A new perspective on how humans assess their surroundings; derivation of head orientation and its role in 'framing' the environment

Abstract

Understanding the way humans inform themselves about their environment is pivotal in helping explain our susceptibility to stimuli and how this modulates behaviour and movement patterns. We present a new device, the Human Interfaced Personal Observation Platform (HIPOP), which is a head-mounted (typically on a hat) unit that logs magnetometry and accelerometry data at high rates and, following appropriate calibration, can be used to determine the heading and pitch of the wearer's head. We used this device on participants visiting a botanical garden and noted that although head pitch ranged between -80° and 60°, 25% confidence limits were restricted to an arc of about 25° with a tendency for the head to be pitched down (mean head pitch ranged between -43° and 0°). Mean rates of change of head pitch varied between -0.00187°/0.1 s and 0.00187°/0.1 s, markedly slower than rates of change of head heading which varied between -0.3141°/0.1 s and 0.01263°/0.1 s although frequency distributions of both parameters showed them to be symmetrical and monomodal. Overall, there was considerable variation in both head pitch and head heading, which highlighted the role that head orientation might play in exposing people to certain features of the environment. Thus, when used in tandem with accurate position-determining systems, the HIPOP can be used to determine how the head is orientated relative to gravity and geographic North and in relation to geographic position, presenting data on how the environment is being 'framed' by people in relation to environmental content.

Keywords: Environmental framing; Head attitude; Navigation behaviour.

Figure 1. Schematic diagram of the construction of the HIPOP showing the constellation of the main components.

Figure 2. Image of participant wearing headmount containing HIPOP.

(A) The red arrow shows the tags positioned in the headband and (B) shows the HIPOP consisting of the Daily Diary, GPS and the battery outside the casing.

Figure 3. Head angle (A—pitch and B—heading) derived from the head mounted HIPOP in relation to the respective direct line of sight angles using data from participants (individuals shown by different symbols) asked to look at defined targets within a university quadrangle (see text for details).

Figure 4. Head pitch angle from four different subjects (differently coloured lines) walking down an unmarked corridor.

Note the small oscillations in the top trace due to individual strides.

Figure 5. Frequency distribution of head pitch angle from (A) four differenr subjects and (B) the same subject (subject W) performing the task four times, walking down an unmarked corridor.

The plots show marked inter-subject variation and minimal intra-subject variation.

Figure 6. Frequency distribution of rate of change of head pitch angle from (A) four different subjects (same as Fig. 5—denoted by letters) and (B) the same subject (subject W) performing the task four times, walking down an unmarked corridor.

As in Fig. 5, the plots show marked inter-subject variation and minimal intra-subject variation.

Figure 7. Example period of 30 s showing head directionality (A) pitch (B) heading and (C) both pitch and heading combined in a 3-dimensional plot, for a visitor walking through green space (the National Botanic Garden of Wales).

Note the characteristic oscillations in pitch between about 12 and 25 s (cf. Fig. 4).

Figure 8. Box whisker plot of the head pitch angles of the different visitors (denoted by letters of the alphabet) to the National Botanic Garden of Wales during the first 30 min after entering the exhibit.

Central points show means, boxes 25% confidence limits and vertical bars 95% confidence limits.

Figure 9. Frequency histogram of head pitch from example participants walking through the National Botanic Garden of Wales during the first 30 minutes after entry.

Figure 10. Frequency histograms showing rate of change of participants’ head pitch (black) and head yaw (grey) within the first 30 min enterering the National Botanic Garden of Wales (participants denoted by letters of the alphabet).

Figure 11. Frequency histogram of head heading (direction with respect to North = 0°) from example participants walking through the National Botanic Garden of Wales during the first 30 min after entry while they were walking in an approximately north-easterly direction (ca. 45°).

Figure 12. Visualisations of the trajectory of a visitor to the National Botanic Garden of Wales (red lines—determined using GPS) with head heading represented as lines extending from the trajectory.

(A) shows variation according to locality and (B) emphasizes the changes in head pitch that occur over the course of the walk (pitch-down is darker colours, pitch up, the lighter ones).

Figure 13. Hierarchy of rotating and non-rotating elements that determine the absolute head orientation and, beyond this, the elements that determine whether an object within the field of view afforded by the head orientation falls onto the fovea.