (A + M); the horizontal lines represent the expected levels (mean probabilities for the 18 subjects). t-50, etc.: time lag before onset and after offset of gestures.

gestures are poorly motivated (as in the low gesticulation group), the previous occurrence of gesture facilitates the gesture onset. This could not be possible, however, for the enhancement of gesture in the high gesticulation group, where facilitation is not observed. I hypothetize that, in the control mechanism of gestures, nonlinguistic factors, such as postural facilitation, could determine the temporal structure of gesture production as well as the preference for one hand (Feyereisen, 1977). In suchcircumstances, an analysis of the formal properties of the verbal utterances which are accompanied by gestures would not give any result. If this hypothesis could be supported, an argument would be provided for a vestigial function of gestures, which would always be optional in the behavior of the speaker. Special attention would have to be paid to the factors which disinhibit gestures, and the circumstances arising with the occurrence of the first gesture of a sequence would have to be examined. My analysis has shown the importance of careful observation in studying human behavior.

Temporal

Distribution

9

of Gestures

tion: rules for grooming in flies. Animal Behavior

It is suggested that formal models

such as those developed by Dawkins and Dawkins (1973,1976) could be applied to the study of gestures. The postural facilitation hypothesis could be analyzed in different behaviors such as grooming in flies, pecking in chicks, and co-verbal activity

in man. Without any assumptions about the possible analogy or homology of behaviors, the ethological paradigm may be valuable in providing a fresh look at certain human behaviors and in suggesting a choice of tools with which to study them.

24: 739-755

Behavior

27: 1236-1252

(1979).

Feyereisen, P. PrCf&ence manuelle pour les diff&ents types de mouvements accompagnant la parole. Journal de Psychologie 74: 451-470 (1977). -.

This research was partially supported by a grant of the Fonds de DCveloppement Scientifique (FDS) of the University of Louvain. We are grateful to Professor Laterre, who kindly gave us access to the neurological service of the Cliniques Universitaires St-Luc in Brussels, and we are also indebted to Professor Meulders and to Xavier Seron, Raymond Bruyer, Dominique Rectem, and Jacques Schouppe for their helpful assistance.

(1976).

Dittmann, A.T. The body movement-speech rhythm relationship as a cue to speech encoding. In Studies in Dyadic Communication, A.W. Siegman and B. Pope (Eds.). New York: Pergamon, 1972, pp. 177-210. Douglas, J.M., Tweed, R.L. Analysing the patterning of a sequence of discrete behavioral events. Animal

normale

et pathologique

Determinants des signaux non-verbaux: perspective tthologique. Psychologica Belgica 20: i-32 (1980).

-.

Manual activity during speaking in aphasic subjects (in press). Kimura, D. Manual activity during speaking: I. Righthanders. Neuropsychologia 11: 45-50 (1973a). -. Manual activity during speaking: II. Left-handers. Neuropsychologiu 11: 51-55 (19736). Morgan, B.J.T. Markov properties of sequences of behaviors. Journal of the Royal Statistical SocietyC 25: 31-36 (1976).

Pruscha, H., Maurus, M. Analysis of the temporal structure of primate communication. Behavior 69: 118-134 (1979).

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Rosenthal, R. Combining results of independent studies. Psychological Bulletin 85: 185-193 (1978). Sainsbury, P., Wood, E. Measuring gesture: its cultural and clinical correlates. Psychological Medicine 7, 63-72 (1977). Siegel, S. Nonparametric Statisticsfor the Behavioral Sciences. Tokyo: Mc-Graw Hill-Kogakusha, 1956, pp. 52-58. Slater, P.J.B. Describing sequences of behavior. In Perspectives in Ethology, P.P.G. Bateson and P.H. Klopfer (Eds.). New York and London: Plenum, 1973, pp. 131-153. Slater, P.J.B., Ollason, J.C. The temporal pattern of behavior in isolated male zebra finches: transition analysis. Behavior 42: 248-269 (1972).