lecture one human computer.docx

**The human** **Introduction:** In 1983, Card, Moran and Newell described the Model Human Processor: a simplified view of the human processing involved in interacting with computer systems. MHP comprises 3 subsystems: the perceptual system, the motor system and the cognitive system. Each of them h...

**The human** **Introduction:** In 1983, Card, Moran and Newell described the Model Human Processor: a simplified view of the human processing involved in interacting with computer systems. MHP comprises 3 subsystems: the perceptual system, the motor system and the cognitive system. Each of them has a processor and memory. MHP also includes a number of Principles of operation which dictate the behavior of the system under certain conditions. **Input-output channels** In interaction with a computer, the human input is the data output by the computer vice versa. Input in humans occurs mainly through the senses and output through the motor controls of the effectors. Vision, hearing and touch are the most important senses in HCI. The fingers, voice, eyes, head and body position are the primary effectors. 1. **Vision** Visual perception can be divided in 2 stages: the physical reception of the stimulus from the outside world, and the processing and interpretation of that stimulus. The eye is a mechanism for receiving light and transforming it into electrical energy. Light is reflected from objects in the visual field and their image is focused on the back of the eye, where it is transformed into an electrical signal and passed to the brain. 2. **Hearing** The ear receives vibrations on the air and transmits them through various stages to the auditory nerves. 3. **Touch** The apparatus of touch (haptic perception) is not localized. Stimuli are received through the skin, which contains various types of sensory receptors. Mechanoreceptors, responding to pressure, are important in HCI. 4. **Movement** When making movements, a stimulus is received through the sensory receptors and transmitted to the brain. After processing, the brain tells the appropriate muscle to respond. **Human memory** We can distinguish 3 types of memory: sensory buffers, short-term memory (or working memory) and long-term memory. 1. **Sensory memory** The sensory memories act as buffers for stimuli received through each of the senses: iconic memory for vision, echoic memory for sounds and haptic memory for touch. These memories are constantly overwritten by new information coming in on these channels. Information is passed from the sensory memory into short-term memory by attention, filtering the stimuli to those that are at that moment of interest 2. **Short-term memory** STM is used to store information which is only required fleetingly. STM can be accessed rapidly, however, also decays rapidly. It has a limited capacity. Miller stated the 7+/-2 rule, which means that humans can store 5-9 chunks of information. Chunks can be single items or groups of items, like 2 digits of a telephone number grouped together. Patterns can be useful as aids to memory. 3. **Long-term memory** LTM differs from STM in various ways. It has an unlimited capacity, a slow access time and forgetting occurs more slowly or not at all. Information is stored here from the STM through rehearsal. There are 2 types of LTM: episodic memory and semantic memory. Episodic memory represents our memory of event and experiences in a serial form. Semantic memory is a structured record of facts, concepts and skills that we have acquired, derived from the episodic memory. **Thinking: reasoning and problem solving** Thinking can require different amounts of knowledge. Some thinking activities are much directed and the knowledge required is constrained. Others require vast amounts of knowledge from different domains. Thinking can be divided in reasoning and problem solving. **Reasoning** Reasoning is the process by which we use the knowledge we have to draw conclusions or infer something new about the domain of interest. There are different types of reasoning: deductive, inductive and abductive. ***Deduction:*** Deductive reasoning derives the logically necessary conclusion from the given premises. The logical conclusion does not have to correspond to our notion of truth. The human deduction is weak at the points where truth and validity clash. ***Induction:*** Inductive reasoning is generalizing from cases we have seen to infer information about cases we have not seen. In practice, induction is used to fill in missing details while reasoning. ***Abduction:*** Abduction reasons from a fact to the action or state that caused it. Abduction is used to derive explanations for the events we observe. **Problem solving** Problem solving is the process of finding a solution to an unfamiliar taste, using (adapting) the knowledge we have. There are different views on problem solving: ***Gestalt theory:*** The Gestalt theory states that problem solving is both productive and reproductive; insight is needed to solve a problem. However, this theory has not been accepted as "sufficient". ***Problem space theory:*** The problem space comprises problem states and problem solving involves generating these states using legal state transition operators. People use these to move from the initial state to the goal state. Heuristics (e.g. Means-end analysis) are employed to select the right operators. ***Use of analogy:*** Problems are solved by mapping knowledge relating to a similar known domain to the new problem: analogical mapping. **Skill acquisition** Experts often have a better encoding of knowledge: information structures are fine-tuned at a deep level to enable efficient and accurate retrieval. According to the ATC model, these skills are acquired through 3 levels: - The learner uses general-purpose rules which interpret facts about a problem. (slow, memory-demanding) - The learner develops rules specific to the task, using proceduralization. - The rules are tuned to speed up performance, using generalization. - There are different types of errors: changes in context of skilled behavior can cause errors. An incorrect understanding/model of a situation can cause errors too, because humans tend to create mental models, based on experience, which may differ from the actual situation.