1. Six Types of Problems:
Equal: Items moved back and forth; rows identical at end in length and density
Length: One row longer, equal density
Density: Equal length, one row has more buttons (greater density)

2. Conflict-length: One row longer, other row more dense; longer row has more buttons
Conflict-density: One row longer, other row more dense; denser row has more buttons
Conflict-equal: One row longer, other row more dense; equal numbers of objects

3. Cognitive Development (Re-cap)
Current state of the field is characterized by multiple theoretical perspectives
In some cases, these perspectives attempt to explain the same phenomena (e.g., object understanding from a Piagetian versus a core-knowledge perspective; development of number conservation from a Piagetian or information processing approach)
Often, theoretical perspectives address different aspects of cognitive development
Therefore, the extent to which they are compatible or contradictory remains unclear and their explanatory value is difficult to evaluate
Researchers have called for greater unification of theoretical perspectives