Session 2

The focus for this week was on tools, what they are and how they can be used. Both animals and humans use tools. Animals can modify the available things in their surroundings and fix them to use them as tools. Anything and everything can be used as a tool. Animals adapt to their environment and use it as tool too. For example, crows throwing nuts on main road to help them crack them open with passing cars. Chimpanzees using sticks to fetch honey. They pick up sticks, remove leaves, the size of the stick is as such that it can be sued properly. Once they are used, animals discard them. Choice and design of tool is very important and it depends on the purpose. Our interaction in a way with tools is on 6 levels, environmental, morphological, motor, perceptual, physio-motor and cultural.

·         The main focus of chapter 8 was to break down the practice of using tools.

o   Actions not gone as planned - errors

o   Ability to perform the action is missing - physical or mental inability to perform a task

·        Human error theorists talks about humans forming a part of a system and one person’s failure represents failure of the entire system. Similarly, tool usage can also be considered as a system of its own. Example of screw driver – 1. Environmental level (mode - poor access to screw driver, cause - door obscures access, consequence - constrained posture) 2. Morphological (mode – poor grasp of screw driver, cause poor grip arising from slippery handle, consequence – low torque)

·        A simple task can fail in variety of ways and failures are interconnected as well. Example, choosing knife instead of a screw driver – you can fail because of wrong selection, poor grip of hand and of the tool on the screw etc.

·       Cognitive psychologists prefer the term “slips” instead of “errors”. The study of slip suggests that human actions are hierarchical in nature. Example when writing any letter, define the word, then its shape, then the movement required and then the actual movement.

·        Two types of slippage, first is related to selection of the tool (discussed above) and second is between handle and hand. This could be physical inability to grab the handle or slippery handle.

·       Errors can lead to delay in work/frustration and injuries.

·       Most of the injuries during work happen due to sharp tools or tools that require use of a lot force.

·         Injuries and accidents from tools happen due to morphological and motor engagement. Meaning that people might use wrong tools for the task or wrong posture/grip to use the tool resulting in injuries.

·         Overexertion also leads to injuries. For example, holding a hammer for too long can give you trigger fingers. This can be reduced by using proper grips on the tools to reduce the vibration.

·         In short, there are three types of sources of failure – grip, posture and tool.

·         Not only physical constrains such as inability to use a tool can lead to errors but environmental factors also come into play. For example, if the environment is as such that you have to wear gloves then your ability to use a tool will also change.

·         Then the chapter discusses about neurological deficits and ways in which the representation of tool use in brain can become impaired. In doing so, the author talks about Apraxia: patients of this lose the ability to perform the sort of skilled actions that we take for granted in our everyday lives.  

·       Ideomotor Apraxia: Patients can identify objects and their use but cannot act it out. Example of this is making a cutting gesture from a knife. Patients with some damage in left hemisphere of their brain perhaps due to stroke, tumor or Alzheimer face this. Case Study – 72 errors out of 160 elicitation but all 72 errors were not completely wrong. For example, when asked about what you do with apple, they showed chewing only and not picking up an apple or biting it, just chewing. When asked about gun, they just reloaded it, did not point it at anyone which is quite stereotypical.

·         Ideational Apraxia: It arises due to not knowing which object to use i.e. errors in associating tools with actions. These people cannot act out a task but when confronted with a task can easily perform it. Also, they have an issue with sequencing and orders. Showing them photos and asking them assemble them might be a challenging task for them.

·         Neglect: Neglect patients do not have impairments; they are simply unable to attend to one side of their body by either ignoring the objects on that side or being unable to move within the space on that side. For example crossing Xs and 0s.