Visual Analogue Scales (VAS) have been used in clinical and research settings to continuously monitor a range of subjective sensations for example, pain, depression and appetite . These measures provide valuable information on sensations that are difficult to monitor using alternative methods . VAS typically take the form of 100 mm horizontal lines anchored at both ends by extreme subjective feelings . This horizontal line represents a continuum and allows the participant to place a mark on the scale reflecting the intensity of a subjective sensation at a particular time (i.e. state). This allows the sensation to be measurable and quantifiable. The interpretation of VAS is simple since the descriptive terms are already present . Traditionally, VAS were administered using pen and paper (P&P), which were quick and relatively easy to use. Data collection from P&P method is often time-consuming since each line needs to be measured and manually inputted into a spreadsheet individually introducing the possibility of human error. Whilst the use of P&P method has limited flaws when the participants are closely monitored, in free-living situations P&P method has considerable limitations for example when unsupervised, compliance is low  and questions may be omitted, wrongly marked or not filled in at the correct time resulting in invalid data .
To diminish the problems of using P&P, a step was taken to develop the same system of VAS on portable handheld computers, which became the appropriately named Electronic Appetite Ratings System (EARS). The transition to the use of handheld computers was driven by their relatively inexpensive cost and their associated practical benefits . Additional benefits of electronic versions include the use of an audio alarm as a reminder of when the VAS needed to be completed, leading to compliance rates of 90% or better . All entries are date- and time-stamped. The first EARS to be developed used a VAS software program which was designed to administer VAS using a Psion hand-held personal digital assistant (PDA) (©University of Leeds, UK). The software employed a 100 mm horizontal line with a vertical marker present at the mid-point. The arrow keys are used to move the cursor left or right to a particular position. A pilot study was conducted to compare the EARS with the standard P&P method . Two different energy pre-loads were used to manipulate subjective appetite sensations. The results demonstrated that the mean area under the curve (AUC) ratings were similar between the two techniques, however there were significant differences between the techniques when some of the ratings at individual time points were compared (i.e., immediately before and after meals). Both techniques detected a significant difference between the high and low energy lunches . The use of EARS was later compared to P&P in a clinical population of haemodialysis patients. For all questions, there was a bias towards lower scores on the EARS than P&P. Due to the unsystematic pattern of variation in the data and the high standard deviations giving wide limits of agreement, these factors suggest that there is limited amount of agreement between the methods and they therefore should not be used interchangeably .
Using a similar methodological approach, an alternative EARS was developed using the Apple Newton Message Pad, (©RJ Stubbs and M Elia) to administer the VAS. The main development was that participants used a 'stylus' to mark their responses on the screen of the Apple Newton - which is more akin to placing a mark on a paper VAS using a pencil. Two validation studies were conducted using EARS Newton to compare with the P&P [5, 10]. The first compared the response of subjects (10 men, 10 women) after consuming meals at fixed time points. The meals were of fixed energy density, energy and nutrient content. The participants completed hourly VAS using both methods on day 1, which was then repeated after two intervening days (i.e., on day 4). The second study examined validity and reliability in a free-living environment rather than the laboratory. Both studies demonstrated that the temporal pattern of oscillations in subjective appetite sensations and the sensitivity remained similar. However, there were significant differences in hunger and fullness ratings at the extremes of the VAS, with the EARS Newton resulting in more constrained values than P&P. Bland and Altman analysis revealed that the mean difference between the two methods was significantly different to zero due to higher variance seen in the P&P method than EARS Newton. In the test-retest studies there were no significant differences in individual hourly ratings or AUC between the two techniques. Since both studies show the same differences between P&P and EARS Newton, and the same reliability, the authors concluded that EARS Newton is a valid method for administering VAS, both in controlled and free-living settings but it is not interchangeable with P&P.
Whybrow et al, (2006) have recently developed the EARS Newton system to make use of a Palm-handheld computer. The VAS software was identical to the previous studies of Stubbs except the screen size and length of VAS displayed was different. This study included (10 men, 10 women) using a similar test day design to Stratton et al, (1998) as previously described. There was an interaction between gender and method. Women tended to rate their appetite sensations higher when using EARS Palm than P&P for 3 of the VAS questions (i.e., hunger, desire to eat and prospective consumption). There was a statistical bias between the methods for 5 VAS questions leading to the conclusion that EARS Palm showed sensitivity and similarities to P&P, but cannot be used interchangeably.
Due to a series of technical issues and a halt in their manufacture, the Psion PDA has become obsolete. Using a similar approach, new software was developed for a different EARS (HP iPAQ 214) (©Queensland University of Technology (QUT)). The aim of the present study was to validate the new EARS II against the gold standard P&P and the previously validated EARS in standardised conditions.