Overload

If you want to improve your climbing then one thing you really need to consider in your training programme is overload. In that simply going to the climbing wall and doing the same session week in week out, simply isn’t going to lead to the sorts of improvement many of us are looking for. What you need to do is add a progressive overloading factor to you training regime.

There are several key ways to apply that overload
1. Frequency of training session – How often you go to the wall
2. Duration of training session – How long you climb for
3. Intensity of training session – How many routes you climb in a given time
4. Difficulty of training session – How hard the routes you are climbing are
5. Quantity of training – How many routes you climb in a session

It is arguable that different type of training will benefit from different type of of overload being applied. So for aerobic training frequency, duration, intensity and quantity of climbing sessions would be best, as with aerobic training we aren’t neccessarily trying to get pumped, which increasing the difficulty of the climbs might actually achieve.

Whereas, strength training would suit increases in the difficulty of the boulder problems that you are trying, whereas an increase in frequency or intensity, might not allow enough rest between training bouts for a suitable amount of recovery. Finally anaerobic training sits somewhere between the two, where we want to improve the difficult of the routes we are pulling laps on, as well as the quantity of the laps we are managing. Similarly reducing the length of rest between laps would up the intensity.

So think about how and where you can apply overload to your climbing and training

The Hottest Training Tip this winter?

A Season Ticket!

That’s right if you want a tip for how to improve your climbing this winter, then I can’t recommend anything more than getting a season ticket to your local climbing wall. What it means is that say you finish work and you have a spare hour or so, then rather than think well its too short a time to head to the wall instead, you’ll be heading up there for half hours sessions just to get your money’s worth.

Of course that is if you live a reasonable distance from the climbing wall, and don’t have kids you need to feed, wash, and put to bed. If things are all in your favour then climbing little and often is a great way to improve. As several hour long session a week gives you enough time to warm up, and then do some form of intense work out before heading home in time for tea and medals.

It also stops you climbing/training to absolute failure as many climber force themselves to climb until they develop the kind of pump and fatigue where you struggle to get the keys into the ignition of the car and changing gear is an activity you need a co-pilot for. Generally though training for climbing shouldn’t be that so intense that doing your shoes up becomes a task in itself. If you do you’ll find yourself getting technically messy, lossing contact strength and often become more likely to injure yourself as a result.

Do you Dream of White Horses or is it just a Goal?


We all have a dream, whether its to scale the 3000ft vertical cliffs of El Capitan or something closer to home like traverse across ‘A Dream of White Horses’ at Goagrth. Whatever you dream is there are various strategies to set yourself goals, some of which are more effective than others at helping you reach your Dream. So when is a dream just a goal, and how can you turn that Dream of White Horses into reality.

The psychologist have looked at goals in a variety of ways, to start with though they categorised them into different types of goals which are.
1. Outcome Goal or Dream – The final goal or dream – e.g. Climbing Dream of white horses.
2. Performance Goal – Some form of measurable performance – e.g. Climbing the Grade of E1
3. Process Goal – The processes that make the Outcome or performance goal possible – e.g. Placing gear, staying calm, good technique…

So whilst for instance having a Dream Goals is important to make sure that there is a light at the end of the tunnel that is your training program. The important thin g is the proximity of that Dream. Too far away and the light at the end of that tunnel is going to be awfully dim for an awfully long time. The worry is that this goal will just seem too far away, and rather than direct your attention and effort towards reaching it, you will find that you disengage from attempting to achieve it. A dream goal needs to be close enough that it feels achievable in the medium to long term.

So whilst you actual dream might be to climb Right Wall on Dinas Cromlech, you might find that that simply isn’t achievable in a year, as such you end up setting more overt mini dream goals with Right Wall being a more covert one, at the back of your mind, with the mini goals making stepping stones across each few months and eventually you’ll reach that major goal. One of those mini dream goals might be a performance type goal, like climb at least 10 routes of E4 over the summer.

The important thing to remember is this goal proximity, if you are close to achieving a goal then the behaviour that you have towards that goal radically changes. The best example I can give is a bouldering one. Imagine there are three problems, one you complete easily, the next you find impossible and will takes week to work out and develop the strength require to succeed, the third problem is just out of you ability to link, you can do all the moves and you believe it is possible. What you’ll find is that the effort and mental attitude you towards achieving the third boulder problem will be far more intense than, if you find something too easy or too hard.

The last type of goal I want to talk about is the process goal. These are the most powerful types of goal you can set yourself. Unlike the Dream or performance goal, which offer a distance focus on the horizon, something to look forward to if you like. However what is a goal like “I am going to climb ‘A Dream of White Horses’ this year”, actual going to do to help us actually achieve it. This is where the process goal comes in, where if you like you think through the processes that climbing your dream would involve and set many mini goals that build up your skills, confidence and fitness to eventually reach your dreams.

Often this setting of specific, measurable, attainable, realistic and time specific process goals is where people fail on there training regime. Often running head long into a regime of fitness training when maybe all they need was to work on their technique and ability to read routes! This is where the help of a coach can come in useful, assessing your needs and setting goals can be done through our online coaching

Learning Good Technique or Unlearning Bad?

Often people who want to be coached want to improve their technique, which in my mind is often the best way to make rapid improvements, as improving how you climb will improve your grade and confidence without the need for lengthy conditioning through aerobic, anaerobic or strength building regimes. Often where people fall down is how to develop good techniques, and this is where the science of skill acquisition can help.

At its simpliest level there are three stages to skill acquisition – Cognitve/thinking stage ; Associative or Intermediate stage; Autonomous or Elite Stage. If you then see this as a continum rather than seperate stages then we start off as a beginner, were we are first introduce to a skill, by practicing that skill we move from the first stages of learning where we are having to think about it all the time (hence cognitive stage), to where from time to time we will associate that skill with a given task, before after more practice we can carry out that skill without consciously thinking about (Autonomous Stage).

The key to moving from the cognitive/thinking stage through to the Autonous stage is effective practice. Now many people will have heard the saying practices makes perfect. Unfortunately this simply isn’t true, a modern coaching maxim is that only perfect practice makes perfect. So the chances are that unless you have used perfect technique from the very start of your climbing you will have some less than perfect technique that you will need to over write in your brain to adapt to better technique.

What often happens when learning new technique is that you practice it in an nice and easy environment, and then as soon as you try and use it in anger for the first time on the sharp end of a hard route is that it goes out the window, and you revert back to your old bad technique. This is because you haven’t practised it enough in the right type of environment.

Lets take for instance the habit of trying to face sideways when climbing, one of the quickest and easiest of technique to practice, and great help to your climbing. Try and climb keeping your upper body facing left or right as you climb. Now if you try and practice it on hard boulder problems then you simply won’t be able to practice it enough as you will get to pumped. If however you practice facing sideways as a technique drill every time you warm up on easy routes then you will effectively have more and more practice everytime you go climbing. After a few sessions try practicing that skill in a variety of situations e.g. leading easy routes, top roping hard routes, climbing corners, climbing arete, climbing slabs, climbing walls, etc… Adding in the different places and types of climbing that you practice the skill in help to make it a robust technique that will stay with you.

Remember though it won’t all happen over night as one researcher in sports science said ‘It take 10000 hours or 10 years of practice to reach an elite level in Sport’. So keep at it, as everyday is a school day when it comes to learning technique. I still use climbing drills during my warm ups!

Mental Skills: Making a Champion

There has been much research into what not only makes a good athlete but what makes Champion’s stand out from the crowd. Often they have looked at the amount of physical practice and training, finding that despite equal amounts, natural champions still end up on top. What research points to is that to make a champion, you need various mental skills that enable equal physique to be used to a much greater effect. The argument being that in order to make a champion you need to concentrate as much energy on training those mental skills and you do the physical and technical.

Williams & Krane (1993) highlight several key mental ingredients for champions including self-regulation of arousal, high self confidence, appropriate focus and concentration, positive preoccupation with sport, determination, commitment and that the athlete is in control. They also suggest for an athlete to achieve peak performance they go onto suggest several commonly used mental training techniques which are imagery, goal setting, thought control strategies (self-talk, CBT, Hypnosis), arousal management techniques, well-developed competition plans, coping strategies and pre-competition mental readying plans.

Whilst in climbing the physical side of training has been looked at extensively, in climbing the mental training techniques have been overlooked. One of the aims of this blog is to highlight many of these mental training techniques.

Williams, J and Krane, V (1993) Chapter 11 Psychological Characteristics of peak performance in Applied Sport Psychology: Personal Growth to peak performance, Ed. William, J. CA, USA, Mayfield Publishing Company.

Imagery – A new Outlook for Climbing

Typically imagery and climbing has been basic at is very best, often it has been misleading and based assumption brought from other sports and disciplines. One thing my MSc has shown me is that imagery is not a simple thing, and that there are many variables involved one of the models that tries to encompass all of them is the PETTLEP model Holmes and Collins(2001)

Before we go into the PETTLEP model it is probably best that we look at what imagery can be used for. In the most part climbers use imagery or visualisation to imagine themselves climbing a route. It ‘function’ is to aid sequence memory and improve performance once on the route. There are many other functions that imagery can be used for, like anxiety reduction, increasing confidence, aiding recovery from injury and aiding other mental skills.

If you see what you are imagining as a stimulus, then the function is often a combination of the meaning you attach to that stimulus and the response you give to it. Given time it is possible to control the stimulus, meaning and response to imagery. The way that you can start control your imagery is through using it regularly, which has been shown to be around 15 minutes a day.

This model advises athlete to look at and consider the:

PHYSICAL NATURE OF THE ACTIVITY
ENVIRONMENT YOU ARE TRYING TO REPLICATE
TIMING OF THE ACTIVITY
TASK YOU ARE LOOK AT REPLICATING
LEARNING YOU WANT TO ACHIEVE
EMOTIONS THE ACTIVE EVOKES
PERSPECTIVE YOU IMAGE IN

Each one of these will have certain considerations based on the sport, person, aim of the imagery intervention. However for simply visualising boulder problems research into climbing, and specifically bouldering points towards several key things that will help aid imagery. The first thing was discovered by my MSc supervisor Nicky Callow and Lew Hardy (1999, 2005) from SSHES, University of Wales Bangor.

What they found was that in bouldering tasks an External Visual Imagery Perspective (that is as seen by a documentry crew filming you) was better than an Internal Visual Imagery Perspective (seen through your own eyes). However better still was EVI with Kinesthetic Imagery (imaginging how it feels) was most effective.

They also found that for people with a higher imagine ability had more positive effect, and that whilst climber with lower imagery abilities didn’t benefit from the performance effects of Kinesthetic imagery they did find it increased there confidence in the task.

It not just as simple as that though as Craig Hall (1997) another one of the oracles of modern imagery research, believes that whilst research does point to various sports like climbing have a perspective that best suits the physical nature and type of task. The individual athletes preferred perspective needs to be the first consideration.

Hall, C (1997) Lew Hardy’s third myth: A matter of perspective. JASP, 9.
Hardy & Callow (1999) Efficacy of External and Internal Visual Imagery Perspectives for the enhancement of performance on Tasks in which Form is Important, JSEP, 21.
Hardy & Callow (2005) An Critical Analysis of Applied Imagery Research, In Handbook of Research in Applied Sport and Exercise Psychology: Internation Perspectives, WV, USA, Eds. Hachfort, Duda & Lidor.
Holmes & Collins (2001) The PETTLEP Aproach to motor imagery: A Functional Equivalence Model for Sport Psychologists, JASP 13(1)

How Confidence Can Improve Your Performance

Climbing is primarily a head game, admitting that you are in it for that moment of thrilling panic, as your breathe deepens and you face the only option, commit or fall. Crossing that line in the sand and facing life at its most primal, fight or flight! In that moment its not your strength or fitness that will get you through that dark alley, but you mind.

The thing is that today, you believe, you believe that you can do this, you’ve been climbing well all day. Each route a step up on the last one, you saw someone lead the route the last time you were at the crag, you know there’s gear above. A distant voice says ‘go for it’ as your stomach sinks. At that moment you move on and discover a new place, that ephemoral moment.

There are numerous theories, ideas, research and intervention that can at the very least make you aware of some of the components success or failure. This first situation could be numerous times in my climbing career that I have experience, be it when mine or someonelses confidence shines. This incident though occurred just after I heard of Bandurra, and his thoery of self efficacy.

….“Self efficacy refers to beliefs in ones capabilities to organize and execute the courses of action required to manage prospective situations. Efficacy beliefs influence how people think, feel, motivate themselves and act” Bandurra (1995).

In laymens terms efficacy is self confidence within a given task and/or environment, that given how confident we feel at that precise moment of commitment is linked to the choice of activity we choose, do we commit or back off? The amount of effort and persisitence we give to an attempt under the threat of failure, even how we think about the climbing and our emotional reactions.

Research has tracked down four main building blocks of self efficacy which in order of influence are prior performances, vicarious experience, verbal persausion and arousal level. What Bandurra theorises is that if you develop the building blocks of efficacy then it increases your own personal beliefs in your ability to achieve your goals, and then you can start to realise those goals.

Science aside I have witnessed many days when a series of progressively harder and harder routes have lead to the successful ascent of a new grade of a climbers, none more so compelling than just after I had seen the diagram of the building blocks of self-efficacy. I had arranged to meet up with two climbers Hazel and Sarah, I had never met them before, in the emails we exchanged I had come to know that they want to push themselves on Slate, and that they had previous lead E2.

Unlike teaching beginners these guys were climbers though, and at some point you need to accept the risk. As we warmed up on a few sports routes I started to climb and point out a few things they could do to save a bit of energy, but other than that there was minimal ‘traditional’ coaching.

Instead I used a progressive approach, making each route harder than the last. Eventually the girls decided that they both wanted to lead a burly E2 laybacking crack. I sat back and observed from a distance, Sarah the first person up looked a little shakey on the lead but managed it fine when she choose to commit. Hazel on the other hand climbed it smoothly and in control. Now I know there is an argument for having a visual beta, but under Banduraa’s theory this would be classed as vicarious experience, in that you saw someone achieve your goal, and an inner voice has turn round and said ‘I can do that’.

On its own that observation was nothing to write home about, however on the second route the order was reversed. So first up was hazel, this time she was the shakey one, and Sarah climbed with a lot more grace and style.

The second route was a bit more complex than that though, as well as looking at the vicarious experience, I was assuming that the previous routes would have also bolstered there confidence as a perforamnce accomplishments. On top of that I also started to turn the cogs of verbal persuasion The route was an E3 in the guidebook and the look on the two girl’s faces and body posture changed, E3 to them was a big thing. They undoubtably had the skills and ability to lead this route but the anxiety of breaking a new grade was undermining their confidence.

So I told them that as one of the authors of the fourthcoming guidebooks to the area we were downgrading the route to E2 5c, rather than E3 6a. After explaining why we downgraded the route, I climbed it and tried to make it look as easy as I could.

By now the colour had return to their faces, and after climbing the route successfully, I re-awarded them with the E3 tick, for which I receive two very big smiles, for a coach there is no bigger reward than the overt satisfaction of people you work with. My next stop was to see where exactly I could go with this, so we went on to another E3, this time I told them the grade, climbed the route, and them let them both lead it.

The next day one of them climbed Comes the Dervish, they both had “the best weekend climbing”. I did tell them a week later that I had observed and to a certain extent helped the process along by choose rotues to help develop there confidence in stages, both were fine with it, but the real question was it all because of self efficacy?

Whether it was or not, the main thing is that improving you self efficacy is so easy that you probably do it already, what this and the following articles want to highlight are ways that modern sports psychology can be used to increase our climbing performance. The lessons to take from this, and the lessons we are going to cover over the coming months are going to address ways that we can build the four building blocks of Bandurra’s Self-efficacy or your confidence in a climbing situation.

Prior Performance

The easiest way and by far the most powerful way to increase efficacy is by using your previous accomplishment to build up in a steady progression. It is a delicate line between make too rapider progression and failure or too slower progression and stagnation. Get it right and everything works for you, over step the line and the wheels will quick fall off the wagoon, and you will undoubtably have a negative effect on you confidence.

The trick is to know you ability, know the routes you want to climb and then create a step by step approach to your route. Be it routes of similar style, length, difficult. If you have a route as a goal then you will probably have done your homework and know the demands through reputation. Later in the series we will cover goal setting, but as a starter concerntrate on process goals, like feeling comfortable on route of certain grades, climbing efficiently or placing gear rather than success or failure on specific routes.

As well as recent performance expriences it is possible to recall through a process of imagery prior performance. Whilst we don’t cover this specifically when we address imagery, the ability to visualise prior performance experience can help reinforce confidence and even reduce anxiety.

Vicarious Experience

Like your performance accomplishment, vicarious experience can be gained both directly from observation of both your friends and others, but also through visualisation. One of the mechanisms that it undoubtably works through is our natural behaviour to judge performances against our own ability, so whilst watching someone who you percieve as better than you will still help to increase your efficacy, you often gain more when you witness someone who you percieve as the same level or even worse than you at climbing. The reason being that in the latter situation you mindset will change to, ‘if they can do it, so can I’.

In terms of real observations and the ethics of watching someone climb route prior to climbing it, many of the elite climbers of today work to a strict on-sight ethic, where they try and insist that they have onsighted the route, only in the rarest of circumstances is this true. They will have undoubtably acculumlated some vicarious experience, be it through watching a friend, or having someone elses description of the route by which they judge their own potential to perform. The only thing that is inportant ethically is that you are true to yourself.

Verbal Persausion

For most of us verbal persuasion will come from those around us, be it belayers or friends you are climbing with. The right thing said at the right time can have really positive effects on your performance, verbal encouragement has been shown to improve performance in a variety of laboratory settings as well as in real life situations.

You can try this out yourself, next time your at the wall try traversing on a angle of wall that will result in failure, firstly traverse back and forth until you reach failure but have no one you know with you noting down the time you can hang on for, the next time you try, either after a substanial rest or on another visit, go with your friends and get them to call out lots of encouragement as see if you last longer? I tried this exercise on a few young climbers, two of climbers almost doubled the amount of time they manage to climb for.

This link to encouraging to success, can be equally linked to negative encourage whether that be through the direct communication of what you belays says to the more subtle language of their body or facial expression. As a belayer it is an import to remember that and remember that in giving someone the time to belay them, attentively, positively and with ethusiasm, should be repaid in kind by the climber. If it is not then consider climbing with someone that does. I have climbed a few times with people who seem to fill me with negativity, I think I only ever climbed with them twice.

An obscure voice that often persuade us to carry on or give up is our inner voice. This chatter of our consciousness is what the boffins call this self-talk, and the research is in its infancy by comparison to other sport psychological interventions, but we won’t hear anymore about this for a couple of months.

Arousal

Arousal is a well researched area in sport, anxiety being one of the biggest obstacle and sometimes boosts to performance, as such research into the optimum aurosal levels for optimal performance in mainstream sports has created a drive to push research to answer some of these questions. Some of this research has used outdoor pursuits and climbing as it is easier to manipulate the anxiety levels, by having people lead or top-rope.

We will seperate our somatic from cognitive arousal and how these can effect our processing efficiency, conscious processing and even how they can cause performance catastrophies. On top of the causes and effects of arousals we will also examine ways to manage our arousal levels through relaxation, visualisation and self talk.

The thing to remember is you are in it for that moment of thrilling panic, as your breathe deepens and you face the only option, commit or fall off.

Online Coaching?

For many people getting a good climbing coach is difficult, if you live too far away from the large urban areas and especially London, then a coach rather than an instructor can be hard to find. In order to help address this and keep the cost of coaching down, here at Climbing Coach we are starting to offer individualised online coaching solutions via email, skype and MSM

How does it work?

Well the first session, which is a thorough needs assessment, where we identify you weakness, help you set training goals, and develop a few training activities to address those needs. This takes around one hour and cost £10.

If you’d like to find out more about online coaching then email Mark Reeves via his main webpage.

The Stretching Debate

Recently someone posted this article on UKC, printed in the New York Times, now you should instantly question the scientific validity of a journalist perspective on what in all likelihood is a review of a review of stretching. Whilst I don’t doubt Gretchen Reynolds scientific credentials, I do question her academic integrity, after all her editor wants ‘good’ copy, rather than a in depth analysis of all the stretching literature.

I suspect that whilst much of her advice is true, a look back at the research, and the actual findings bring much of the context into when that advice is actually applicable. Like most thing in life there are several caveats that can and should be applied to general laws or rules that are often applied to stretching.

In the NYT Article there are several points made that can be argued reasonably easily with a brief overview of research literature, however many of these are perhaps taken out of context, and may only apply to the Olympic athlete.

Stretching Reduces Muscle Strength
Now whilst this is true, we are only talking about a 2% to 5% reduction, these studies have only look at weakening directly after stretching. So unless you are an Olympic athlete about to go for gold then does such a small drop in performance really make than much difference to you.

Stretching Increases Muscle Strength
In direct opposition to this stretching reducing muscle strength, is that if stretching is performed regularly, but not immediately before activity. Has been shown to lead to a 2% to 5% increase if strength if carried out regularly.

Stretching Helps Prevent Injury
There is a great quote from the NYT article about stretching and injury prevention.

The largest study has been done on military recruits; results showed that an almost equal number of subjects developed lower-limb injuries (Shin Splints, stress fractures, etc.)”

This highlights one of the problem when it comes to interpreting scientific research. This statement however true is questionable because how do you expect stretching to prevent stress fractures, the only type of injury stretch might be expected to prevent can surely only be a skeletal muscle or soft tissue injury. Interesting the same military study did conclude that soft tissue type injuries were significantly reduce.

Again research points towards different effects regards when you stretch. So stretch immediately before activity has little to no effect with injury prevention, however regular stretching not prior to exercise has been shown to reduce soft tissue type injuries.

Warming up reduces injury
At present it would appear that warming up prior to activity is key, in that its purpose is to help increase heart rate, dilate the capillaries, warm up the muscles and speed up nerve transmissions. Current research suggest that prior to a main activity then stretching might not be of benefit for injury prevention and may reduce muscle strength.

However a small increase in muscle temperature has been shown to reduce the likelihood of a muscle tear in isolated rabbit muscles.

In terms of warm ups the current thinking is working between 40-60% of you maximum for as long as it take you to develop a light sweat. It will take a fitter person longer to achieve a warmed up state than a less fit person. An alternative to jogging or light exercise is a passive warm up that might take the shape of a hot bath or shower.

TAKE HOME MESSAGE
It may not be advantageous to stretch immediately prior to activity, as it doesn’t help prevent injury and reduces muscle strength.

Using stretching as a general activity, when not training can increase you range of motion and help reduce injury.

Warm up before any activity session.

Warm up passively or activity prior to stretch session

If you like to read a very good online article that covers the subject more fully then Ian Shrier has a online article here

Coaching in Adventure Sports

Many people consider coaching adventure sports to be different from coaching any other type of sports, and whilst this may hold true to a certain extent, the underlying coaching principles do still apply for adventure sports. What this mini article is going to do is explain a little of the scientific understanding of how we learn and why coaching adventure sports is different.

Firstly in order to learn we need to take in information, we do this via a short-term sensory store (STSS), which feeds our short term memory (STM) which in turn can eventually lead to us developing long-term memory (LTM). Various experiments have shown the STSS has the capability of holding a large amount of information, however most of it is filtered out or lost over time as it moves towards our STM.

In a classic experiment by Miller (1956) that looked at the limits of STM, in this experiment he found that we have a limit of 7+/-2 pieces of information and that it can be held there for around 30 seconds. More importantly for coaches he also found that you can chunk pieces of information together, so STM can hold 7+/-2 chunks of information. Where a chunk might be a group of movements that a climber or adventure sport has already learnt.

What this means for Coaches is that when we are teaching people we need to limit the information so that we don’t ‘overload’ our students. This is often best achieved through a progressive approach to teaching skills. Where adventure sports can differ from more mainstream sports is that anxiety and fear can play a large part in performance decline, through one of several hypothesised processes that will have an effect on those 7+/-2 chunks of information we can process.

One of the most popular processes related to anxiety is Processing Efficiency Theory (PET) developed by Eysenck & Calvo, (1992). PET states that when we are anxious our ability to process information is compromised by the anxiety that takes up processing power in our brain, what this means is that those 7+/-2 chunks of information are reduced, and the more anxious a person is the less information they will be able to cope with.

What this means is that as a coach in adventure sports we need to be able to see when someone is scare or anxious and perhaps remove them from that situation in order improve there ability to learn. An alternative approach is to slowly increase the stimulus that is inducing the anxiety, so in climbing that would be to do smaller routes or boulder problems first, before moving onto bigger and harder routes.

As such a progression in terms of not only difficulty of skill, but the environment in which those skills are being taught is important to the coaching of adventure sports. To view a more complete article on coach adventure sports please visit a fuller article on my website

Eysenck, M. W. & Calvo, M.G (1992) Anxiety and performance: the processing efficiency thoery. Cognition and Emotion, 6, 409-434.
Miller, G. (1956) The magical number seven, plus or minus two: Some limits on our capacity for processing information. Psychological Review, 63, 81-97.